September Gardening By the Month

“My green thumb came only as a result of the mistakes I made while learning to see things from the plant’s point of view.” ~H. Fred Dale (Thanks, Anne)


(You should be well on your way to preparing and transplanting your fall garden beds.)

summer-flowers-55537_6401st WEEK:

Apply iron foliar treatments to chlorotic (yellow) plants and St. Augustine grass, but wait until Oct. 1 for winter lawn fertilizers.

Plant perennials like Asters and Garden Mums for fall color.

Order spring bulbs for later planting. Most require a six-week stay in the refrigerator before planting.

If tomatoes have been in the ground and are growing, now would be a good time to apply a slow-release fertilizer. Plant green beans, radishes, carrots, beets, squash and sweet corn for fall (transplant broccoli, brussels sprouts, cabbage, cauliflower also. A protective cover such as Grow Web will counter any searing sun. – EO).

Finish pruning cold-tender shrubs now to avoid having new growth killed back by first frosts.

For summer-planted trees and shrubs, make sure you water the root ball. Roots are confined to that area for the first few months.

The brown scorching symptom you see on citrus, bur oak, ivies and other leaves is likely the result of sunburn. When temperatures fall, the symptoms will cease.

If leaves and pecans are dropping, it is in response to heat and dry weather. Watering deeply at the drip line once a month will help. (Watering deeply at this time will also help maximize nut filling -DP).

If the lawn is dying in patches, check for CHINCH BUGS or a fungal disease.

This is probably the last week to seed Bermuda grass without a high risk of freeze-damage (buffalo grass seed can planted also – LR). Prepare the soil and water twice a day until a good stand appears – usually about a week.  – CF

If you haven’t already, prepare garden soil now for fall/winter vegetable transplants by adding 2″ of compost and tilling to a depth of 6″ to 8″.

If your yard needs more trees, research recommended varieties, taking note of mature sizes and heights so you can plant in fall, the BEST time to plant trees, shrubs and woody perennials. – EO

Use glyphosate-type herbicide to eliminate all existing grass and weeds in areas you intend to develop this fall or next spring as cultivated beds. Application must be made several weeks before first killing freeze. – NS

Clean up iris beds and thin out clumps, if crowded. – LR

chrysanthemums-1987_6402nd WEEK:

Fall is for planting. Plant garden mums and fall marigolds (choose mums and marigolds that are just about to bloom). Plant hardy trees, shrubs, vines and groundcovers from now until mid to late November.

If rains pick-up, you may see a NUT GRASS invasion. Control it with herbicides such as Image, or Manage. Read product labels carefully before purchasing to match the herbicide with your particular conditions. Products must be applied during growing season. Two applications are usually needed.

It is not too early to divide irises, day lilies and shasta daisies. Two or three years without dividing can reduce blooms. (Use a sharpshooter shovel to divide the clumps and transplant into full sun areas. Remove 30 to 40% of the foliage of the transplants in order to reduce stress. – LR)

Remove seed pods from esperanza and poinciana so they will keep blooming.

When you water container plants, water until the moisture drips out of the drain hole to make sure a salt layer does not form.

Watch for the SOPHORA CATERPILLAR on Texas mountain laurels. They can strip a plant of leaves quickly. Control with Bacillus thuringiensis as soon as activity is noticed.

Cut at ground level the suckers that emerge from the roots of peaches, plums, pears, apples, Oriental persimmon and citrus to prevent the rootstock from taking over the fruiting top (scion).

With hot, dry weather after a cool, wet spring, many deciduous trees may lose their leaves early. Use the leaves for mulch or in compost.

Lawnmower blade height can be lowered 1/2″ to 3/4″.

Don’t be too hasty. Pansies, Johnny-Jump-Ups and Snapdragons are set out after Columbus Day. Hot weather will kill them. – CF

To attract butterflies, plant mist flower (eupatorium), lantana, milkweed (asclepias), buttonbush (cephalanthus), Mexican mint marigold (Tagetes lucida), and indigo spires sage. See our butterfly list for more host and nectar plants.

Add compost to flower beds to boost tired flowers.

Prepare beds for spring-flowering bulbs by adding a generous amount of organic matter such as compost. Bulbs need good drainage so raised beds might be necessary. – LR

yellow-red-daylily-114473_6403rd WEEK:

As night-time temperatures start to come down, let your lawn (especially like “Raleigh” St. Augustine) dry out between waterings and water only in the mornings in fall to prevent brown patch fungus. If round, brown areas appear in your lawn, treat with Daconil, Terrachlor, Fungaway or another fungicide labeled for the problem.

Dig and divide spring or summer blooming perennials.

It is time to apply a pre-emergent herbicide to prevent winter weeds in the dormant lawn. We like Amaze or Dimension, but read the labels to see which best suits you. Weed control with a pre-emergent is especially necessary for buffalo grass lawns that are kept short. Failure to apply pre-emergent herbicides permits cool-season weeds to germinate and you will be in for a long fight. Follow up in October with fertilization as a well-fed/healthy lawn chokes out weeds and is your best defense against them. – CF

Fertilize tomatoes with 1/2 cup of lawn fertilizer per plant when the first fruit sets. Spread fertilizer over the roots of the plants.

