CULTURAL PRACTICES

 

 

LEARN HOW PLANTS GROW

 

In this chapter and most of the following chapters, the technical knowledge presented is for your benefit as a worker with plants.  Some of you as salesper­sons will also be dealing with customers.  In most cases, little will be ac­complished in using technical terms; however, you must understand the technical terminology that other people use to express it.

 

It is impossible to cover completely each of the subject matters to be dis­cussed.  Additional, easily available reference material will be cited for your fur­ther enlightenment.

 

To understand how plants grow, one must first understand their structures and the functions of the various parts.  This involves roots, stems, leaves, and reproductive parts.  There is a great variation in appearance of these plant parts as found throughout the plant kingdom; however, their basic functions remain the same.

 

 

 ROOTS

 

In a normal, healthy plant there is a balance between the shoot system and the root system.  This balance is disturbed by root loss during transplanting or through improper cultivation.  The balance can be restored by pruning some of the top (shoot) growth of the plant.  If this is not done, the plant may be set back or die because the roots are unable to supply the tops with adequate moisture and nutrients.  Root loss during transplanting is much greater in bare root trees and shrubs than in container plants.

 

There are two kinds of root systems found in plants, the fibrous root system and the tap root system.  The fibrous root system consists of a great many, much-branched roots that are slender and fiber-like; no one root is more prominent than the others.  Most of our nursery plants have this type of root system.

 

The tap root system consists of one main root that grows directly downward, from which branch roots arise.  The main root may be a fleshy, food storing or­gan (carrot), or a more or less woody root (oak, citrus).  Tap roots generally penetrate much deeper in the soil than fibrous roots, thus tap rooted plants are much more difficult to transplant.

 

     The functions of the root system are absorption, anchorage, conduction and storage.

 

In land plants, large amounts of water are absorbed through millions of thin-walled root hairs in close contact with the soil particles.  Each root hair is formed from a single epidermal cell near the growing tip of the root.  Each one lasts only a short time, and many are killed during transplanting, causing some plants to wilt because water loss is greater than intake.  Little water absorption occurs through the epidermis (outer cell layer) of older roots where root hairs are no longer present.  Special care must be given during transplanting, and roots should be exposed for no longer than absolutely necessary.  In the nursery, they should be heeled-in with moist sawdust or soil until sold or transplanted.  The customer should be told about the effects of drying the roots of a plant.

 

Anchorage is gained by the extensiveness of the root system (spread and depth).  Plants are more resistant to being blown over by the wind, and less sus­ceptible to damage by cultivation when soil conditions allow roots to grow into the soil.

    

Plants that have become root-bound within their containers also need special attention.  The roots should be spread out or pruned if they are found to be spirally coiled around themselves.  Such a plant may strangle itself within a few years.

 

Plant nutrients (inorganic fertilizers) must be in a soluble form so they

can easily pass through the cell walls into the plant and be carried to the leaves for manufacture into usable food.  Any plant receiving fertilizer should be well watered so that the fertilizer is diluted throughout the root zone.  An excess of fer­tilizer can result in a burning or browning of the foliage.  This is a result of water shortage in the foliage due to its movement out of the plant root when surround­ing soil contains too high a concentration of fertilizer.  The foliage is actually dried out.

 

 

 STEMS

 

The primary functions of the stem are support, conduction and storage. Since the stem holds the leaves up, they receive more light, which is important in the manufacture of plant food.  Some plants have a single stem, often called a trunk, with various methods of branching.  Others have many stems arising from the root crown.  The interior, dense hardwood of older stems is dead and serves only for support.

 

Conduction is the moving of water, mineral solutions and plant food. Water and mineral solutions move upward from the roots to the leaves through inner tissues called xylem.  Manufactured food from the leaves moves out of the leaves through outer stem tissues called phloem.  Between the xylem and the phloem is a tissue called the cambium layer, which forms new xylem and phloem as may be required by the plant.

 

STEM CROSS SECTIONS

 

Not all plants have the same arrangement of xylem, phloem and cambium. In monocotyledonous (single seed leaf) plants, the three tissues are formed in bundles scattered in a discontinuous vascular system throughout the stem.  (Example:  corn, grass).

 

In the dicotyledonous (2 seed leaves) plants and gymnosperms (many seed leaves), the xylem is formed on the inside next to the heartwood, surrounded by a continuous layer of cambium, with the phloem on the outside.  (Example: most trees, shrubs, annual and perennial plants.)  The cambium forms new xylem on the inside as an annual ring, or cycle of growth, and new layers of phloem on the outside of the cambium layer.  The older layers of phloem form the bark on trees and shrubs.

 

It is important to prevent damage to the cambium layer.  This could be caused by wire too tightly tied to stake up a plant, plastic rope used to ball up a plant's roots, or mechanical damage such as bruises and cuts.  The first two conditions can kill a plant if unchecked, and the third can be an open invitation for insects and plant diseases.  It may also predispose a plant to winter injury.  When a stem is completely girdled, the phloem cells below the girdle no longer receive food from the leaves.  Therefore, all leafless parts below the girdle will be starved.  A girdle is a complete circle of dead tissue around the stem, which interrupts the supply pipeline.

 

SPECIALIZED STEMS AND ROOTS

 

Some plants have stem and root structures modified so that they hold excep­tionally large amounts of stored food and also function as asexual reproductive structures.  Some of the growth patterns in modified stems  are quite complex and involve changes from vegetative growth to reproductive development and back again.  These growth cycles are usually controlled by changes in temperature, al­though moisture may be the controlling factor for tropical plants.  Bulbs and corms are examples of modified stems that function in this way.  Some of our most popular horticulture plants are propagated by the use of bulbs, corms, rhizomes, tubers (modified stems) and tuberous roots.  Lilies, tulips, hyacinths, narcissus, Dutch iris, and many more early spring flowers develop from bulbs.  Crocus, colchicum, and gladiolus all have corms. German, or tall, bearded iris; lily-of-the-valley; and orchids send up leaves and flower stalks from rhizomes.  In addition, grass is planted using sprigs, or stolons, and strawberry plants are ob­tained from the ends of runners.  Potatoes are planted by using pieces of tubers.  All of these are also modified stems.  Interestingly, all but the strawberry and potato are members of the monocotyledon subgroup of flowering plants.

