Follow these guidelines to grow happy, healthy shrubs
Depending on the plant, shrubs are sold in containers, bare-root, or balled-and-burlapped.
Watering and fertilizing
The water and fertilizer needs of shrubs vary widely, so it's important to learn each plant's requirements before purchase. You'll find that some need littlewater once established, while others require regular moisture throughout the growing season. Likewise, many shrubs need little fertilizer when mature, but they grow better in the long run if given a complete fertilizer each spring during their younger years. A few shrubs, especially those that prefer constantly moist, rich soil, do best with annual feeding throughout their lifetimes. For information on specific shrubs, consult Sunset's National Garden Book or a local nursery.
When you do fertilize, you'll find that controlled-release granular products offer an efficient way to do the job, providing sufficient nutrients to last for an entire growing season. Apply the fertilizer beneath the shrub, spreading it in a wide circle (as directed below); then work it into the top few inches of soil. If the shrubs have extensive surface root systems (rhododendron and camellia, for example), don't cultivate the soil beneath the plants deeply; to avoid disturbing roots, just barely scratch the fertilizer in.
When you apply fertilizer and water, keep in mind that many shrubs have surprisingly extensive root systems. Gardeners frequently treat an area only as wide as the shrub's above-ground spread, but roots often reach much farther than that. As a general rule, water and fertilize in a circle two to three times wider than the plant's diameter at ground level, wider still for tall, narrow shrubs.
To conserve moisture and discourage weeds, apply a mulch around and between shrubs. If you fertilize in spring, mulch after fertilizing. If you need to fertilize later in the season, use a liquid type that will soak through the mulch or a foliar spray.
Managing pests and diseases
Though it's easy to forget those sturdy, uncomplaining shrubs at the back of the garden, it's important to check all shrubs periodically for signs of pests and diseases. Regularly rinse dust and debris from plants with strong blasts of water from a hose; you'll get rid of pests and disease spores at the same time. Periodic hosing also helps prevent the dry, dusty conditions that encourage summertime pests such as spider mites.
The leaves that fall naturally from shrubs may decompose and add humus to the soil. But some leaves drop because they're diseased ― those afflicted with black spot, for example. Unless you're certain that natural debris is disease free, rake it up in the fall and discard it in the trash (don't compost it).