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May is the last month in what is normally considered our "dry season". An average May will provide just over three inches of rain and some will say that it all comes in the latter part of the month... Whenever the small amount of rain arrives, the word to gardeners is that they must continue to be vigilant to assure that plants don’t dry out. With the arrival of June, our watering responsibilities should decrease considerably.
We haven’t written much about fertilizer, what with the advent of the customized hibiscus formula fertilizer the Chapter has obtained in the past several years. We have heard no negative comments about the fertilizer, however we haven’t asked for comments either. We would be surprised if there hasn’t been a period of trial and error as our gardeners become familiar with the time-release feature of the fertilizer. At this point, suffice it to say, as the temperatures rise and the amount of water required to satisfy your plants increases at somewhat the same rate, the timing of fertilizer applications may require adjustment. "Listen" to your plants – they will "talk" to you!
Keep a sharp eye out for insects. With very little rain and very few predators, spider mites can be expected. The first symptoms include a dry look on lower foliage, then gray-green raised "blisters" appear. The inevitable finally occurs and the affected leaves will turn a dull yellow and fall off. Of course the spider mites do not fall off with the leaves (some may of course), but most have traveled to upper leaves to carry on the family tradition. Affected leaf surfaces are likely to exhibit a salt and pepper look on the undersides. As Barry Schlueter, Editor of The Petaloid, describes them, the pepper is mites and the salt is eggs.
There are several insecticides labeled for spider mites which will provide a degree of control. However, we have found that an approach Mr. Schlueter recommended several years ago has considerable merit. It involves giving your plants a daily afternoon bath with a watering wand that directs the spray on the underside of the leaves. The plants love a cool shower on a hot afternoon and the spray will wash off adult mites and dislodge some eggs. The spray will also disrupt the life cycle of whiteflies and most other insect pests.
Some gardeners transplanted from the north don’t appreciate what the appearance of ants on southern plants mean. While some northern plants require the presence of ants to bloom, more than a few ants on some southern plants, including hibiscus, is not a good thing. Southern ants may be farming aphids and scales that munch on your plants while producing "honeydew" or Sooty Mold that provides a feast for the ants. Spreading a granular insecticide labeled for ants around your hibiscus will help control the "farmers". The water spray may help control the aphids and scales, however a systemic insecticide may be required.
Do your plants have a few yellow leaves? The hibiscus you conducted major pruning on in late February/early March probably don’t. Those plants are too busy "filling out" to go through the "shed an old leaf/put on new leaf" cycle. Hibiscus that you didn’t do any major pruning on may have a few yellow leaves – that will drop off. If there are only a relatively few – that’s normal. Leaf replacement will continue, to one degree or another, throughout the fast growth season. Now, let’s ask another question about yellow leaves.
Do you have a hibiscus with all yellow leaves, but the veins are green? That is not normal. Look to applications of iron (Ironite is OK) and manganese a week or two apart until the leaves regain a consistent green color. You may have to search a bit to find manganese, but it is available. (We aren’t talking Epsom salt here – that’s magnesium.) And still another question about yellow leaves.
Do you have a hibiscus with all yellow leaves and the veins are as yellow as the rest of the leaf surface? That, too, is not normal. (Note we indicated that the leaves remained on the plant. They hadn’t dropped off - pretty much "all at once". If the leaves dropped off, that’s an altogether different problem.) If you have that situation, the first question that you should ask yourself is, "when was the last time I fertilized?" The plant probably lacks the major fertilizer element nitrogen.
May is a good month for air-layering. See The Hibiscus Handbook for instructions about air-layering. It’s a good way to get a good sized plant in 6 to 8 weeks. The successful rooting of cuttings is still a good bet this month.
April June
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