Did you hear about the gardening couple who was desperate to find a home for their excess zucchini? After facing rejection from nearly everyone, they wrapped each large zucchini in a cute blanket and left them on people’s doorsteps.

Although some aspects of gardening are winding down a bit, the upcoming month of September is a busy one. If we rank months by yard and garden activity, September is second only to May.

The following is a checklist of September’s lawn and garden tasks.

  • September is the most beneficial month to fertilize a lawn, around Labor Day. Fall fertilizing increases stored energy reserves that makes grass healthier and more disease resistant and promotes a deeper root system, which makes the turf more vigorous next spring and summer.
    Labor Day is a prime time to fertilize lawns or seed bare spots. David Samson / The Forum
    Labor Day is a prime time to fertilize lawns or seed bare spots. David Samson / The Forum
  • September is a preferred month to dethatch the lawn using a power rake if the lawn has excessive thatch buildup. Thatch is the tan, undecomposed layer above the soil. One-half inch is considered desirable. If the lawn’s soil is compacted, aerating with a core aerator that brings up little plugs of soil can increase air and water penetration.
  • Weed control is more effective in fall than spring because weeds are moving materials downward in preparation for winter and they carry weed-killing herbicide to the roots very efficiently, resulting in better kill. A mid-September herbicide application can help control hard-to-kill weeds like thistle, creeping Charlie, wild violets and others.
  • September is the best month for seeding new lawns or reseeding bare patches in existing lawns. Seeding should be completed by Sept. 15 or 20 so grass germinates and establishes before winter. Because lawns are long-term investments, skip grass seed bargains and instead choose quality mixes with at least 50 percent Kentucky Bluegrass cultivars. Use blends high in creeping red fescue if the area is shaded.
    Select high-quality grass seed containing at least 50% Kentucky Bluegrass cultivars. David Samson / The Forum
    Select high-quality grass seed containing at least 50% Kentucky Bluegrass cultivars. David Samson / The Forum
  • September is a great month for planting trees, shrubs and perennial flowers. Fall root growth gives them a head start versus waiting until next spring.
  • Most pruning should wait until early next spring. Wounds heal slowly in fall, leaving cut twigs open to winter injury. Other than pruning off spent flowers on shrubs like spirea, there’s little or no reason to prune or cut back any shrubs in fall. Wait until spring instead.
  • September is the month to divide, plant or relocate peony, daylily, true lily and bleeding heart. August is best for iris, but September works also. Always water well immediately after replanting.
  • Rhubarb can be divided or moved around Labor Day. Portions of the plant can be dug away with the mother plant remaining in place, or the entire plant can be dug, divided and reset.
  • Garlic, which needs a cold over-wintering treatment, is planted in late September or early October.
  • Bulbs, corms and roots that don’t survive winter outdoors, like gladiolus, caladiums, tuberous begonias and dahlias, should be dug about the time of the first light frost and readied for storage.
  • Hardy spring-flowering bulbs like tulips can be planted now until mid-October. Daffodils must be planted as soon as possible in September. Water well after planting, because bulbs must produce new roots this fall.
  • Cuttings of geraniums and coleus rooted in September can be grown indoors as houseplants all winter and planted outdoors next spring. Root 4-inch cuttings in a mixture of half peat moss and half sand in recycled greenhouse four-packs. Locate in filtered shade outdoors and pot into 4- or 5-inch-diameter pots when they’re rooted in two or three weeks. Move indoors before nights become chilly.

ARCHIVE: Read more of Don Kinzler's Growing Together columns

Newsletter signup for email alerts

Don Kinzler, a lifelong gardener, is the horticulturist with North Dakota State University Extension for Cass County. Readers can reach him at donald.kinzler@ndsu.edu or call 701-241-5707.