ble for the plant to take up for use.
The primary symptom your plants are expressing is what is termed chlorosis. This term is derived from the word chlorophyll, the green pigment found in leaves; therefore, the lack of this pigment results in a yellowing of the leaves and a chlorotic effect.
In azaleas we often see two types of chlorosis - one caused by the lack of nitrogen (the nutrient needed in the greatest amount) and one caused by the lack of iron (nutrient needed in small quantities). Nitrogen chlorosis is manifested in a yellowing of the entire leaf, while iron chlorosis shows up as a yellowing of the leaf blade, but the veins within that blade are still green; this is referred to as interveinal chlorosis.
The easy answer is to add more fertilizer, but with it getting late in the growing season, be hesitant to apply a lot of fertilizer to these plants. You can use a liquid fertilizer and apply it directly to the foliage so that it can be absorbed and help correct the problem at the source.
There are several liquid iron products available where you mix one tablespoon per gallon of water and spray on the foliage. Other liquid fertilizers like Miracle Gro or fish emulsion can be used, but I would recommend using it at half-strength; we want to try to correct a nutritional deficiency without forcing an abundance of growth.
Next spring, just after flowering, use a good slow-release fertilizer, preferably an organic one that will provide the necessary nutrients for season-long growth. I really like Holly-tone from Epsoma, which is excellent for acid-loving plants like azaleas.
Lastly, I am afraid that your azaleas have been attacked by a pesky little insect called the azalea lace bug. These tiny insects are found on the underside of the leaf and are very small. They have a needle-like mouth part that pierces the leaf and literally sucks out the chlorophyll, thus yellowing the foliage.
Often we think this is a nutritional problem when actually the insect is causing the damage. If this is the problem, apply a systemic insecticide that goes throughout the plant so that the chemical can get to where the insect is feeding. Doing this now will at least destroy the adults that are still feeding, but next year start earlier with control measures.
Begin by removing all of the old mulch and fallen leaves this fall - the insects overwinter in this material. Next apply a dormant oil spray in January or February to help suffocate any eggs that are dormant and then apply a systemic insecticide in April (a product with acephate or imidacloprid) so that you can control the lace bugs just as they start to feed, thus keeping them from creating the chlorotic condition.
I know this is a lot to digest, but if you can make sure the pH is in the correct range, apply some much-needed organic matter to improve the soil micro-organisms, add a good, slow-release organic fertilizer appropriate for azaleas, and keep the lace bugs from getting established, then those azaleas will come back in line and display a fabulous coat of dark-green leaves to highlight their spectacular flowers.
Things to do:
If summer annuals have grown leggy (impatiens are prone to this), cut them back halfway and fertilize with a liquid feed product.
Prune and fertilize hybrid tea roses to get them ready for a big fall bloom.
Watch out for magic lilies, surprise lilies and spider lilies as the flower spikes jump out of the ground; the lawnmower and string trimmer can be a drag on flowering performance.
Harvey Cotten is the chief horticulturist and vice president at the Huntsville Botanical Garden. Write to firstname.lastname@example.org or c/o The Huntsville Times, P.O. Box 1487, West Station, Huntsville 35807.
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