 

The structure of each of these is slightly different, but all except tuberous roots have nodes, comparable to those on a typical stem.  Buds form at these nodes, as on a typical stem.  A true bulb, such as a daffodil, consists primarily of fleshy modified leaves containing stored food.  The stem, or basal plate, is a very compressed structure; e.g., the hard part cut off of the bottom of an onion in preparing it for cooking is the basal plate.  Each scale leaf has arisen from a node on this plate.  Usually a new growing point appears in the axil of about every fourth leaf.  In some bulbs a growing point can occur at each axil (point where a leaf joins the stem).  New growing points are initiated in the fall and normally one continues to develop during spring while the old mother bulb is flowering.  After flowering, the old bulb gradually disintegrates (in most cases) as the new bulb scales enlarge and develop.  In order to have successful flowering the next year, foliage leaves must be maintained as long as possible to provide a source of carbohydrates to be stored in the new bulb.  A relatively cool growing season fol­lowing bloom is ideal but not what we can ordinarily expect in the Southeast.  This explains why commercial production of bulbs and related structures is not feasible in our area.  It is also helpful to feed and water bulbs following flowering to help maintain vegetative growth as long as possible.  Corms, such as gladiolus, differ from bulbs in that they are solid stem structures with remains of dried scale leaves surrounding and protecting them.  Nodes can be seen if these dried leaves are removed.  Again, the cycle of changes is controlled by temperature. During the time the mother corm is flowering, a new corm is developing at its top.  By fall there is only a small shriveled remnant of the mother.

A period of relatively warm (not hot) weather is necessary to initiate changes from vegetative growth to reproductive development within the bulb.  However, the bloom will be produced until after a period of exposure to temperatures around 40 degrees for about 8 to 12 weeks.  Following this, bloom stalks will develop in bulbs like tulip or daffodil when warm temperatures again prevail.  As already mentioned, the changes in some cases are controlled by differences in moisture.  This is typical of species that have developed in tropical areas where seasons

are wet-dry rather than hot-cold.  The large so-called Dutch amaryllis is an example of a plant that goes dormant in response to dry conditions.

 

A rhizome such as German iris is essentially the main axis or stem of the plant in a horizontal position under ground.  Its development is less complex than that of bulbs and corms.  Leaves and bloom stalks arise either from the growing apex or from nodes farther back.  Following bloom, that particular section of the structure disintegrates, but others have been developing to take its place.  The dif­ferences between rhizomes and stolons are not clear. Some authorities consider any cylindrical horizontal stem a rhizome if it is normally found below the soil sur­face, or a stolon if it is above ground. However, in describing the development of tubers as in the case of Irish potatoes, the tuber is most often considered the swol­len subapical portion of a stolon.  We take advantage of the food storage function of potato tubers by including them in our diet.  In order to propagate potatoes, we cut up the tubers to include at least one "eye", which is actually a node containing a bud.  Each piece should contain enough stored food to supply the new shoot un­til it can function on its own.  New roots arise adventitiously from the base of the new shoot.  What we have done is propagate by taking stem cuttings. The original tuber is often referred to as a "seed" potato.  Obviously, it is not a seed, which is produced in the ovary of the potato flower.

 

Although these specialized stem structures can be divided so the pieces contain buds that will develop into new shoots, storage roots, on the other hand, do not have nodes and buds.  Sometimes adventitious shoots will develop if the roots are subjected to proper conditions.  Sweet potatoes (true roots) are subjected to high temperatures, which seem to overcome what is called "proximal dominance," and shoots are then produced along the entire length of the tuberous roots.  However, in many cases no shoots are produced unless a portion of the crown, the area where stem and root tissue meet, is included with the root.  This propagation method is referred to as crown division.  Dahlia is an example of a plant that must be propagated in this way.  Unless the tuberous root is cut so that the top end includes a portion of the crown with a bud, no shoots will develop.  Stored food in the root is used in the development of the new shoots.  During the grow­ing season, new storage roots are formed at the base of the new shoot as the old ones gradually disintegrate.  What we have, then, is a biennial root (living through two growing seasons) and an annual top (living through one growing season).  It should be noted that fibrous plant roots behave somewhat differently and often can be used for root cuttings, which will develop shoots.  Shoot produc­tion occurs readily in many species.  It is easy to root plants that "sucker", that is, normally send up shoots from the roots.

 

Wide variations of the basic patterns of development are found in the dif­ferent plant species.  It is important to learn as much as possible about each plant with which you work.  Frequently, questions arise about the possibility of forcing spring flowering bulbs into bloom in the house.  Temperature control is very dif­ficult in the average home, and results are rarely successful.  Most florists buy preconditioned bulbs prepared by specialists using precise temperature regimes re­quired for each species.  Only then can bloom be expected to compare with that found when the plant is growing in its native habitat.

 

Outdoor planting of crocus and narcissus, including the large trumpet daf­fodils, can be done from September until the ground freezes.  Results with these are quite satisfactory in most of our area except for the extreme southern regions.

 

Tulips and hyacinths are somewhat less successful and are best treated as annuals.  Scales on the lily bulb are less protected than are those of tulip, hyacinth and nar­cissus and must be handled more carefully.  They should not be allowed to become dry.  They are very subject to fungus and virus diseases, so are very difficult to maintain successfully in the warm, humid Southeast.  Iris, daylilies and anemones are good garden flowers for the Southeast.  All underground storage structures are subject to fungus and other soil-borne diseases.  It is very important to plant in well drained, sunny locations.  In heavy clay soil, do not plant as deep as is recom­mended for soils containing more sand or organic material.  A large dollar volume of plant sales in the fall comes from sale of spring-flowering bulbs.  It is helpful and important to know something of their growth habits and requirements.                                                                  

 

 

PLANTS WITH SPECIALIZED STEMS OR ROOTS

 

 I.  Spring flowering.  Hardy, planted in the fall.

 

     A.  Amaryllidaceae - Amaryllis family

 

         Bulbs

 

         Allium sp.* - Ornamental onion

         Galanthus nivalis - Snowdrop

         Leucojum vernum - Spring snowflake

         Narcissus pseudo-narcissus - Daffodil

         N. incomparabilis - Short cup narcissus

         N. jonquil - Jonquil - usually fragrant

         N. tazetta - Polyanthus narcissus

         N. poeticus - Poet's narcissus

 

     B.  Iridaceae - Iris family

 

         Bulbs

 

         Iris reticulata - Early fragrant iris

         Iris xiphium - Spanish and Dutch iris

 

 

         Corms

 

         Crocus vernus - Large Dutch crocus

         Crocus - Many others, beginning in January

 

         Rhizomes

 

         Iris germanica - German, or tall-bearded, iris

 

     C.  Liliaceae - Lily family

 

