Shrubs

Shrubbery should be planted in a level bed, free of grass, weeds, sticks, roots and large stones. Soil should be soft and rich in nutrients. Soil analysis will determine the type of soil to be used, and the amount of fertilizer, limestone and organic matter needed to bring the soil to an optimum level. (For more information on soil amendment, see “Site preparation.”) Raising the bed will improve drainage.

Once the bed is cleared and the soil is balanced, the arborist should further prepare the soil according to the following guidelines: * Using a spade or rototiller, mix a 4-inch layer of compost and/or shredded peat into the top 12 inches of the garden loam. The compost can be sludge, mushroom compost, well-decomposed leaf mold, grass compost or peat moss. * If sand or additional compost is necessary to amend the soil, it should be added, and the entire planting area should be tilled again. A generous mix of organic material will not only improve the soil structure but also will improve the soil’s binding ability. * Add a 50 percent organic fertilizer at a rate of 1 pound per 10,000 square feet. Because fertilizer works best when the pH level is 5.5 to 6.8, adjust the lime or sulfur content to attain that level. * If there are lumps in the soil, let the bed dry out, and till it again.

The importance of tilling the soil cannot be emphasized enough. Tilling can be done with a plow, a rototiller or hand tools. If hand tools are preferred, a shovel or spade should be used for the first tilling, and a spading fork should be used subsequently to keep the soil loose.

The National Arboretum’s Plant Hardiness Zone map and Hardiness Ratings can be used to assist arborists in shrubbery selection. Like trees, shrubbery should be spaced according to the plant’s spread at maturity. For example, a shrub that will grow to be 4 feet wide should be planted in the center of a space with a 4-foot diameter.

Shrubbery should be planted in the spring, from the time the soil is dry enough to be worked until late May (or even until July if irrigation is available). The outdoor temperature should be at least 50 degrees Fahrenheit. Planting can resume in the fall, after the summer heat passes, and it can continue as long as the temperature remains above 50 degrees. (Note: planting later than that will not give the roots time to grow into the soil, and the plants will heave during frosts.)

Prior to setting the plants, the arborist should remove all sucker growth, as well as dead, damaged or weak branches and roots. The shrubbery can then be planted in the same manner that trees are planted (see “Selection and planting.”)

The shrubbery should be watered immediately after planting, then two more times within the first 24 hours. For the next two weeks, the plants should be watered every two days.

Watering
Shrubbery should be watered deeply, once a week — by rain or irrigation — until the end of the growing season. Workers should be careful to water the soil, as opposed to the leaves, and may find that a soaker hose is the best tool for accomplishing that.

Mulching
A fine-textured mulch — e.g., shredded bark, buckwheat hulls — is used commonly in flower beds, while coarse mulch — e.g., corn cobs, wood chips — often is used with trees and shrubbery. Plastic should never be used as mulch or in combination with mulch. The plastic limits soil oxygen and moisture, forcing roots to surface in search of those necessities. Mulch should be applied to a settled depth of 3 inches when the shrubbery is planted, and it should be maintained at that depth.

Controlling pests
The best way to control pests is to use pest-resistant plants. Many of the cultivars introduced in the last few years are disease- and pest-resistant, as well as drought-tolerant.

In fact, more and more cities are turning to integrated pest management (IPM), which focuses on biology rather than chemicals as an approach to pest control. The IPM strategy is based on the concept that proper site preparation, plant selection, planting and maintenance produces healthy plants with substantial natural defense systems. The plants can tolerate low levels of pests and create a habitat for disease-fighting organisms. The IPM approach to pest control minimizes the use of pesticides and reduces the risk of chemical exposure for workers.

Pruning
Shrubbery requires pruning to rejuvenate and shape the plant. The plant can be pruned by: * trimming branches annually. As with trees, branches can be removed at the crotches of larger branches. * cutting stems annually. Remove one-third of the plant’s stems, cutting them 6 inches above the ground. After three years of such treatment, the plant will be completely rejuvenated; arborists can let the plant grow uninterrupted for several years before cutting the stems again.

When shrubbery is balled and burlapped, only 4 to 5 percent of the root system survives transplanting. Therefore, rapid top growth should not be expected for at least a year after planting, when the roots have re-established. Excessive pruning during that time is harmful, since it inhibits the plant’s ability to generate food in its leaves. Therefore, balled and burlapped plants should not be pruned at all during the first year and only as necessary thereafter. If pruning is required, it should be done after flowering.