In nature as well as in gardens, shade is never a constant: it depends on a fluctuating framework of trees and shrubs and#8212; the bones of the garden. This shade-giving framework changes steadily and thus alters the location, timing, and intensity of the shade it provides. In time, gardeners may have too much shade. The remedies are simple. The most obvious and frequent solution is to cut down trees or tall shrubs or to resort to "limbing up" the offending trees. Some trees and most tall shrubs need periodic pruning for best performance anyway, so this pruning can be performed with ultimate shade requisites in mind. As trees and shrubs grow older, eventually they die and must be removed or storms topple them. Gardeners should be aware that their shade might disappear in spots. With the passing of time, all gardens change.
For gardens without shade-giving trees, shade may be created by erecting shade houses or vine-covered pergolas. These can be rudimentary structures or they can take on a more architectural tone. As decorative, functional, and useful as they may be, these structures can never replace the living beauty of shade-giving trees and shrubs in a woodland garden.
The wild woodland floor is made up of the byproducts of tree growth and organic life in the woods. Such woodland soil is to die for but rarely, if ever, is such "gardenerand#39;s gold" available. In many residential areas, the suburban landscape is so thoroughly disturbed that gardeners must "create" their own soil.
To take available soil and improve it to attain good physical structure and openness (a condition sometimes referred to as good tilth) is timeconsuming, labor-intensive, and often expensive. Adding organic matter to natural clay or sandy soils is essential. Among the types of organic matter suitable for gardens are ground bark, coarse sphagnum peat, or ground natural waste, such as peanut hulls or corncobs. Ground tree clippings can be obtained cheaply and are sometimes free for the taking. Gardeners can collect pine needles, leaves, or other natural waste; once composted, these materials make fine soil amendments. There is nothing better than adding humus from a gardenerand#39;s compost pile.
Knowing the soil is essential to making a garden. Many county extension offices of the United States Department of Agriculture (USDA) provide a soil analysis service either free or for a nominal charge. Soils can be acid, alkaline, or neutral, which level is indicated by the pH number. Neutral soil is represented by pH 7. Readings above 7 indicate increasingly alkaline conditions, and those below 7 indicate increasingly acid conditions. Inexpensive pH meters are available at nurseries, so gardeners can do their own pH testing.
Many shade perennials with large leaves require considerable available and constant amounts of water in the soil. These conditions can be accomplished by adding organic matter to the soil. Some soils can hold too much water. Slow-draining clay soil, for example, must be "opened up," also by adding organic matter. Few shade perennials survive in stagnant soils. Soils must be able to breathe. Good garden soils have a high percentage of open space, called pore space, usually occupied by air and water and#8212; the best have around 50 percent solid matter and 50 percent pore space. In fine clay soils the pore spaces become very small, but surface tension increases, so the soil can hold large amounts of water. Clay soils have poor percolation and thus are usually sticky and wet. Again, adding liberal amounts of coarse, organic matter improves the soil.
Agricultural topsoil is composed of 90 percent mineral and 10 percent organic matter. Old, undisturbed woodland soil, by contrast, can have as much as 50 percent organic matter. A high volume of organic matter is preferred in soil for the shady natural garden. Although organic content is important, some mineral content should be included for balance by mixing in natural, mineral-rich topsoil.
Many cultivated shade perennials, except some wildflowers, are relatively heavy feeders. The best fertilizers are slow-release types like Osmocote Plus. The 18and#8211;6and#8211;12 formula, with six monthsand#39; time release, is ideal for shade gardens. Chemical fertilizers, such as ammonium nitrate or superphosphate, are not recommended.
Making soil does not mean replacing existing topsoil but adding organic matter to the cultivated surface layer of soil. It is important to get the soil analyzed to determine the amount of organic matter required. It is not enough to "make" or improve soil, but it must be maintained in good tilth. From time to time it will be essential to "smell" and "feel" the soil and to have it retested. The soil of shady gardens under pines and oaks can become more acid in time, and it is prudent to test the acidity now and then.
Trees are usually the shade-giving "roof" of a garden, but they can bring trouble and#8212; namely, damage to the underlying plants. Physical damage is common: trees bombard the garden below with large cones, nuts, pine needles, and other cast-offs. Tree droppings, such as the resinous droplets that descend from many pines or the sticky nectar exuded by some flowering trees, turn black in short order by way of fungal action.
Shade trees stretch their feeder roots over large areas. They feed greedily on the splendidly friable, fertile soil provided in the planting areas and can eventually stunt the shade perennials grown there. Check for invading tree roots at regular dividing time. If root invasion has occurred, remove the roots, screen the soil, and replant everything. This is a good time to divide plants for increase. Landscape fabric in the bottom of the beds sometimes delays the inevitable bed restoration.
Viruses that mottle the blossoms of tulips are considered beneficial. Others, however, cause chlorosis (yellowing of the leaves), "bad" mottling or mosaicism (white or yellowish spots), blotching (whitened areas larger than spots), wilting and collapse of plant tissue, leaf curl, mosaic and ring spots, general reduction in vigor, and stunting. Viruses are spread by cutting or sucking insects that carry cell sap from one plant to another, as do gardeners who use the same garden tools first on infected and then on healthy plants. Usually, a visit to the county USDA extension office or a universityand#39;s plant pathology department can help identify viral diseases and seek countermeasures.
Bad bacteria and fungi generally enter plant tissue that is cut, torn, or abraded, and once inside the plant tissue, multiply rapidly. They can cause decay, contribute to secondary infections, and may kill the plant. Treatment comes often too late, because bacterial and fungal diseases, such as crown rot, start hidden in late autumn and the destructive action continues below ground until spring. By the time the plants are expected to produce their spring flush of leaves, the rootstock may have turned to mush.
Early detection of symptoms is essential. That is why good gardeners spend a lot of time in their personal landscape visiting the plantings and checking everything: they try to detect problems before they become disasters. Some gardeners exclude all plants and any other materials brought in from outside in a "quarantine area."
During the growing season, bacterial and fungal diseases are easily spotted and gardeners should become familiar with their symptoms. Examples of these maladies are leaf spot, anthracnose, crown gall, mildews, rusts, smut, cankers, black spot, and some blights. A visit to a county USDA extension office is particularly valuable, because some pathogens concentrate in certain regions of the country, and these offices are aware of such infections and can recommend countermeasures. Whatever treatment options are used, they should respect our environment.