Extension

Trees and Shrubs

• Resume planting trees and shrubs as temperatures begin to cool from the heat of summer. Fall planting allows roots to establish before the following summer, but newly planted material will still require consistent watering. 
• Continue watering newly planted and recently established trees and shrubs during dry periods. Do not assume cooler temperatures eliminate the need for supplemental irrigation.
• Avoid late-season fertilization of woody plants. Tender new growth stimulated late in the season may be more susceptible to winter injury.
• Inspect trees and shrubs for dead, damaged, or diseased branches. These can be removed as needed, but major pruning of healthy growth can generally wait until the appropriate season for the species.
• Watch for and control any late infestations of tree webworms.
• Twig girdler insects should be controlled if large numbers of small branches of elms, pecans, or persimmons are uniformly girdled from the tree and fall to the ground

Flower Beds

• Begin planning locations for spring-flowering bulbs. Purchase healthy, firm bulbs when selections are good, even if planting will occur later in fall.
• Watch for fall specials at garden centers and nurseries since fall is a great time to plant many ornamentals.
• Collect seeds from favorite open-pollinated annuals and perennials as seed heads mature and dry.
• Divide and transplant spring- and early-summer-blooming perennials as temperatures cool off. Water newly divided plants thoroughly during establishment.
• Continue monitoring flowers and ornamentals for spider mites, aphids, caterpillars, and other late-season pests. Treat only when populations or damage justify control

Vegetables

• Continue planting appropriate cool-season vegetables according to HLA-6009 Fall Gardening. Lettuce, spinach, radishes, mustard, turnips, and other quick-maturing crops can provide fall harvests.
• Keep newly seeded fall vegetable beds consistently moist during germination. Warm, dry soil can cause rapid drying of the upper soil surface.
• Place advance orders for garlic early to secure desired varieties. Begin preparing planting areas for garlic even though planting is generally delayed until later in fall. Select a sunny, well-drained site and incorporate needed amendments based on a soil test.
• Continue harvesting peppers, tomatoes, eggplants, okra, and other warm-season vegetables regularly while plants remain productive.
• Remove declining or diseased vegetable plants as production ends. Do not compost plant material heavily affected by disease.
• Scout fall brassicas for caterpillars such as imported cabbageworm, cabbage looper, and diamondback moth larvae. Small larvae are generally easier to manage than established populations.
• Prepare unused garden areas for fall cover crops where appropriate. Cover crops can protect bare soil, suppress weeds, and add organic matter.

Lawn and Turf

• Last nitrogen fertilizer application of the year on warm-season grasses should be applied no later than September 15th. (HLA-6420) Lawn Management in Oklahoma
• Winter broadleaf weeds like dandelion will begin to emerge in late September, which is also the best time to control them with a 2, 4-D type herbicide.
• If pre-emergent control of winter-annual weeds (henbit, chickweed, annual bluegrass, etc.) is desired in lawns, the application should be completed by the 2nd week of September. (HLA-6421) Controlling Weeds in Home Lawns. Note: Do not treat areas that will be seeded in the fall. 
• Continue bermudagrass spray program with glyphosate products for areas being converted over to tall fescue this fall. (HLA-6421) Controlling Weeds in Home Lawns
• Plan to seed bluegrass, fescue, or ryegrass as needed in shady areas in mid- to late-September. Fall is the best time to establish cool-season lawns (HLA-6419) Establishing a Lawn in Oklahoma.
• White grub damage can become visible this month. Apply appropriate soil insecticide if white grubs are a problem (EPP-7306) Ornamental and Lawn Pest Control (For Homeowners). Water products into soil.

Fruit and Nuts

• Harvest apples, pears, grapes, and other fall-ripening fruit as they reach the appropriate stage of maturity.
• Continue watering fruit and nut trees during extended dry periods. Adequate moisture remains important after harvest and as perennial plants prepare for dormancy.
• Remove fallen, damaged, or mummified fruit from around trees and vines to reduce overwintering sites for insects and disease organisms.
• Avoid late-season nitrogen fertilization of fruit trees, which may encourage tender growth going into winter.

General

• Fall is an excellent time for soil testing. Results can help guide fertilizer, sulfur, lime, and other soil amendment decisions before the next growing season.
• Continue maintaining compost piles by keeping them as moist as a wrung-out sponge and turning them periodically to maintain decomposition.
• Evaluate this year’s garden while successes and challenges are still easy to remember. Record cultivars, planting dates, pest problems, and other observations that may be useful next season.