Pepper sauce seems to be effective (for awhile, then switch to a new tactic) for protecting plants from both squirrels and deer. Apply weekly.

If the temperatures are cooling, oak wilt fungal mats may appear on diseased red oaks. Paint all wounds on Spanish oaks and live oaks to prevent new infections (Even if the daytime highs are hot enough to keep oak wilt from being active, play it safe by applying pruning paint to all wounds more than 1 inch across-EO ).

Plant shade trees now to take advantage of mild fall and winter weather for root development. Fall is the optimal time for planting trees.

To attract hummingbirds, plant cardinal lobelia, trumpet vine, lantana, Turk’s cap, autumn sage. Plant woody perennials now (best time of year) or plan to incorporate them into your landscape in spring.

Control PILLBUGS in your veggie garden and in newly-germinated wildflowers with bait, Sluggo Plus, or Sevin dust.

Divide perennials such as daylilies and irises. Use a sharpshooter shovel to divide the clumps and transplant into full sun areas. Remove 30 to 40 % of the foliage off the transplants to reduce stress.

FIRE ANT mounds will appear after good rains. Treat mounds in the lawn and flower beds with Amdro or other fire ant baits. Be sure to use only around the outside edges of the vegetable garden and not inside. (Try a bucket of soapy-sudsy water on the mound, the ants hate it!) – LR

nut-316317_6404th WEEK:

Fall is here! (equinox: the time when the sun crosses the equator, making night and day of equal length in all parts of the earth.) – SB

Apply pre-emergents to control winter annual weeds. Some are for turf, others for beds, veg. gardens; double-check.

Make sure your Crape Myrtles are starting to go dormant. If not, stop watering and remove their mulch.

Perform final pruning of hardy shrubs and vines; but not those which bloom in spring.

Still time to sow wildflower seeds in your landscape, as well as in waste places around your neighborhood. Good soil preparation will yield better germination. At minimum, the seeds must touch bare soil, and light must penetrate to the soil.

Treat rust on zoysia grass or figs with Bayleton or another labeled fungicide. If fruit tree leaves show rust, apply wettable sulfur to prevent them from dropping all their leaves.

Get ready to fertilize your lawn using a “winterizer” formula. Buy a fertilizer that is 15 to 18 percent nitrogen and apply to lawn around Oct. 1. Rainbow Garden’s fall formula 18-6-2 is especially formulated for San Antonio lawns, trees, shrubs, and beds. A 40lb. bag covers 7200 sq. ft.

The organic material in raised beds decomposes and compacts as we garden. Replenish now with compost to get ready for fall vegetables.

As average temperatures drop, be careful not to overwater your lawn. Lawns require less water in fall. Always water in the morning to avoid developing fungus issues. – CF

Look for the Pawnee variety of pecan to mature its nuts soon, it is probably the best pecan variety for the San Antonio area because it is very productive and naturally resist aphids.

Wait for our first cool spell before setting out plants to provide cool-weather color. Try ornamental kale for colorful, fringed foliage with inner leaves of red, white, rose and pink. Dianthus, calendulas, stock and snapdragons offer flowers in a wide range of hues. Sow seeds of snapdragons, dianthus, pansies and other winter flowers in flats for planting outdoors in October.

Lightly prune and fertilize geraniums and begonias for further blooming. -EO

Dig and divide spring bulbs and perennials such as daffodils, irises, daylilies, liriope and cannas.

Root prune established plants you intend to move this winter to allow them time to establish new roots within the soil balls that will be lifted. Do not cut tap roots at this time.

Mums are setting buds now. Pinch off about 1/3 of the buds to encourage larger flowers in fall. Fertilize them with a balanced fertilizer such as 20-20-20 to increase flowers and healthy foliage. – LR

Lay mulch in your flowerbeds by the end of this month. Winter weeds will be germinating soon and this layer of mulch will save you hours of weeding.


Many thanks to my contributors:
CF – Calvin Finch, Bexar County Extension Agent for Horticulture, Texas Agricultural Extension Service.(courtesy S.A. Express-News)
EO – Edna Ortiz, Bexar County Extension Agent for Horticulture, Texas Agricultural Extension Service.(courtesy S.A. Express-News)
NS – Neil Sperry, Texas horticulturalist, Publisher “Neil Sperry’s GARDENS” and contributor to S.A. Express-News, visit his web site at
LR – Lynn Rawe, Bexar Co. extension agent for horticulture (visit their web site at, Texas Cooperative Extension. (courtesy S.A. Express-News)
DMS – Diane Morey Sitton, gardener, writer and contributor to Neil Sperry’s GARDEN’S Magazine.
DP – Diane Pfeil, Bexar County extension associate for horticulture, Texas Cooperative Extension.
WN – William Niering, PhD. (began a program called SALT-Smaller American Lawns Today)
AJW – A.J. “Pop” Warner, from his book “A Year In The Rose Garden”
HG – John Howard Garrett, aka the “Dirt Doctor”, visit his web site at
SB – Steve Brown, meteorologist for KSAT 12. (visit their web site @
NR – Nathan Riggs, Extension Agent, Integrated Pest Management-Bexar Co. (courtesy S.A. Express-News)