IN THE GARDEN MYSTERY OF THE DYING AZALEAS.
Q: Suddenly our azaleas are dying. Some are newer plants, replacements of ones that died; others have been established for some time. The dying plants are not confined to just one area of the garden, which makes it even more puzzling. Some are shade plants, others are in sunnier locations, some are in containers. They were fertilized with all-purpose plant food. We have older, established plants that are still healthy but wonder why this rather sudden onset with so many of our azaleas.
A: Azaleas are among the most challenging plants to grow in the Valley, yet they remain our most popular flowering shrub for shade gardens. The main reason for our difficulty with azaleas is that the environment we ask them to inhabit is the opposite of what they call home.
Azaleas are native to the acid soils of east Asia, but our soil is alkaline; the habitat of azaleas is rainy, while ours is dry; azaleas are often found growing wild on wooded slopes with excellent drainage and a thick layer of leaf mulch all around, yet we put azaleas on flat ground and, with leaf blowers, scare off every leaf that dares to land in their vicinity.
You are not alone in having problems with azaleas. Azaleas planted in our part of the world tend to be short-lived. The biggest problem in growing them is the soil-borne phytophthora fungus. If you see individual shoots of an azalea suddenly wither, you should suspect that the culprit is phytophthora.
When you say some of your dying azaleas are recently planted replacements, I suspect phytophthora because of its persistence in the soil. The only way to combat phytophthora is to apply a fungicide to the soil. However, you may have to hire an ornamental pest control company to do the job since the chemicals required are probably not available to the general public.
It could also be, however, that you overfertilized, since you say that all your azaleas, including those in containers, appear to be dying. Look at the three numbers on the bag of fertilizer that you used. The three numbers on the bag, separated by dashes, represent the percentages of nitrogen, potassium and phosphorus in the fertilizer product. 6-10-4, for example, means 6 percent nitrogen, 10 percent phosphorus and 4 percent potassium are present.
If any of these numbers is greater than 10, this could explain your problem. Azaleas are sensitive to strong, or even medium-strength, fertilizer formulations. They are killed outright by aluminum sulfate, a fertilizer recommended for hydrangeas. Once azaleas have established themselves, they should not require fertilization as long as they are mulched with leaf mold, ground bark or wood shavings from oak, pine or cedar.
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|Publication:||Daily News (Los Angeles, CA)|
|Date:||Aug 14, 2004|
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