ADAPTABILITY TO SITE

Landscape plants need specific environments for best growth. When choosing a landscape plant, be sure to consider three questions: Will the plant survive the winter conditions in your area? Will the plant grow in the kind of soil and the soil conditions you have? Will the plant need sun or shade?
 
 

Climate zones

 

The U.S. Department of Agriculture (USDA) has studied the climates of all areas in the United states and put them in numbered categories based primarily on minimum low temperatures. Other climate categorization systems have been developed, but the USDA system is used in this bulletin (see map below). An ornamental landscape plant will be hardy in the zone for which it is rated and any zones of a higher number. Remember your zone--some plants may be especially well suited for your zone, and other plants will not grow well there. Cold can kill a plant or cause repeated dieback and gradual decline of a marginally hardy plant. If you wish to grow a tender or marginally hardy plant, you should select a sheltered site or provide winter protection.

 
 
 
 

Soils

 

Many landscape plants need specific soil conditions for healthy growth. Most shrubs and trees grow best in moist, well-drained soils. It is very important that you know what soil conditions exist on your site and how well the soil drains. Poorly drained and soggy soils are not ideal for most landscape plants. With careful plant selection or soil modifications, however, even these sites can be successfully landscaped.

Though landscape plants grow best in moist soil, they do not tolerate having their roots too wet for extended periods. When soil remains too wet for several days or weeks, roots begin to rot. Root rotting causes limp foliage that turns yellow, excessive leaf drop, and stem dieback.

If the soil is poorly drained or a clay type, you may need to modify the planting bed. Mound up planting beds by adding and incorporating 6 inches of a well-drained organic mixture. A mixture of sphagnum peat moss, aged bark, and sandy loam topsoil (1:1:1 by volume) that has a pH reading of 5.5 or 6.5 (acid) will improve drainage, aeration, and nutrient availability for the roots.
 
 

Light requirements

Ornamental landscape plants need light to grow, but some plants require full sun all day while others tolerate some shade. Still others may require a shady area of filtered light to grow best. It is important for you to know the light conditions of the various areas of your landscape so you can choose plants that will grow well under those conditions. It is very frustrating to choose the wrong plant and watch the leaves scorch because the sun was too bright and hot or the branches become weak and foliage spindly because the shade was too heavy.

PLANT QUALITY AND HANDLING

Regardless of how the plants are displayed and packaged at your local garden center or retail nursery, you should always look for good quality plants. First, you should look for species that are not problem-prone. Look for good foliage color and strong branches. Avoid plants that are root-bound in containers. A root-bound plant has a root system that has become too large for the container. You can see the roots growing out of the container's drainage hole. Be sure bare roots of deciduous plants have been adequately protected from moisture loss and bud break has not yet occurred. The soil ball of balled-and-burlapped plants should remain firm, rounded, and intact when handled. Fairly new burlap cloth should hold the root ball. Avoid plants with root balls that are soft, saggy, pancake-shaped, or too small. Plant grades and sizes should be in accordance with the American Standard for Nursery Stock, published by the American Association of Nurserymen.
 
 

Preplanting injury

When a recently transplanted shrub or tree fails to grow and the cause cannot be associated with drought, excessive moisture, or insufficient roots, the plant may have been injured before planting. It may have dehydrated while in storage or in transit, or it may have been subjected to excessively high temperatures.
 
 

Insufficient root system

Recently transplanted plants may not have root systems large enough to support their shoot growth. Therefore, it is a good idea to prune transplanted shrubs and trees to help reduce water loss during the establishment period. When pruning, do not head back the ends of the branch tips; rather, thin out undesirable stems and help maintain the tree or shrub's natural form.

Sometimes trees are dug with inadequate root systems. Do not accept such plants for planting. Industry standards have been established to assist in determining proper root ball diameter.
 
 

Transplanting and planting

Did the plant die after you planted it? Be sure to protect the roots before planting, set the plant at the proper depth, use a good planting soil, firm the soil around the roots, keep the ground moist, and mulch around the plant.
 
