Guest column: Gardening tips for September

The Daily Ardmoreite
Pat Neasbitt
Master Gardener

Although September is still pretty much a summer month in Oklahoma, it means that cooler fall weather and more rain are soon to follow. Even though the autumn equinox is the official start of fall on September 22nd, plants are still growing and need the same care they needed all summer. It’s still almost 100 degrees, and I know I am really tired of dragging hoses to keep everything watered, deadheading to keep things blooming, and keeping on top of weed removal; however, what we do in the garden now is extremely important because it determines the success of our spring gardens. September is a good time to do the following:

Watch for specials at garden centers and nurseries. 

Fall is a great time for planting perennials, ornamental grasses, shrubs, and trees. Even when the air gets cooler the soil will still be warm so roots can grow and get established before the uncertainties of spring weather.

Order spring-flowering bulbs as soon as possible.

You want to plant them between Halloween and Thanksgiving each year, but if you wait until then to buy them, they may be picked over or gone. You can keep them in the refrigerator until planting time, and almost all bulbs require about 6 weeks of cold temperatures before planting. Meanwhile, get the beds ready by adding compost to improve the soil and drainage. Bulbs will rot in waterlogged, heavy clay soil. Raised beds with compost added will remedy this situation. Raised beds will also help lavender, rosemary, and succulents survive because of better drainage.

Get houseplants ready to come inside.

Get houseplants ready for the winter by putting them in more shade to acclimatize them to lower light so they won’t go into shock and drop all their leaves when moved.

Plant cool-season vegetables through September.

These include lettuces, radishes, mustard, and spinach. You have until the middle of September to plant swiss chard, garlic, and turnips.

Fertilize Bermuda lawns

If necessary, put down a pre-emergent to control winter/spring weeds by September 15th.

Don’t fertilize trees, shrubs, or ornamentals

Don't do it now because they need to begin going dormant and using their energy for root growth and winter survival. Any tender new growth as a result of fertilizer application now is susceptible to insect and early frost damage. Grasshoppers are plentiful, and they just love the tasty tender fresh shoots on plants.

Annuals in container plantings need fertilizing about every 2 weeks with fish emulsion, seaweed extract, compost or manure tea, or water-soluble fertilizer for the best show until frost.

Transplant spring-blooming plants

You can divide and transplant spring-blooming plants in the latter part of September when it should be cooler and there should be more rain. These include lilies, daylilies, irises, daisies, cannas, violets, gaillardias (blanket flowers), coneflowers, liriope, and peonies. Don’t plant peonies more than 2” deep or they may not bloom. Amend the planting beds with compost before replanting divisions.

Don’t prune some plants

Don't prune spring-blooming trees and shrubs such as forsythia, redbud, flowering quince, mockorange, ninebark, rhododendron, weigela, viburnum, and bigleaf and oakleaf hydrangeas until after they bloom next spring because they bloom on this year’s growth – old wood.

Have fun with some fall containers.

The tried-and-true mums, pansies, asters, and ornamental cabbages and kales are always great. For added interest try some swiss chard ‘Bright Lights’, sedums, pineapple sage, autumn sage, ornamental peppers, perovskia (Russian sage), and ornamental grasses. Container gardens are easy and fun. There is no right or wrong, just different. The rule is to have fun and do what you like. Happy Gardening!