Sooner or later, almost every Texan tries to grow azaleas. Azaleas are best suited for an informal garden that has partial shade. This can be a woodland area that receives filtered sunlight through deciduous trees (oaks and hickories) or through pine trees. In fact, azaleas do exceptionally well when planted in groups or masses in an area with a pine canopy. Azaleas grow well at the edge of heavily wooded areas or in partial shade such as that found on the north side of a house or hedge planting.
The time for azaleas to put on their show is February through March. But there are varieties such as Encore, that can bloom two or three other times throughout the year.
Make sure your azaleas get adequate water during their growing season. They need the equivalent of an inch of rain every 7-10 days. However, do not allow your azaleas roots to sit in wet soil. To help conserve moisture, put a nice layer of mulch over the soil around your azaleas.
Azaleas do best in acidic soil. To help maintain an acid soil, add liberal amounts of pine needles, leaf mulch, old sawdust or compost to the soil.
It’s important to have a pH meter when growing acid-loving plants like azaleas in the Houston area. The pH needs to be close to 6.0 on the meter.
Azaleas Care Schedule
Here are the basics for Azalea Care in Houston: (This schedule also works for gardenias, camellias and hydrangeas ... just remember they all have different blooming seasons — azaleas: March/April; gardenia: June/July; camellias: February/March; hydrangeas: May/June) Also remember that even if you have "repeat-bloomers" such as Encore, you still need to follow the care schedule below following the spring bloom cycle.
- Always feed immediately after blooming cycle.
- Feed again 6 weeks later.
- Feed again 6 weeks later, but this time with Systemic Azalea food with Disyston.
- Use any number of Azalea/Gardenia/Camellia Foods on market
- Test pH at least three times per year.
- Keep acidity of acid-loving plants close to 6.0 (6.5 to 5.6 is the range).
- Trim immediately after blooming season.
- Try to trim no more than 1/3 of entire plant.
Some Common Azalea Diseases and Pests:
Petal blight
Flowers become spotted, water soaked, limp, and are quickly destroyed. Dead flowers cling to plants instead of falling to ground. The disease is more severe in cool, moist springs.
Remove old mulch and replace with new in early spring. Drench soil area under plants with Terracolor in January. Spray with Thylate or Benomyl when blooms begin to open. Continue at 7- to 10-day intervals during bloom period. Good coverage is essential. Bayleton may be used once when buds show color.
Leaf gall
Pale green or whitish fleshy galls; leaves curled or deformed. Leaf gall development is also favored by cool, moist weather.
Handpick and destroy affected leaves. Spray with Bayleton, Ferbam, Captan, or a fixed copper fungicide. Start spraying at end of bloom period and continue at 2- to 3-week intervals until mid-June.
Leaf spots
Brown or bronzed leaves, with tiny black fruiting bodies on the dead tissues. Irregular and colored spots on leaf.
Use Maneb, or Bayleton beginning at end of bloom period. Continue at 2-week intervals through growing season or as long as young leaves are present. Refer to Bayleton label for application intervals.
Nematodes
Leaves turn yellow and plants are stunted. They do not respond favorably to water and fertilizer applications.
No chemical control available. Other conditions mimic nematode injury; collect a soil sample from root zone for nematode analysis. Check with your county Extension agent for details.
Winter injury
Entire branches turn brown and die during the growing season. Look for evidence of bark splitting near base of limbs or at ground.
Use recommended varieties. Keep plants in good thrifty condition. Water regularly during late summer and fall.
Iron chlorosis
Leaves turn light green to yellow, then creamy white between the veins; but veins remain green. Usually caused by soil pH being too high, making iron unavailable to plants.
Soil pH may be lowered by adding ferrous sulfate, finely ground sulfur, aluminum sulfate, or iron chelate. Spray foliage with iron chelate for temporary effects.
Spider mites
Leaves become yellow-flecked with stippled areas. Fine webs on leaves may be visible with close observation.
Spray underside of leaves with acephate (Orthene) or feed plant Systemic such as Cygon or Disyston. Spray a second application of Orthene again in 7 days to take care of egg hatch.
Azalea lacebug
Upper surface of leaves has a gray, balanced, or coarse-stippled appearance. Underside of leaves becomes discolored by excrement and cast skins.
Spray underside of leaves with malathion, dimethoate, diazinon or acephate. Repeat application every 10 days until control is obtained.
Scale insects
Usually on twigs or branches. Various colors and shapes. Some look like bits of white cotton; others are brownish.
Malathion or acephate can be used as spray during crawler stage. Dimethoate can be used.
Foliage feeders
Leaf destruction.
Spray with Diazinon or acephate.