 

Juvenility and rootstock suckering

Woody perennial plants grown from seed will not bloom during their juvenile stage of growth, which for some species may be 8 to 10 years. Plants grown from cuttings or grafted plants will flower more readily than seedlings. Frequently, grafted plants will produce vegetative growth below the graft. This rootstock suckering is usually vigorous, juvenile growth that will not produce flowers or possess the desirable ornamental traits of the grafted cultivar. Remove these suckers in the spring when the growth is soft, succulent, and easily removed.
 
 

Graft incompatibility

Delayed graft incompatibility, although not a girdling action, is somewhat similar in end results. The union of some grafted or budded plants fails to function and the plants die. Very often this is preceded by a mass floral display.

IMPROPER PLANT MANAGEMENT PRACTICES

Cultural practices required to care for landscape plants--pruning, fertilizing, watering, and protecting plants. Proper planting and care maximizes growth of landscape plants and keeps them healthy. Improper cultural practices or lack of care can retard growth or weaken the plant's ability to withstand adverse environmental conditions or pest attacks.

Improper cultural practices can even enhance disease development. Watering plants lightly through overhead sprinkling in the evening or at night, for example, can create wet foliage conditions that favor leaf diseases. Allowing plants to get too dry may predispose them to cankers. Blue spruce, for example, usually does not show wilting or other symptoms of drought stress, but drought conditions will increase the possibility of infection by Cytospora canker.
 
 

Pruning at the wrong time

The least desirable time to prune is immediately after the new growth has developed in the spring. At that time, much of the food stored in the roots and stems has been used to develop new growth, and the new foliage should replace this food before you prune and remove the foliage. Otherwise, considerable dwarfing, dieback, and decline of the plant may occur.

It is also advisable to limit late summer pruning, which stimulates new growth on some plants. This growth may not have sufficient time to harden off before cold weather arrives and so may be damaged or killed by low temperatures. Late pruning also removes valuable food reserves.

Prune when twigs, branches, and limbs are dry and when the weather forecast calls for dry weather for a week. This is most important in fall and spring, when diseases are active and easily transmitted to vulnerable plants. Whenever possible, avoid pruning the tender spring flush of growth to avoid tearing new bark tissue and opening wound sites for disease organisms to enter.

Spring flowering trees and shrubs should be pruned shortly after flowering to avoid removing flower buds, which form in late summer on mature wood and overwinter. Prune plants that bloom after the end of June in late winter before new growth starts. These plants develop their flower buds during the spring growth period.

Bleeding of pruning wounds can be heavy on certain trees, such as birch, dogwood, sugar maple, and elm. Minimize bleeding of susceptible trees by making small cuts--less than 3 inches in diameter--and pruning in summer. Bleeding is very likely if severe pruning is done just before growth begins in the spring. Bleeding doesn't harm the tree, but if it's heavy and persistent, it may injure the bark below the pruning cut and cause slow callusing of the lower wound.
 
 

Incorrect pruning

Topping (heading back) is, unfortunately, the most common method of reducing tree size. It is more rapid than thinning, but the results are, in most cases, much less desirable. Regrowth is vigorous and upright from the branch stubs. The new branches form a compact head and broomlike terminals, and they may be weakly attached to older branches.

Thinning-out pruning can be used to reduce the height and spread of a tree. Cut branches to lower laterals (drop crotching). Some limbs may be removed completely. A thinned tree retains its natural shape and is less subject to vigorous watersprouts than a headed or topped tree.
 
 

Excess fertilizer

Too much fertilizer can stimulate vegetative growth to the detriment of flower and fruit production. Excess fertilizer is especially damaging during dry weather. As the soil water decreases by evaporation and plant use for transpiration, fertilizer salts can become more concentrated in the soil around the roots. Plants exposed to these conditions will dehydrate. How quickly dehydration occurs will depend on the concentration of fertilizer salts.

Always follow instructions when using fertilizer on plants, and water ornamental plantings during dry weather. If you apply too much fertilizer, you may be able to leach it out of the root zone by applying liberal quantities of water to the soil. You can confirm soluble salt problems by using a Solu-bridge to make a conductivity test on a sample of soil.
 
