By all these lovely tokens
September days are here,
With summer’s best of weather
And autumn’s best of cheer.
-Helen Hunt Jackson, “September”
September heralds the fall gardening season with cooler temperatures and a first taste of autumn in the air. Zones 1-4 will likely experience a first frost, while warmer zones look forward to relief from the late summer heat and drought. September also marks the autumn equinox, when day and night are the same length, and the waning daylight hints at the winter to come.
Now’s the time to be outside to enjoy the beautiful weather while taking care of some of the following lawn and garden tasks for September.
Annuals and Perennials
- Divide and/or transplant perennials, making sure to feed the roots with a good source of phosphorus.
- Don’t disturb asters, chrysanthemums, Russian sage, ornamental grasses, or other plants that are of interest in the fall and winter.
- September is the month to plant or transplant peonies.
- Plant annuals such as ornamental cabbage, pansies, violas, and snapdragons.
After first frost in zones 7 and below, dig up and store tender bulbs such as caladium, canna, taro, elephant ear, dahlia, and tuberous begonia.
Dogwoods show off red berries against a backdrop of green leaves
Shrubs and Trees
- Container grown trees and shrubs can be planted now.
- Remove any dead shrubs and trees.
- Transplant trees and shrubs after the leaves begin to turn.
- Clean up fallen fruit to deter pests and disease.
- Address diseases now. Remove and destroy (do not compost) unhealthy leaves and branches after treating.
- Remove spent blooms, but don’t do any heavy pruning that would encourage new growth which would be killed by the first frost.
Hold off on fertilizing trees and shrubs to allow them to harden before winter.
- Plant late-season vegetables such as peas, broccoli, cauliflower, cabbages, kale, brussels sprouts, leeks, lettuce, radishes, turnips, and onions.
- Once your vegetable garden is finished, plant clover, alfalfa, or legumes as a cover crop. These “green manures” can be plowed under in the spring for a natural fertilizer and soil conditioner.
- Bring houseplants indoors before the nights get too cool.
- Prepare for Christmas color! Place poinsettias and Christmas cactus indoors where they will receive 10 hours of bright light (and 14 hours of total darkness) each day. A Christmas cactus will need a cool spot (50-60 degrees), while poinsettias are OK at 65-72 degrees.
Plant some spring-flowering bulbs in pots to enjoy over the winter. If you intend to force early blooming for the holidays, put your bulbs in the refrigerator now.
- The first half of September is prime lawn time! Take advantage of the season to ensure a strong, tough lawn in the future.
- Start with core aeration and dethatching, leaving about ½” of thatch to decompose.
- If you are planting seed, or if your lawn is thin or weedy, sow seed before mid-month. Let the new shoots grow through 2-3 mowings before applying regular-strength fertilizer or a “weed and feed” product.
- Fertilize with a 3-1-2 fertilizer to encourage top growth and winter hardiness.
Cleanup and Maintenance
- Now is a great time to clear out new planting beds and apply compost (or leaves and grass clippings) to be ready for spring planting.
- Attack those weeds! Commercial herbicides are particularly effective this time of year, as weeds are storing up nutrients in their roots and quickly absorb the herbicide where it counts.
- Check out our videos on how to safely target weeds and organic weed control using vinegar.
- Label your perennials and bulbs before they die back to the ground.
Put out extra bird feeders to support migrating birds.
Slugs are particularly active in September – apply slug bait, diatomaceous earth, or other slug-control products during this time.
In the fall, slugs lay clusters of eggs about the size of a small BB. Look under stones, boards, and around the edge of your lawn for these colorless eggs and destroy any you find.
- If you haven’t already ordered your fall bulbs, do so now! Hold off on planting them until after the first frost.
- Simplify leaf clean-up by installing gutter guard, covering open drainpipes, and tuning up or repairing lawn equipment.
- Build a compost bin to collect fall leaves.