September Gardening Tasks
Expand the categories below to learn more about what you need to do this month.
Soil Testing
Test the soil in your beds in Fall for plant nutrients and lime needs. Soil tests usually take 10 days, so test now to have the results when you plant bulbs and beds. Soil test bags are available at the extension office. It is important to till in any needed lime (if any) for faster soil pH adjustment. You should also incorporate any needed phosphorus at this time.
Vegetables
If not done in August, prepare now your cool fall vegetable garden. Using transplants from your local garden center will get the garden off to a fast start, but seeds and home-grown transplants provide a wider variety from which to choose.
Plant herbs that thrive in cool weather. Some to try are parsley, thyme, sage, dill, fennel, garlic, comfrey, and cilantro.
About early to mid-September, you can start planting things like globe artichokes (it’ll need mulch), Jerusalem artichokes, mustard greens, turnips, spinach, lettuce, fall potatoes (mid-August to early September), collards, rutabaga, broccoli, bunching onions, leafy celery, cilantro, cabbage, etc.! Potatoes are always thought of as a spring crop, but do very well in the fall months. In fact, fall and winter are the best times for many cool season crops in our area. Call the Hall County Extension if you need advice on fall plantings.
Finish cleaning up around your garden and get rid of dead plants and leaves as many diseases overwinter on infected dead leaves and stems.
Although strawberries are perennial, think about planting an annual strawberry bed this year. Plant plugs of ‘Camarosa’ or ‘Sweet Charlie’ in late September to early October and harvest the next spring. Apply about 1/3rd to ½ of the needed fertilizer this fall and apply the balance in early spring. This is the way commercial growers do it these days, and they avoid disease and pest issues inherent in perennial strawberry plantings.
Harvest mature green peppers and tomatoes that are in the white or pink stage before the frost gets them. You may not see frosts until November, but be prepared.
Harvest herbs and hang upside down to dry in a cool, dry place.
Lawns
Watch for problems with brown patch and dollar spot in warm season grasses, especially if you had problems with one of them last year. If you haven’t done it, put out an approved pesticide for the grubs this month.
Late summer is a good time to topdress lime established lawns if needed (based on a soil test of course). Don’t just add lime because you think the yard might need it!
Healthy grass is the best defense against weeds. Avoid “weed and feed” products; only apply post-emergent herbicides to areas with weed infestations. Put out a pre-emergent herbicide for winter and spring weeds (like chickweed and henbit) by mid-month.
Some homeowners like to overseed their Bermuda lawns with ryegrass for a green winter lawn. Mid-September to early October is the best time to do this (you can’t use pre-emergents if you plan to overseed a lawn!).
This time of year is a good time to aerate established cool season tall fescue lawns (aerate warm season lawns in late spring or summer). If you are planning a new fescue lawn, make sure you apply any needed limestone and phosphorus before you plant.
If you plan to plant a new cool-season (tall fescue) lawn, the best time to plant is between September 15 and October 15 (you can’t use pre-emergents if you plan to seed a new lawn!). Tall fescue is the most shade-tolerant turfgrass for our area (St. Augustine is good too, but is marginally hardy here). Lawns that have both shade and sun are excellent for tall fescue. Dappled shade is best and fescue will die in constant deep shade. Make sure you fertilize tall fescue at establishment or for established turf for maintenance. If establishing a new lawn, make sure you follow a soil test recommendation and incorporate any needed phosphorus or lime!
Continue treating fire ant mounds until it cools down, first with bait and then follow with a drench for effective control.
Flowers
If you haven’t already done it, it's time to buy your spring-flowering bulbs such as daffodils, tulips, hyacinths, and crocus. Don't plant them yet - wait for cooler weather, but store them in a cool place where temperatures will be 60 degrees F or lower (the crisper in your refrigerator is ideal). This is also a great time to divide spring and summer blooming perennials. If summer beds need refreshing, try ageratum, celosia, zinnia, and wax begonia for color into fall.
Divide perennials, especially spring bloomers. Remove seedheads from perennials to prevent reseeding in the garden. Plant new chrysanthemums for fall color. Dig gladiolus as foliage begins to yellow and air dry before storing for winter. Clean up garden areas to reduce insects and disease as plants die back for winter.
Trees
Think about where you might like some new trees or shrubs. Fall is a good time to set new material in your landscape! Plant fall trees and shrubs, both deciduous and evergreen. Rake up fallen leaves and compost. Prune broken and dead branches from trees. Avoid pruning spring-flowering shrubs such as azalea and forsythia to ensure spring flowers.
Houseplants
If houseplants are outdoors and are actively growing, you can fertilize foliage plants like ferns at 1 tsp. of a water-soluble fertilizer like 20-20-20 or 24-8-16/gallon of water once every 1-2 weeks. Water to leach out of the container. If the plant is a flowering plant in a pot such as impatiens, coleus or petunias/million bells, use 1 tsp. of a water-soluble fertilizer like 20-20-20 or 24-8-16/gallon of water once every 1 week. Water to leach out of the container. If the plant is a succulent such as jade plant, use ½ tsp/gallon of a high nitrate fertilizer like 20-10-20 once a month.
If houseplants are indoors and in subdued lighting, fertilize once a month with a water-soluble fertilizer (1 tsp./gallon/month).
In late September, start to bring plants in before temperatures drop into the fifties at night. Many true tropicals in containers can get chill injury from temperatures as high as 50 deg. F! Clean and wash before moving indoors to reduce insects. Fertilize lightly before winter conditions arrive and growth slows. Saved poinsettias and holiday cacti can be forced into late November to Christmas blooming by starting dark treatment of short days – consult the Hall County Extension for details.