By David W. Marshall, Extension Agent Emeritus
August brought brutal heat to our area this year. But thankfully we also got much-needed rain, which relieved some of the heat stress on our plants. Tropical storm development in the Atlantic has been minimal so far this season, but by the time you read this, that may have changed. September is usually a transitional month for us, often still very hot and humid, yet withsubtle signs that the seasons are about to change. For the gardener, that means there’s work to do.
If you have planted the right plants, fall can be a very colorful time of year in your home garden. There are several easy-to-grow perennials that have had all season to recover from last year’s cold winter and should now be flowering heavily until the end of fall. Among the best is firebush (Hamelia patens), a large bushy perennial that, if grown in a sunny location, will be full of dark red-orange flowers this time of year. Hummingbird and butterfly visits to these flowers are frequent. Other excellent fall-blooming perennials include cigar flower (Cuphea micropetala) and various species of Salvia such as Mexican bush sage (Salvia leucantha) and pineapple sage (Salvia elegans), as well as Turk’s cap (Malvaviscus spp.), for sunny areas. Firespike (Odontonema cuspidatum) is an excellent long-time favorite for partially shaded areas. Visit nurseries now to see other options so you don’t miss out on one of our most colorful seasons.
In mid-October you can begin planting cool-season annuals such as petunias, Calibrachoa, Nemesia, Diascia, Dianthus, Verbena, Alyssum ‘Snow Princess’, and wallflower (Erysimum spp.). In late October to November add pansies and violas. Practically all the cool-season annuals will need full sun. Don’t forget the option of container plantings which quickly add color to sunny porches, patios, or decks. If you wish to add some flowers before mid-October, you can still plant warm season annuals such as angelonia, torenia, zinnias, or melampodium. They will likely last until late November or early December when we usually have a freeze. You can still plant pentas in a sunny area. Visit local nurseries for many options.
This is the time of year to be especially alert for signs of tropical sod webworm damage in the lawn. Watch for off-color or thinning areas of grass, which, with closer observation, will reveal that grass leaves are being chewed. The damage can increase rapidly and warrant insecticidal control. The caterpillars feed at night and are difficult to find during the day, when they rest deep in the thatch layer.
If you confirm sod webworm damage, apply a lawn insecticide that lists control for sod webworms on the label. There are some granular formulations which can be applied with a fertilizer spreader. But they must be watered in to activate them. Liquid insecticide formulations, applied with a hose-end sprayer in the recommended amount of water, can also be used. No matter which insecticide you use, monitor the infestation and damage and be prepared to make another application later as needed. Once the sod webworms start, they will be with us several months, until the weather gets cool enough to stop them. Some of these insecticides also provide control of ticks, which have been especially troublesome this year.
If your St. Augustine grass lawn has thin or bare spots in sunny areas, in early September, you may also choose to apply a low-nitrogen, high-potassium fertilizer such as 5-0-20 or 5-0-15. This can be especially helpful if your lawn has been damaged by sod webworms. But avoid fertilizing with fertilizers which contain more nitrogen (the first number) because the lush growth stimulated by the nitrogen will be more attractive to sod webworms. Centipede lawns probably won’t need this late summer application. Make sure you water the fertilizer in lightly.
Now as we approach fall, be on the watch for new fire ant mounds in your yard. The easiest and most complete control is an application of fire ant bait to your whole yard using a hand spreader. Follow the label directions, and you will find that this is a quick and relatively inexpensive method to control fire ants in your yard for up to six months. The application rate is low and two applications per year are all that are needed. Just be sure that you’re using a bait material and not a contact insecticide. Before you buy an insecticide, read the label directions and be sure that it is appropriate for broadcast application.
Regularly change the water in bird baths and other such areas now so as to prevent mosquito larvae from developing. Anywhere that collects standing water, such as low spots in gutters, can be breeding grounds for mosquitoes. Use insect repellents that contain DEET or picaridin to protect yourself from mosquitoes and ticks when working outdoors, especially in the early morning and evening hours.
If rainfall decreases in late September and October, as it often does, don’t forget to water plants as needed, especially plants that you planted this year. Your lawn should stay green until we have frost and that doesn’t usually happen until November or December. Continue mowing your lawn regularly too as we move into fall. Be especially careful not to mow too low during stressful weather, especially in partially shaded areas.
If cool season weeds trouble your lawn in early spring, apply a pre-emergent herbicide such as atrazine, Dimension, or Gallery in October, when night temperatures fall to 55-60 degrees for four or five nights. Be sure to check the label of any herbicide before buying it to make sure it’s safe on your type of grass and follow directions carefully.
Fall and winter are great times to plant trees and shrubs as long as you remember to water the new plants regularly. Try to add some trees that have fall color, such as Oriental persimmon, crepe myrtle, Chinese pistachio, American hornbeam, Japanese maple, hickory, red maple, sweetgum, ginkgo, bald cypress, and black gum. As we move into fall and the camellia flowering season, it is a good time to visit the nursery to select camellias while in bloom. The sasanqua camellias will be among the first to bloom, generally followed by the japonica types.
As our nights cool in late September, it’s time to start planting vegetables and herbs for the cool season. Seed arugula, beets, cabbage, carrots, cauliflower, collards, lettuce, mustard, radishes, and turnips. Set out bulbing onions and strawberries. In October, add broccoli, Chinese cabbage, kohlrabi, spinach, bok choy, tatsoi, and mizuna. Herbs to seed include cilantro, parsley, French sorrel, salad burnet, sage, and thyme. Be sure to plant in a spot in full sun. Fertilize your plants periodically with a balanced fertilizer such as 20-20-20. If you don’t have much garden space, remember that some of these can even be grown in large pots.
Oriental persimmons ripen in the fall. If you don’t have a persimmon, now is a fine time to plant. Plant it in full sun or at least partial sun. Good drainage is very important, too. Also, plant where you can enjoy the spectacular view of the colorful fruit in the fall. It really is a good landscape plant, though it can be messy when the fruit drops, so it’s best not to plant it near a patio, or where there will be much foot traffic.
Many citrus fruits are well developed and only months from maturity now. Give the citrus its final fertilizing of the year in September. Continue watering into fall as needed as that will help the fruit continue developing well. If you have very young, cold sensitive types of citrus, plan now for those hard freezes that can occur from late November onward. It’s much easier to calmly get the materials together now rather than hurriedly at the last minute when a cold front is approaching.
David W. Marshall is a horticultural consultant and an Extension Agent Emeritus with UF/IFAS Extension Leon County, an Equal Opportunity Institution. For gardening questions, email the extension office at AskAMasterGardener@ifas.ufl.edu.
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