         Bulbs

 

         Hyacinth orientalis - Hyacinth

         Muscari spp. - Grape hyacinth

         Tulipa gesneriana - Common garden tulip

         Tulipa fosteriana and hybrids - Include large 'Red Emperor' variety

         Tulipa kaufmaniana - Water-lily tulip

         Tulipa species - More than 150 others

 

         Rhizomes

 

         Convallaria majalis - Lily-of-the-valley

 

       D.  Ranunculaceae - Buttercup family

 

           Tuberous root

 

         Anemone coronaria - Poppy anemone

 

         A.  Blanda - Sapphire anemone

 

II.  Summer and fall flowering (1.  Hardy.  Fall planted).

 

     A.  Amaryllidaceae - Amaryllis family

 

         Bulbs

 

         Lycoris squamigera - Pink surprise lily

         L. radiata - Red surprise lily

 

     B.  Iridaceae - Iris family

 

 

 

         Corms

 

         Crocus autumnale - Autumn crocus

 

         C. specious and others - Fall flowering crocus

 

     C.  Liliaceae - Lily family

 

         Bulbs

 

         Lilium regale - Regal lily

         L. candidum - Madonna lily

         L. speciosum - Includes variety 'Rubrum'

 

         Many more Lilium species and hybrids, often difficult to grow in

         the Southeast.

 

         Corms

 

         Colchicum species

 

         Rhizomes

 

         Liriope sp. - Turf lily

 

         Tuberous root

 

         Hemerocallis fulva - Day lily

 

 III. Summer and fall flowering (2.  Tender.  Dug and stored in fall, planted

      spring).

 

     A.  Amaryllidaceae - Amaryllis family

 

         Bulbs

 

         Amaryllis vittatum - Large flowering amaryllis

         Hymenocallis americana - Spider lily

 

     B.  Araceae - Arum family

 

         Tubers

 

         Caladium bicolor - Elephant ear and caladium

 

     C.  Cannaceae - Canna family

 

         Rhizomes

 

         Canna generalis - Canna

 

     D.  Compositae - Daisy family

 

         Tuberous root

 

         Dahlia pinnata - Dahlia

 

     E.  Iridaceae - Iris family

 

         Corms

 

         Gladiolus gandavensis - Gladiolus

 

*sp. - species, meaning many different ones; some may be of unknown parentage.

 

 

 

 

 

 

 LEAVES

 

The most conspicuous organs of plants are their leaves.  Leaves are varied as to their arrangement on the stem, their form, the distribution of their veins (venation), their structure, and many other characteristics.  Leaf characters are used extensively in the description of the species; however, reliance cannot be placed on them alone, since their appearance is easily changed by environmental conditions.  Generally, leaves of dicotyledonous plants vary from leaves of monocotyledonous plants.  A typical leaf of a dicot* generally has netted vena­tion, one or more prominent veins with branches forming a conspicuous net, while monocots* have parallel veined leaves with inconspicuous branching between the veins such as in corn.

 

(*Accepted abbreviation for dicotyledons and monocotyledons plants,

  respectively.)

 

        Leaves have two main functions, photosynthesis and transpiration.

 

The leaves on most plants are the chief food manufacturing organs through the process called photosynthesis.  Photosynthesis may be briefly defined, as the process whereby carbon dioxide (CO2) and water (H2O) are transformed by energy from visible light absorbed by chlorophyll (green pigments).  During daylight hours, this process of food manufacture (photosynthesis) results in oxygen being given off by the plants.  The clean, fresh air in parks and planted areas is what makes them so pleasant.  We are dependent upon green plants for the oxygen we breathe.

 

It is through the leaf that almost all of the water is given off to the atmos­phere by the aerial parts of the plant in the process of transpiration.  The water balance of a plant is determined by the relative rates of absorption through the roots and transpiration from the leaves.  If loss of water is more rapid than ab­sorption, a water deficit occurs.  A deficit in any part of a plant may cause wilt­ing, mostly seen in leaves.

 

The conducting tissue, xylem and phloem, makes a continuous pipeline from the roots through the stems and into the leaves.  The veins, which form a network throughout the leaves, are part of this pipeline.  Water movement from the roots through the vascular system to the leaves depends on lower water pressure at the top of the plant.  This pressure difference occurs as a result of transpiration (loss of water from leaves).

 

In addition to providing the mechanism for water movement through a plant, transpiration serves another purpose.  During the process, evaporation of water from the leaf reduces leaf temperature and helps prevent injury from excessive heat build-up.

 

 

 

 

 

FLOWERS AND CONES

 

Horticulturally important plants, with few exceptions, produce seeds. This characteristic puts them in the most highly developed group of the plant kingdom.  This group is subdivided into two groups:  the angiosperms meaning "covered seed," and the gymnosperms, meaning "naked seed."  Plants in the first group bloom and develop fruit which encloses the seed, while those in the second group have no true flowers or fruit but bear their seeds uncovered in cones of similar structures.  This group includes the conifers, such as pines, the ginkgo, and a few others of importance to us.

 

Conspicuous because of their bright colors, flowers come in many sizes and shapes as well as colors.  Their principal value to the retail nurseryman and the customer is ornamental.  Flowers are also used extensively in the description of the species.  Their structure is less visibly affected by environment than is the structure of leaves and stems.

 

The flower may be thought of as a specialized stem with leaves adapted for reproductive functions.  The following structures are present in a flower that has all the characteristic parts:

 

      1.  An outer set of green floral leaves (sepals), which enclose the other parts of the flower until these are nearly mature.  Collectively, the  sepals comprise the calyx.

 

     2.  An inner set of colored or white floral leaves (petals) constitute the corolla.  In many flowers, the petals are showy and may aid in attracting the atten­tion of insects that assist in pollination.

 

     3.  Within the petals, one or more sets of stamens (staminate or "male" flowers).  Stamens are composed of pollen-bearing anthers supported by a fila­ment.  When the pollen is mature, it is discharged through the ruptured anther wall and is carried by insects or the wind.

 

     4.  At the center of the flower, one or more pistils (pistillate or "female" flowers).  Pistils consist of an ovule-bearing base (or ovary) supporting an elongated region (or style) whose expanded tip (or surface) is called the stigma.  The ovule gives rise to the seed.  The mature ovary becomes the fruit.

 

     5.  These flower parts are borne on an enlarged portion of the flower-supporting stem called the receptacle.  Pollination takes place when the pollen grains are transferred from the anther to a stigma.  Some plants are self-fertile (Italian plum), and are able to use their own pollen, or pollen from another plant of the same type.

