September Gardening Guidelines

by Keith C. Hansen, Extension Horticulturist, Smith Co. – Tyler, Texas

September is a swing month in the southern gardening world with the official arrival of Autumn later this month, and hopefully, a return of cooler and wetter weather. Despite the heat that lingers this month, September is still one of the better times of the year to be gardening, especially for planting landscape plants.

September is also the month for new learning opportunities. The Fall Gardening Conference & Bulb Sale, sponsored by the Smith County Master Gardeners, is always on a Saturday in October. Check the East Texas Gardening Calendar for the date and details on what is always a well-designed free program for home gardeners with well-known speakers.


Folks will want to pay attention to lawn care this month. The hot, dry weather could encourage chinch bugs which can turn St. Augustine into what looks like a drought-stricken lawn.

September is also the time to apply lawn fertilizer to keep the grass healthy and growing up to first frost. Fall fertilized lawns are better equipped to make it through the winter and resume growth next spring than lawns that receive no fertilizer.

Did you have weeds last spring before the grass started growing? These would have been cool-season weeds which germinated last fall. A pre-emergence herbicide (weed preventer) applied this month will help reduce the recurrence of the same weeds next spring (unless they are perennials like dandelions). Avoid pre-emergent herbicide applications on newly planted, or weakened grass or in dense shade. Carefully follow label rates of application, since applying more than is called for can damage your lawn.

Lawns that suffered dieback from drought, chinch bugs or disease can be safely sodded in September. It’s too late to try to establish Bermuda or Centipede from seed, but ryegrass and tall fescue can be sown toward the end of the month.

Fall is also a good time to test your soil, especially to determine the pH which tells you the acidity of the soil. Strongly acidic soils are corrected with an application of lime. Keep in mind that it takes a few months for the lime to react with your soil, and that you may need to reapply lime every few years.


If you enjoy growing wild flowers, collect seed for your garden from summer bloomers for sowing next spring. Also, save seeds from favorite self-pollinating, non-hybrid garden flowers such as marigolds, cosmos, gomphrena, coneflower, coreopsis, Rudbeckia and zinnias by allowing the flower heads to mature. Lay seeds on newspaper, turning often to dry; then store in glass jars or envelopes in a cool (40 to 50 degrees F), dry, dark place.

Sow spring wildflower (like bluebonnets) seed now. For more reliable, uniform seed germination of our State flower, purchase acid-treated bluebonnet seed. This treatment pits the seed coat, allowing nearly 100% germination in one to two weeks.

Perennial phlox should be divided about every third or fourth year. Early fall and early spring are the best times to plant and transplant them. Divide big clumps into thirds.

Create new perennial flower beds, and dig, divide, and replant overcrowded beds of cannas, irises, daylilies, daisies and other perennials. Spread a liberal amount of organic matter evenly over the area and mix into the soil at least 6 to 8 inches deep. Space divisions at least 1 foot apart in all directions so root competition will not be a problem for several years.

Purchase spring blooming bulbs as soon as they become available in the garden centers, or mail order special varieties. Smith Co. Master Gardeners will hold a Fall Bulb Sale of hardy but less common bulbs in the fall. Tulips and hyacinths should be stored in a refrigerator until November.

Plant bulbs by loosening the soil and make a hole with a trowel or bulb planter. Don’t mash the bulb into the soil or you may damage the basal plate (bottom of the bulb), causing it to rot.

Tip back roses the first week of September if you didn’t last month to stimulate a new flush of growth for a final burst of fall color. Don’t take off much, cutting back only a quarter of the growth. Make a light application of fertilizer, and watch for black spot disease which can be a problem once frequent rains return.


Frequently check the soil around first-year trees and shrubs with your fingers to make sure the root ball and soil are getting enouhg water. At the same time, take care to not keep the soil soaking wet. Just because it’s hot doesn’t automatically mean the soil is dry 3 or 4 inches deep. Check it out that deep to be sure.

Examine your flower, ground cover and shrub beds for seedlings of privet, sweetgum, oaks, elms, blackberry, greenbriar, sedges and other unwanted weeds. If they are already well established, wait for soaking rains to soften the ground when they’ll be a little easier to pull. A pair of pliers may also help get woody plants out of the ground.

Pine needles will soon be abundant. Collect and use them as a long lasting mulch around shrubs, young trees, and in vegetable gardens and other places where weed control and water conservation is needed.


Plant beets, broccoli (plants), Brussels sprouts, cabbage, carrots, cauliflower (plants), Swiss chard, collards, kale, garlic, lettuce, mustard, parsley, English peas, radish, spinach and turnips this month. Soak seed furrows with water before sowing seed, and mulch lightly. Water the rows daily in hot weather to promote germination and growth of young seedlings. Treat cabbage, broccoli, and cauliflower with Bt (Bacillus thuringiensis) as needed to prevent damage from cabbage loopers.

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