One look at its lush flowers, and you are sure you are going to kill the fragile beauty. But azaleas (Rhododendron or Azalea spp.), while gorgeous, are not garden prima donnas. They grow happily without much intervention in dappled sunlight in U.S. Department of Agriculture plant hardiness zones 4 though 9. Like many other plants in the vast Rhododendron genus, azaleas require well-drained soil and regular irrigation, but you can hold off on fancy fertilizers or soil amendments.
Quarantine new azalea plants for several months before adding them to the azalea garden to protect established plants against a black vine weevil infestation. Watch the leaf margins of the plant for signs of chomping. Larva of the weevils feed on azalea roots and can arrive with a new plant. When adults emerge, they chow down on tender spring azalea leaves and are very difficult to eradicate.
Choose a flower bed with acidic soil in dappled sunlight. Partial shade is the preference of the plant and also encourages the spider population, a natural predator of azalea lace bugs. Spiders shy from plants receiving direct sun, while lace bugs love plants in hot, sunny spots. Azaleas planted in direct sun also suffer from sunburn.
Work 3 inches of organic compost into the soil before planting your new azalea in spring or fall. Turn the soil to a depth of 12 inches to accommodate the plant's shallow root system. Dig a hole as deep as the container and twice as wide, and fill it with water to test drainage before transplanting the azalea. Plant the azalea in a raised bed if soil drainage remains poor. Poor drainage can water-log azalea roots and encourage Phytophthora rot.
Water azaleas early and often after transplant, providing 1 inch of water on a weekly basis or 1/2 inch twice a week for the entire first year. Do not allow the plant's roots to dry completely at any point, since dry roots can kill a new azalea. Avoid overhead watering because plant humidity encourages Botrytis blight.
Mulch your azaleas with a 3-inch layer of shredded leaves, leaf mold, pine needles or pine bark mulch. Do not use materials that raise the soil's pH, such as shredded hardwood. Spread the mulch around the plant bed, but keep it at least 3 inches from foliage to discourage meadow mice who like to live in the mulch and snack on azalea bark and roots.
Avoid fertilizing. Most azaleas thrive without fertilizer if you work in organic material before planting and use organic mulch. Too many nutrients in the soil encourage insect pests like lace bugs and azalea whiteflies.
Prune azaleas for health, not just to size the plant. Trim the plants after they finish flowering to remove branches with fungal cankers. Identify cankered branches in late summer by looking for wilting or dead foliage. Remove the diseased branches during dry weather, cutting back at least 6 inches into clean white wood. Burn or dispose of the trimmings to prevent fungal diseases from spreading.
- For extra-long flowering, gardeners in USDA zones 7 though 9 can grow wild cherry azalea (Azalea "Nuccio's Wild Cherry"), a dwarf plant that stays under 4 feet tall and produces bright flowers. If you life in a warmer zone, try an azalea called "Alaska" (Azalea indica "Alaska") that thrives in USDA zones 9 through 11. It grows to 5 feet high and 6 feet wide, producing snow-white flowers.
- Keep your eye out for azalea pests that cause aesthetic issues but do not endanger the plant's life. One of these is the aphid, a small, pear-shaped bug with a long antenna. Cultural controls work best for this common garden bug, including cutting down nearby weeds that might house the aphids and encouraging their natural predators like parasitic wasps and lady beetles. Knocking aphids from the azalea with hose water often is enough.
- If you see pests like caterpillars eating azalea leaves, brush them off into soapy water, then prune off the damaged foliage.
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