 

Others (many cherries and apples) need pollen from an entirely  different variety (cross pollination).  In addition, some species have male and female flowers on separate plants; and in order to produce fruit, the female plant must have a male plant, or pollinizer, nearby -- hollies and aucuba, for example.

 

 

A cone can also be considered a specialized stem with leaves adapted for reproductive purposes.  However, it does not have the typical flower parts. Ovules and pollen are borne on separate cones, which are quite different in appearance.  The conspicuous cones are the ovule bearing, or female cones. The ovules lie on one of the modified leaves, called a cone scale, and are not surrounded by ovary tissue.  Pollen is borne on much smaller cones and is carried by wind to the ovule.  Following pollination, the scales of the cone close so that the ovule is protected while the pollen grain germinates and fertilization of the egg cell occurs.  This may take as long as a year.  When the ovule matures into a seed, the scales again open and the seed is released as from a pine cone.

 

 

FRUITS

 

The botanical term "fruit" refers to the mature ovary and other flower parts associated with it.  It may include the receptacle as well as withered remnants of the petals, sepals, stamens, and stylar portions of the pistil. It would also include any seeds contained in the ovary.

 

SEEDS

 

A seed is a miniature plant in an arrested state of development.  Most seeds contain a "built-in" food supply.  Structurally, the seed is a matured ovule, al­though various parts of the ovary may be incorporated in the seed coat.  Plants naturally perpetuate themselves from the seeds that develop from their flowers.  In the nursery industry, we are concerned with the flower itself and its color, beauty and fragrance, rather than the seed or fruit produced by plants such as azalea and marigold.  We do like to see fruit on pyracantha and holly.  Many of our plants have been bred so that they either produce unreliable seed or may not produce seed at all.  This is especially true with annuals and vegetables; the hybrid seed from which they grew is a result of controlled pollinations.  Were a person to collect and plant the seed from a hybrid petunia or tomato, the resulting plants would resemble the original parental types without many of the desirable characteristics of the hybrid.

 

The fact that seeds are really whole plants in a miniature form and in a dormant state will help you understand why seed loses viability (ability to grow) and are no longer good.  The "miniature plant" has actually "outgrown" its dormant period without receiving conditions for continued growth (planting) and, there­fore, has died.  The period of time different kinds of plants will stay alive in the dormant (seed) stage ranges from a few weeks to many years.  Package dating is used by most seed firms to prevent sale of "old" seed.  The proper care of the seed lengthens its life considerably and we now see grass seed in vacuum-packaged containers, which add months to its keeping quality.  Conversely, seed racks exposed to dampness, heat and temperature extremes usually reduce the time seeds on the rack will remain viable.

The life-cycle of a seed-bearing plant is divided into two broad phases, vegeta­tive and reproductive. The vegetative phase consists of two stages, the germina­tion of the seed (or rooting of a cutting) and vegetative growth.  Although the ger­mination phase may take only a few weeks, the period of vegetative growth may last for years, with repeated growth cycles.

 

The reproductive phase begins with certain physiological changes indicating flower, or cone, bud induction, followed by flower bud initiation and develop­ment, then flowering with the subsequent production of fruit and seed.

 

 

VEGETATIVE REPRODUCTION

 

Many plants reproduce by means other than seeds such as runners, tuberous roots, tip layering, and underground stems.  Man takes advantage of these methods and adds a few others such as budding and grafting to produce either more of the same plant or a new combination of two or more plants.

 

     Layering -- The development of new plants by roots forming on a stem that is still attached to the mother plant.  The rooted part is then separated from the mother plant.  Strawberries and raspberries are naturally occurring examples.  Layering is not generally a nursery practice.

 

     Division -- Many plants increase in growth at the crown and produce new shoots from the base.  As pointed out earlier, these shoots form roots and may be separated as single new plants, or the entire plant may be separated into sections.

This method is particularly valuable for the propagation of herbaceous perennials.  Division is usually done in the fall or spring. Examples are chrysanthemum, shasta daisy, and pampas grass.

 

     Separation -- Bulbs, corms, tubers, and rhizomes are all similar in being under­ground stems which can produce additional plants.  Tulips form small bulblets, lilies form scales, gladiolus form small corms, and dahlias form new tubers.  These may be removed from the parent plant after blooming and then planted at the proper time.  It may take two or three years to produce a mature plant from some of these immature parts.

 

     Cuttings -- Most woody plants are propagated by cuttings.  This technique or dinarily assures the grower of obtaining a new plant just like the original in all respects.  Cuttings may be made from many parts of a plant, such as the stem, leaf or root, and are taken from different plants at various times of the year.  Most cuttings need a humid atmosphere, warm soil temperatures, light and a moist, but well-drained soil medium.  Plant hormones are often used to accelerate rooting (Fig. 4).  A mist bed is commonly used to provide moist conditions.

 

     Graftage -- This is the joining together of two different plant parts in

that they will fuse and continue growing as one unit.  The upper portion is the scion, while the under part is the stock (rootstock, understock). Grafting is done to produce plants that don't reproduce well or "true" by other means (selected dog­wood cultivars, pecan).  Special effects also are possible, such as "tree roses" and weeping cherries.  Some graftage is necessary because certain soil pathogens make it difficult to grow some plants on their own roots.  Fruit trees nowadays can be artificially dwarfed by the use of special rootstocks which impart a dwarfing ef­fect on the scion.  Whatever the purpose of grafting, a successful take depends on how well the cambium layers of the scion and stock match up.  Often, the graft can be detected by a slight swelling or a difference in the two barks.  Once a graft union has healed, any suckers arising from the root stock should be removed.

 

     Budding -- This is a type of grafting.  A growth bud from one plant is im­planted under the bark of another of a related variety.  "Four way apple trees" are produced this way.

 

 

GROWTH CHARACTERISTICS

 

One of the questions asked by many of the customers coming into the nursery is "how large (or how tall) does it grow?"  While most trees and shrubs have a maximum under good growing conditions, this growth may not be reach for many, many years  A large number of the trees and shrubs can be maintained at much lower height or size by controlling growth with  selective pruning.  For example, Photinia fraseri  (Red Top) may eventually reach twenty feet in height; yet, this plant is used in many locations where it is held to a certain height.  A large num­ber of the trees and shrubs can be maintained at a much lower height or size by controlling growth with selective pruning.  For example   (Red Top) may even­tually reach twenty feet in height; yet, this plant is used in many locations where it is held to a height of 6 to 8 feet for a period of years.  Possibly, the best answer for the customer is to describe a plant as low growing, medium or tall, and ex­plain some of its possible variations.  It should also be remembered that each plant is an individual, and its response to environmental conditions may be quite different from another plant of the same species growing nearby.

