Shrubs are the workhorses of the landscape. They anchor perennial beds, frame trees, create backgrounds for bright flowers, and provide cover for wildlife. Many shrubs sport fall color or spring blooms as well. Shrubs usually require much less fuss than herbaceous plants, but an application of fertilizer keeps them happy and functional in the garden.
Evaluate the shrubs. Look for signs of disease or soil deficiencies such as yellowing leaves, abnormally small leaves, dying branch tips, or leaves that fall prematurely. If there are signs of disease or issues with the soil or root system, correct the problem before fertilizing. Fertilizers are not cure-alls; they force a plant to put out new growth, which can further weaken a struggling shrub.
Select the fertilizer. Different fertilizers react in different ways with the soil. For instance, an acidic fertilizer such as Miracid addresses alkaline conditions preventing plants from taking up iron, where a standard fertilizer is not as effective. According to the North Carolina Cooperative Extension, a slow-release fertilizer, with balanced nitrogen content rather than high nitrogen, is best for shrubs. Nitrogen encourages fast leaf growth, which is ideal for lawns but not for trees and shrubs; never use a lawn fertilizer on shrubs.
Broadcast the fertilizer over moist soil at the shrub's drip line in early spring. Donnan Landscape Services advises that fertilizing after the end of June will encourage late-season growth that can be injured by early frosts. Also, do not fertilize when the earth around a shrub is dry; the salts will burn the surface roots. Instead, water the soil first, then broadcast the fertilizer. Water the fertilizer in with a deep soaking.
Fertilize with water-soluble mixtures such as Miracle-Gro by adding the granules to water according to the package's directions. Spray the solution directly on the foliage as well as at the root zone, as plants can absorb water-soluble nutrients from leaves. Don't spray on bright, sunny days, however, as the water will evaporate and leave fertilizer to burn tender leaves.