In the Garden:
Coastal and Tropical South
August, 2012
Regional Report

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The occasional hole or yellowing leaf is nothing to worry about.

Garden Worries?

August can be hard on plants of all sorts. Some of the symptoms they display are cause for alarm, but many are not. Here are a few you will see and advice on what to do and not do about them.

Take Action
Summer conditions favor the development of many pests that can debilitate plants if left uncontrolled. For example, hot and rainy weather sets the stage for mildew and potentially serious fungus diseases like rust. There is no cure for fungal infections, but you can stall their progress to uninfected tissues with fungicide sprays. To keep the plants growing, you should treat at the first sign of gray or spotted leaves on plants such as zinnia, cucumber, crape myrtle, and hydrangea.

Insects warrant control if their damage stops the processes of flowering, fruiting, or ripening. Wet weather seems to favor caterpillar outbreaks, not all of which metamorphose into beautiful butterflies. To illustrate, hornworms can strip tomato plants clean of leaves almost overnight and swallowtail butterfly caterpillars do the same to parsley. I am on to the hornworms at the first sign of black frass (caterpillar droppings), dusting with the microbial insecticide Bt and plucking the offenders off when I see them. But I grow lots of parsley, so there is plenty for me and my beloved swallowtails, too.

Dry summers sustain thriving populations of spider mites and all sorts of beetles that devour plants as diverse as beans and hibiscus. When you water, spray under leaves in dry weather to disrupt the rascals and use pesticides as sparingly as possible.

Another late summer phenomenon that can seriously deplete a plant's energy is not a pest at all. When flowers appear on coleus, mints, and other herbs, pluck them off right away to return the plant to vegetative, leafy growth. I use the herb blossoms in vinegars and salads.

Relax and Ignore
There are enough real challenges to deal with, so it is nice to know that changes do not always mean trouble. If you see one or two ruined leaves, do not fret -- just pluck them off. If four more appear in a week, consider what might be wrong. Even then, such symptoms can be harmless. When Japanese maple or dogwood begin to change colors in late summer as they would in October and then drop every leaf, simply rake them up. The fungus that caused the problem began in early spring; make a note to use a fungicide on the new growth next year. Likewise, the occasional yellow leaf on a peace lily or gardenia is no cause for alarm. That yellow leaf is giving up its nitrogen and thus its green color to the rest of the plant. No problem for a mature plant, just your cue to fertilize if it bothers you. A single hole in a leaf means even less, although I do turn the leaf over in case the culprit is poised to do more.

Cultivate Change
Some changes happen now that can be worrisome but are also celebrated as heralds of the shift in seasons. Obviously, seed pods begin to ripen on a lot of plants now, and the question becomes whether to leave or cut them off. If I do not want the seed, I decide by the age of the plant and how attractive the pods are. One of my favorites to leave is rose hips because the birds are such fun to watch as they feed on them.

I cannot bring myself to remove aging hydrangeas from the shrubs that bloom only once. Let them dry on the plant until they reach a nice shade of tan with blue and green splotches and then clip the flower heads to fill a glass vase. Other nice naturals to let go include magnolia seed pods that turn a bright crimson and the beige beauties that are grass plumes on fountain and pampas grass. These changes tell me that, even on a blistering hot day, autumn is on its way.

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