 

Many of the plants found in our gardens and in the nursery originate in other states and in foreign countries that have similar climate to our climate in the Southeast.  The more nearly one's garden duplicates the climate of the plant's original home, the better the plant will grow.  The average gardener's great problem is trying to grow plants that are not adapted to the conditions found in his garden.

 

Each plant found in nature has, over the centuries, adapted itself to certain climatic conditions -- sunlight, temperature (day, night and seasonal), moisture (rainfall and humidity) and soils (type, pH and nutrient content).  These factors combine to make what is called the "optimum growing conditions."  Some plants have a wide tolerance in all or some of the requirements, enabling them to be grown over a wide area.  Others are so demanding in their requirements that they are greatly limited in usage.  Customers newly interested in gardening should be encouraged to start with some of the more adaptable plants.

 

The great challenge in the nursery industry is to provide as wide a variety of plants as possible that can develop to their fullest potential in the situations where they will be used.  The answer to the challenge is partly in understanding the plant's needs and learning to adapt existing conditions to meet these needs.

 

Irrigation can augment natural rainfall, soil amendments and fertilizer can modify the natural soil and both shade cloth or trees can reduce light intensity.  However, increasing light intensity is more difficult.  Selection  of the brightest areas is necessary for plants requiring high light intensity (bright sunshine).

 

In our gardens we will find certain consistent variations in light, temperature and moisture.  We call these different small areas "micro- climates" (little climates).  For example, on the north side of the house, there is more shade, the ground stays cooler and there is less light  intensity.  The south side of the house and the west side of the house have  less shade (barring trees), the ground warms up faster and to a higher  temperature and the light intensity is higher.  The east side is generally  cooler than the south or west, yet warmer than the north.  Trees, structures  and prevailing wind patterns can modify these conditions some­what.  Elevation  may also be a factor as cold air drains to the lower areas at night, possibly  even affecting the survival of some plants that are not sufficiently cold tolerant.  Micro-climates differ from the climatic conditions of the general zone by only a few degrees in temperature, but this may be enough to cause a plant to do well, to merely exist, or to die completely.

 

 

PRUNING

 

Plant growth can be both controlled and modified by proper pruning.  We have already mentioned the possibility of keeping a plant to a desired height by prun­ing.  The most conspicuous example of this is found in formal hedges that are kept to size and shape by regular clipping.  It is important to shape a formal hedge so that the top is narrower than the bottom.  If this is not done, the lower leaves drop due to inadequate light, and the plant is bare and"leggy".  Plants can also be kept to a size, yet remain informal in growth pattern.  Abelia grandiflora  generally grows as a large shrub, which may get  too big for many residential sites.  It can be maintained as a much lower  informal shrub by selectively prun­ing out leaders, beginning when the shrub is  about three and one-half feet high.  These leaders are cut back to below the  height of the surrounding foliage, leaving an attractive plant without visible stubs.

 

Pruning can be used to produce a fuller shrub or tree by encouraging  branching.  Pruning can increase the light entering into the center of the  plant by thin­ning; it can aid in disease prevention by allowing more air passage within; it can reduce or increase flowering or fruiting; shape the  plant formally or informally; rebalance growth after a poor start or after injury and help the plant through periods of stress.  In short, pruning is one  of the best tools we have to aid plants to reach the optimum growth to fulfill our desires for it.  Even if we don't prune, nature will do some of it for us, though not necessarily in a desirable fashion.

 

Gardening is the science, art and fun of learning the various kinds of plants and their growth requirements, then adapting conditions to meet these plant needs.  The nurseryman needs an ever-increasing amount of this knowledge to best serve his customers.  Take some time each day to observe the different plants in the nursery, get to know them and their characteristics throughout the year and read as much about them as possible.

 

For further information, consult any book on general horticulture, plant science or botany.

 

 

 

SUMMARY

 

Competence in technical knowledge of plant growth aids the nurseryman in growing plants and answering customers' questions in language that they most easily understand.

 

In general, all plants are made up of many parts:

 

     -- roots (root system), which anchor the plants, absorb and conduct water and nutrients, and

             may store food.

 

      -- stems, which support the plant parts, conduct water, nutrients and plant food and may store

             food.

 

     -- leaves, which are the site of photosynthesis and transpiration and are also ornamental.

 

     -- flowers (or cones), which may be ornamental and produce fruit and seeds used in

             reproduction.

 

Plants are very diverse in nature, yet are grouped together by function and characteristics that they have in common.

 

Knowledge of plants aides us in choosing the right plants for the right location and in giving the proper care to the established plants.

 

 

 WATER AND WATERING

                                  

Water is one of the most important factors in regulating plant growth.  Water is also one of the most misused commodities.  Cases of underwatering, overwater­ing, wrong method of watering, wrong time of watering and using the wrong type of water easily exceed those of proper watering.  The average individual probably does not realize the number of mistakes that he makes  because of the many fac­tors affecting water and watering of plants. 

 

In order to better understand just what is involved in proper watering, we need to know something about the nature of water and how its use is  affected by the plants being watered, the soil (or media), methods of  application, and in some cases, the nature of the containers used.  Sources of  water include rain, private wells, municipal or commercial water systems (using well water, lake,  reservoir or river sources).  Cost of water usually  depends upon the source and varies considerably from area to area.  However, this economic factor is impor­tant enough, along with the ever-increasing  demand for available water to make use of proper watering procedures  practically mandatory. 

 

With water coming from so many possible sources, its quality varies  con­siderably.  For example, the soluble salt content may vary from practically  none (rainwater) to high soluble salt content.  In some areas where the soluble salt con­tent is not too high, there may exist problems of a single nutrient being too abun­dant.  More often when total soluble salts are high, those nutrient elements that are already present should not be applied as  fertilizer.  Where an element is already at toxic quantities in the water, avoid using more of that element in the fer­tilizer applied and choose plants  more tolerant to the salt.  Acidic water seldom causes any serious problems, but high pH (alkaline) may be a real problem.  Where the soil pH is already  over 7.0, the addition of alkaline water could well be detrimental to plant life.  Watering through a mulch of Canadian peat moss should help alleviate the problem.