 

Lack of water

All plants require some water, and most plants require large quantities if they are to grow normally. Though most plants receive adequate moisture from rainfall or irrigation, plants sometimes become dehydrated, particularly after transplanting or when growing in containers or in adverse sites in a landscape, such as under building overhangs. After transplanting, water plants periodically the first growing season and possibly the second. Water plants in containers and adverse sites regularly to assure adequate water for growth. Be sure to remove burlap--especially plastic burlap, which is commonly used to wrap root balls--from the sides of the root ball and lay it in the bottom of the planting hole at planting time. Attempts to remove the burlap completely may destroy the root ball and damage the root system. Drought-stressed plants are unable to take up nutrients for proper growth. They are also more susceptible to diseases or insects.
 
 

Excess water

Too much water around the roots of most plants used in the landscape can cause them to decline and ultimately to die. Plants with waterlogged roots often contract root rotting diseases. Plants require some oxygen in the soil for good growth and development. If planting sites aren't naturally well drained, take steps to drain the site artificially before planting.

Drainage systems must be connected to free-flowing drains to be effective. Often plants are placed in shallow depressions hallowed out of heavy clay soil. Under these conditions, little or no drainage is possible even if you place rocks or gravel in the bottom of the planting holes. Do not cover the soil surface of planting sites with plastic if the soil is clay or clay foam and is subject to excess rainfall, runoff water, or irrigation.
 
 

Girdling

Plants may decline in vigor because of girdling by a wire of nylon rope encircling the stem, girdling roots or vines, or damage by animals.

Nondeteriorating ropes used to secure the ball of soil during transplanting and guy wires that supported newly planted trees should be removed when they're no longer needed. At planting, be sure to distribute the roots properly in the planting hole. For plants that were produced in containers, this means making sure that no encircling roots are left to girdle the stem as the plant grows.

Most rodent, rabbit, and deer damage is done during winter months when natural food supplies are short. Animal damage can be reduced by the careful use of poison baits, repellents, weed control, wire mesh or sheet metal rodent guards, and high fences to block deer crossings.

Many homeowner activities can also girdle valuable plants. The use of riding lawnmowers has increased the incidence of "lawnmower blight," or physical injury to plant trunks and stems. Mechanical edgers and cultivators often injure young plants by girdling stems.

Delayed graft incompatibility, though not a girdling action, has somewhat similar end results. If the union of some grafted or budded plants fails to function, the plants die. Very often this is preceded by a massive floral display or early fall color. There is no practical corrective actions--plants must be replaced.
 
 

Overmulching

The roots of plants need oxygen at all times. Overmulching kills the roots of shallow-rooted plants by suffocation.

Symptoms of too much mulch include chlorotic foliage--yellow leaves with green veins--abnormally small leaves, poor growth, and dieback of older branches. Disease organisms that thrive under conditions of low oxygen can become active and attack the roots. Sometimes the old root system will be rotted as the plant tries to send out new roots into the mulch layer.

Excessive amounts of mulch applied around tree trunks can lead to cankers on susceptible species.
 
 

Insecticide/fungicide injury

Applying the wrong chemical or improperly applying a pesticide can injure plants. The most common form of pesticide injury is leaf burn, particularly on the margins or tips of the leaves. The propellant in aerosol sprays or the emulsifying agent in emulsifiable concentrates can be responsible for injury to some plants. Dormant oils applied at the wrong time of the year or to sensitive species can also injure plants. Sulfur applied during hot weather may burn the foliage.
 
 

Herbicide injury

If the new growth of plants is malformed and the leaves cupped and chlorotic (yellow or white), it is possible and highly probable that a weed killer, such as 2,4-D or dicamba, has been applied nearby.

Some weed-and-feed lawn fertilizers contain dicamba, an excellent weed killer that should not be applied above the root zone of valuable trees and shrubs. Spray application of 2,4-D-type weed killers should be made only on calm days because certain formulations may drift onto valuable plants and cause various malformations of growth.

Nonselective herbicides should be used with caution because they may wash into areas where they could kill valuable landscape plants. Spray equipment used to apply weed killers should not be used for other lawn and garden chemicals. The improper use of weed killers damages or kills many plants each year. Read the pesticide label! Instruct others to do likewise and to follow the instructions.