 

In some areas of hard water (either alkaline or from some other chemicals), the homeowner often has a water softener.  Water from this type of water sof­tener should never be used to water plants, either indoors or out. These softeners use sodium ions (NA+) to replace the ions that cause the hardness.  Sodium is not a plant nutrient but may enter the plant instead of potassium (essential to plant growth) causing a potassium deficiency in the  plant.  Where softening of the water is the only alternative, the customer should follow the example of the com­mercial plant growers and use a system that uses phosphoric acid as a softener.

 

 

WATER APPLICATION TO LAWNS AND PLANTS IN THE GROUND

 

When water is applied by any means, rain, sprinkler or flood irrigation, only a fraction is actually used by the plants.  The first water lost is due to run-off from the soil surface.  Run-off increases the surface crusting, compaction of the soil as well as increased slope of the land.  Soil compaction and surface crusting can be relieved by the addition of organic matter to the soil and even by surface mulching in extreme cases.  If the slope of the land is too great, water must be applied slowly, or in the case of rain, adequate drainage provided.  Water penetrates the soil and fills up all of the pore spaces (spaces between the soil particles).  The rate of penetration depends upon the type of soil, with penetration in sandy soil much more rapid than in clay soils.  For example, when one inch of water is applied (excluding run-off), sandy soil will be penetrated 12 inches; loam, 6 to 10 inches; and clay, 4 to 6 inches.

 

Some of the water that penetrates the soil continues to move downward due to the force of gravity.  Soil with larger particles (i.e., sandy) has larger pores and, therefore, loses a larger amount of water to gravity.  While this water is theoreti­cally available to the plant, it remains in the soil for such a short time that it is of negligible importance.  Nutrients are also carried down past the plant roots in this water movement.  When all of this gravitational water has been removed, the soil is said to be at field capacity.  The percentage of water remaining in the soil at field capacity, based on dry weight of the soil, ranges from 7 percent for sand, through 15-25 percent for loam, to 35 percent for clay soils.  However, all of this water isn't available to the plant as percentages varying from 3.5 percent for sand to 17.5 percent for clay are held so tightly to the soil particles as to be unavailable to the plant.  Organic matter added to sand both increases the percentage of water at field capacity and the amount of bound water.  The net effect is to increase the amount of water available to the plant.

 

There are two forces that combine to hold the water in the soil, adhesion and cohesion.  Water adheres to the surfaces of the soil particles.  Water also has a high surface tension causing the water droplets to cohere (hold together).  This can be partially demonstrated by spilling a small quantity of  water on a clean pane of glass.  Some of the smaller droplets tend to join together to form larger droplets.  This is cohesion.  If the pane of glass is tilted slightly, a film of water will remain as the rest runs off.  This film is an example of adhesion.  A further demonstration that also shows the effect of pore size is to take several glass tubes of different diameters and place one end in a basin of water.  The water begins to move upward in the tubes, moving highest in the tube with the smallest diameter. 

 

 

WATERING PLANTS IN CONTAINERS

 

Containers vary from those for the smallest house plants to some extremely large outdoor containers designed for trees or large shrubs.  However, they can be classified for watering purposes into two groups; those with drainage and those without it.  It is essential in either case that the plants in the containers be planted in a proper media.  There are very few instances where a native soil is satisfactory.  Normally, organic matter must be added.  The best situation for the container plant is to prepare a media using sand and organic mat­ter (usually peat or ground bark) or loam soil, sand and organic matter.  The medium may vary according to the plants, but should contain from one-third to one-half organic matter by volume (possibly even more for azaleas, camellias and some house plants).  This media is not only better for the growth and support of the plants, but greatly reduces watering problems.

 

Water should be added slowly to the container to avoid splashing and washing out of materials from the surface, the rate somewhat regulated by the size of the container.  Where the container has natural drainage, apply sufficient water so that a small amount comes through the drainage holes. Care should be taken that the soil ball never dries out or it will separate from the surface of the container and the water will simply flow out around the soil ball and through the drainage holes, leaving the interior of the ball dry.  Where the container does not have drainage, a measured amount of water (determined by practice) should be added to the container.  This can be done by timing the flow of water or using a water­ing can with a measured volume. Further protection to prevent "wet feet" of the plants in containers without drainage is provided by placing a small amount of ac­tivated charcoal scattered on the bottom.

The most difficult question of all is "when to water (how often?)".  The only proper answer is "when the plant is dry."  However, extreme care must be taken in answering this question for a customer to not sound facetious.  A good indica­tion of need for watering is the surface drying of the soil from a depth of 1/4 inch to one inch, depending upon the type of plants and root depth.  Another test is to form a hand-full of the soil in question into a ball in the hand.  If it adheres together, there is usually adequate moisture; if it appears more than a "mud pie" there is far too much moisture; and if it completely crumbles, there is insufficient moisture.  By determining where the ball fits in this scale, the time or interval of watering can be determined. With the exception of those plants that grow in water or on the very edge of ponds and lakes, it is generally better that some drying takes place between watering, short of wilting.  So, water less often and water enough to penetrate the soil to a depth of the roots.  This may mean daily (or more often in extreme dry weather) for plants in small containers, at 4 to 8 day intervals for lawns and shallow rooted plants (depending on soil type), and up to monthly intervals for trees and large shrubs.

 

This method of watering is much less important, providing the amount of  water is right and that there is no surface splashing or too great a run-off. However, several methods are available, some of which are time saving and possibly water saving.  Grandmother may have gotten satisfactory results from sprinkling her lawn every night with a hose nozzle; but then grandmother was generally there every night to sprinkle it.  Her grass has extremely short roots (roots only grow well to the depth of water penetration) and had she neglected it for several days, it would have suffered badly and died within a week or two.  Hand sprinkling one inch or more of water on the lawn at one time at the proper rate would exhaust the patience of most of us.  Hand watering is satisfactory for plants in containers and occasionally supplying extra water to a tree or shrub in or near a lawn area where normal lawn watering does not penetrate deep enough.  Even hand watering can be speeded up by using water breakers or bubblers on the end of the hose.  These allow greater volume of water at reduced force.

 

     Much of the watering of individual gardens is done by using movable sprinkler-hose combinations.  With several sizes of hoses and many different sprinklers available, it is imperative that the right combination of hose and sprinkler placement be used.  Hose sizes generally available are 1/2 inch, 5/8 inch and 3/4 inch, with 7/16 inch and 1 inch occasionally on the market. The 7/16 inch is not adequate for most situations and 1 inch is too heavy for most homeowners.  The most satisfactory sizes are 5/8 inch and 3/4 inch, with the 3/4 inch adequate for watering containers (except the larger sizes) or for small sprinklers to catch odd corners.  A customer should be advised to purchase a quality hose for greatest satisfaction.  Cheaper hoses tend to be stiff and difficult to manage in cold weather, tend to kink, crack, split near the ends, and burst when under pressure too long in the hot sun.  The most common types of sprinklers are the rotating impulse sprinklers (rainbird type), oscillating and fixed head sprinklers.  All sprinklers have particular spray patterns, most of which re­quire overlapping to provide the proper amount of water evenly distributed over the entire area.  A good method of checking evenness of watering is to secure a number of straight sided cans of equal diameter (coffee cans are good), space them evenly throughout the area and water the whole area using your normal placement.  The result should be the proper depth of water in the can with the shallowest level and with no more than a slight deviation between the can with the shallowest level and that with the greatest amount of water.  If any area is receiving inadequate water or if the distribution is too uneven, the pattern of sprinkler placement and/or type should be changed.

 

Permanent sprinkler systems, with either manually operated valves or under automatic controls, take much of the guesswork out of sprinkler setting when properly designed.  They also save labor and eliminate hose marks in the lawn as well as unsightly coils of hoses lying around.  They are available in black plastic, PVC and galvanized pipe, with either impulse type, rotating or fixed head sprinklers.  However, except for the simpler installations, and unless the customer is experienced, they should be designed and generally installed by experts.  If your nursery provides a sprinkler designing and/or installation service, direct your cus­tomer to that department.  If not, determine your nursery's policy of referral.  Do not attempt to design a system for the customer yourself if you are not ex­perienced in this field, nor encourage your customer to proceed without adequate assistance unless he has had experience.  For those systems the customer can in­stall himself, the coffee can method of checking results in a good policy to insure proper coverage. 

 

For further information on watering, the reader is referred to:  Sunset Basic Gardening Illustrated, pages 45-50; Sunset Western Garden Book, pages 44-48; reference manuals produced by Irrigation Technical Services of Lafayette, Califor­nia.

SUMMARY 

 

Water is one of the most important factors in plant growth.  Yet water is probably one of the most misused commodities and proper watering is one of the most difficult concepts to convey to the consumers.

 

There are many more cases of improper watering (too little, too much, wrong methods, wrong timing, etc.) than of watering properly.

 

All plants need a certain quantity of water for proper growth functions. The amount of water applied to supplement natural rainfall, and the frequency of ap­plication, must take into account the factors of plant growth, transpiration, run-off, and the water-holding capacity of the soil.  Plants in containers, especially those containers without a natural drainage, need additional special care in water­ing.

 

Methods of watering vary greatly, from hand watering with hose or watering can, use of portable sprinklers and garden hose, to permanent sprinkler systems.  Adequate coverage and proper timing are more important than the method used.

 

While permanent systems generally are best, they should be designed by experts.

 

 

SOILS

 

What is soil?  Good soil is a living, breathing, complex moisture of minerals, organic matter (dead organisms) and living organisms (as many as two billion per cubic inch).  It provides support for plant roots and holds moisture and minerals for plant use.  It has been formed over the centuries by the actions of water, wind, sun (heat), freezing and thawing and by the action of plant life itself.  It varies in thickness from a few inches to many feet. It also varies in texture, struc­ture and mineral composition based on its parent material and the conditions un­der which it was formed.  Rarely is any one soil completely satisfactory for all of the plants available in nurseries.

 

Soil texture:  The relative size of the particles that make up the soil is ex­pressed by the term texture.  It refers to the fineness or coarseness of the soil.  More specifically, texture is the relative proportions of the different soil separates, sand, silt, and clay.  Many physical and chemical reactions in soil are governed by its texture.  This is because texture determines the amount of surface on which the reactions can occur.  Soil particles have been divided into groups en­tirely on the basis of size, without regard to their chemical compositions, color, weight, or other properties. These sizes range from slightly less than 1/8 inch diameter for fine gravel down to clay particles of less than 1/12500 inches.

 


Size and Surface Characteristics of Soil Separates

 

To clarify a relative particle size, imagine that the clay particle is the size of a radish seed.  In comparison, a single silt particle would be the size of a basketball and a coarse sand particle the size of a 7-1/2 foot (diameter) balloon.

 

The presence of the three separates can be determined in a soil sample by rubbing a small amount of moistened soil between the finger tips.  Sand, being granular, has a gritty feeling, silt a slick feeling (like talcum powder) and clay a slippery-sticky feeling.

 

Soils are named on the basis of the separates they contain; i.e., "sandy soils", "clay soils", "clay loams", "silt loams", etc. with the name indicating the predominate particles present.  A proportion so that none of the three was dominant over the other two is a loam.  The term loam is also much misused (i.e., garden loam), so that it is essential to have a firmer basis in discussing soil problems with a customer.  It is best where any doubts exist to have the customer bring in a sample of the soil from his lawn or garden.

 

Soil Structure:  The way that the various particles are arranged within the soil determines the soil structure.  Structural names, i.e., sandy, platy, crumby, blocky, are self descriptive.  Structure is either single grained as in sand soils or in aggregates of smaller particles grouped together as in the clay soils.  Soil struc­ture affects water movement and the handling qualities of soils.

 

Organic Matter:  Soils are classified as either mineral soils or organic soils, according to the percentage of organic matter present in the top 12 inches.  Or­ganic soils are those which have more than 30 percent organic matter (20 percent if the soil is loamy sand or coarser).  Organic soils are further divided into peats and mucks, depending on the degree of decomposition.  In peat, most of the original plant fibers can be recognized; whereas, in mucks, they are decomposed beyond recognition.  Most soils have considerably less than 20 percent organic matter and, in fact, most soils need added organic matter for best plant growth.

 

Organic matter favorably affects soil structure, increasing the water holding capacity of sandy soils and the workability of the clay and other "heavy" soils.   (The terms heavy and light soils, according to common usage, are based on the effort needed to move tillage equipment through the soil, not on the physical weight of the soil itself).

 

The organic matter in the soil is the residue from plant and animal tissue.  The presence of living organisms in the soil is also important, contributing to the better growth of plants.  Some of these organisms cause the decay of dead plant and animal material, releasing nutrients which become available to living plants.  Others fix nitrogen from the air (nitrogen fixing bacteria), attack harmful or­ganisms, burrow tunnels through, improving aeration and releasing minerals (earthworms), and change inorganic (mineral) soil constituents.

 

 

Some of these organisms in the soil are also detrimental to plant life. Fungi cause rots, damping off and other diseases; bacteria cause blights; cutworms eat plants; nematodes damage roots and other plant structures; and some forms of in­sect life in the soil are also detrimental.  Soil in good tilth and properly cared for often contains beneficial organisms that hold the detrimental organisms in check.  However, when the number of detrimental organisms of any type build up to the point where natural controls cannot cope with them, chemicals must be used to bring them back into balance.

 

Soil Reaction:  Refers to the acidity or alkalinity of the soil.  It is expressed in terms of pH, in units on a scale of 0 to 14, with 7.0 neutral, below 7.0 acid (increasingly acid to 0).  For example, a pH of 5.0 is ten times as acid as a pH of 6.0; and above 7.0 alkaline in reaction (alkalinity increases to 14 the same man­ner as acidity increases below 7.0).  The greatest number of plants grown in the Northwest do best in a pH range of 5.5 to 7.0 with some plants such as azaleas, rhododendrons and camellias preferring soil slightly more acid (pH 5.0-6.0).

 

The soil pH is not the factor which controls plant growth.  It is only a good indicator of what nutrients are soluble (available) or insoluble (unavailable), which type of micro-organisms are likely to predominate and what type of chemi­cal reactions to expect.  It is a useful tool when backed by knowledge and ex­perience.  Simple test kits for soil reaction (pH) are readily available and are suffi­ciently accurate when used carefully.  They may well be a useful tool to the  nurs­eryman to help solve a customer's soil problem, so long as other pertinent informa­tion about the soil is also available. 

 

Soil reaction can be modified by addition of certain soil additives and by use of fertilizers.  The addition of lime will make acid soils more alkaline (also wood ashes).  The addition of gypsum or sulfur will make alkaline soils more acid.  Care must be taken to prevent an over-reaction.  It is often advisable to base cor­rective measures on a competent soil test unless previous experience with the soil type in question is adequate.

 

Soils contain varying amounts of natural fertility based largely on the parent material from which they were formed, their texture, and the effects of moisture on them.  Clay soils usually contain more minerals than sandy soils. Clay soils have a much greater surface area than sands.  Minerals are usually held on the sur­face until released to the plants on contact with the plant roots.  The addition of organic matter to a sandy soil increases the surface area and improves the soil's ability to hold minerals.  Even though clay soils contain more minerals than sandy soils, it cannot be assumed that any or all essential nutrients are present or absent in any given soil sample.  Only soil testing by a reputable laboratory can indicate this.  What we can assume is that in adding a chemical fertilizer, it will be im­mediately and totally available in sandy soils, but will also leach out rapidly in suc­cessive waterings.  In clay soils (or sandy soils modified with sufficient organic matter) much of the nutrients will adhere to the surface of the soil particles to be more slowly available to the plant and less subject to leaching or loss.

 

The customer's soil problems:  As we have already noted, soils vary greatly.  Even next door neighbors in the same valley area could have different types of soil, as much of the soil adjacent to rivers had been deposited at various times and in various thicknesses.  It is difficult to determine the nature of a customer's soil from a color or word description. Black soil could equally describe a loam (an ex­cellent soil with almost no problems) to one of the clay soils found in some areas.  If possible, suggest that the customer bring in a sample of his soil when you have any doubts in your mind about making recommendations for plantings, additions, etc.  At least, ask enough pertinent questions to assure that you understand his problems.

 

According to the size of the area in question and to the specific plants that the customer is interested in, we can consider soil treatments and usage in three ways.  The first consideration is those small areas that require special treatment; i.e., planter strips, built-in planter boxes, containers and sections of larger areas that are to be used for plants like azaleas and camellias that have more demanding soil requirements.  The best suggestion for these situations is the complete removal of the soil (to a depth of at least 12 inches) and replacement with a soil mix suitable for the intended plants. For very small areas and planters, planter mixes are usually sold in the nursery.  For larger quantities, a suitable mix can be made based on the original soil plus additives.  Mineral additives include sand, vermiculite, perlite and pumice and become a permanent part of the soil.  Organic additives include peat, ground bark, sawdust, leafmold, manure, etc.  These break down to an end product called humus, and should be added on a regular basis.  A good rule of thumb for a loam soil is the addition of 1 part sand and 1 part peat or ground bark to 2 parts of soil.  Heavier soils would require greater quantities of sand and bark, while sandier soils would only need the organic matter additives. 

 

The second situation would be that of larger areas where the soil has no special problems but needs improvement in water-holding ability and/or increased organic matter.  Generally, organic additives are recommended here, either over the whole area when lawn, ground cover or bedding plants are to be used, or in enlarged holes for the planting of shrubs and trees from containers.  At least 1 inch of ground bark or peat should be added to most "good garden soils" up to a minimum of 25% (3" or organic additive mixed with 9" or "plow depth" of soil) to those soils that are very sandy or have too much compaction or other problems.  For example, a 5.5 cubic foot (compacted) soils that are very sandy or have too much compaction or other problems.  For example, a 5.5 cubic foot (compacted) bale of peat moss equals 11 cu ft. of loose material.  This will cover an area of 131 sq. ft. (10 x 13), one inch deep.  One cubic yard of ground bark will cover an area of 108 sq. ft. (approximately 10 x 11), three inches deep.

 

These additives must be thoroughly mixed with the soil.  The greatest problem in planting canned stock is the transition layer between the soil ball in the con­tainer and the native soil surrounding the place where it is planted.  If the shrub or tree is planted into a hole barely large enough to hold the soil ball, there is a good chance of problems occurring.  If the two soils have too great a difference, water may not be able to move from one to another, either creating a situation where the soil ball becomes overly wet while the surrounding soil remains rela­tively dry, or the converse, where the surrounding soil remains moist and the soil ball drys out.  Either situation can cause damage to roots and the failure of the plant to establish itself.  If the native soil is either considerable heavier or more compact than that in the root ball, the plant roots may not be able to penetrate the native soil.  All of these problems can be resolved by establishing a proper transi­tion layer between the soil ball and the native soil.  The hole for the plant is dug at least twice as large and half again as deep as the soil ball.  The native soil removed is mixed, 2 parts native soil to 1 part sand and 1 part peat or ground bark.  This mixture is placed in the bottom of the hole, firmed down to the proper depth and the tree or shrub is placed in the hole.  The same mixture is used to fill the hole being sure to properly tamp and water it in.

 

The most commonly used organic additives are peat moss, ground bark, com­post and miscellaneous organic materials.  Pea