September Yard And Garden To-Do List

September is a busy month around yard and garden. Here’s a monthly checklist of recommended activities.


  • Surprisingly, September is the most important month for lawn care, more important than spring. Research proves grass is more active in fall, and promoting its health in September has the greatest impact on vigor next spring and summer.
  • Early September is the most beneficial time to fertilize lawns. If you’re only going to fertilize once per year, do it in the fall instead of spring. Fall fertilizing makes lawns green up quicker in spring and deepens its root system, making it more drought tolerant. If a second application of fertilizer is desired, apply around Memorial Day.
  • Check the lawn’s thatch layer, which is the tan, undecomposed layer between grass blades and soil. If it’s thicker than one-half inch, September is the preferred month to dethatch the lawn by power raking or core aeration.  If the lawn’s soil is compacted, aerating with a core aerator in September can increase air and water penetration.
  • Lawn weed control is more effective in fall than spring because weeds are moving materials downward in preparation for winter and they carry weed killer to the roots very efficiently, resulting in better kill. There’s also less chance of spray drifting onto vegetable gardens and flowers. Apply herbicides around mid-September before frost.
  • September is the best month for seeding new lawns or reseeding bare patches in existing lawns. Seeding should be completed by September 15 or 20 so grass germinates and establishes before winter.

Trees and shrubs

  • September is a great month for adding woody plants to the landscape. Fall root growth gives them a head start versus waiting until next spring.
  • During fall dry spells, soak trees and shrubs every seven to ten days if rain is lacking. Evergreens are more resistant to winter injury if they receive weekly moisture throughout late summer and autumn, rather than the old rule of merely soaking the soil before freeze up.
  • Major pruning should wait until early next spring before leaf-out. Wounds heal slowly in fall, leaving cut twigs open to winter injury. Light trimming is fine.

Flower garden

  • September is the month to divide or relocate peony, daylily, true lily and bleeding heart. August is best for iris, but September works also. Always water well immediately after replanting.
  • Bulbs, corms and roots that don’t survive winter 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 produce new roots this fall.
  • Collect seeds of non-hybrid annuals like four o’clock, cleome, marigold, sweet pea, nasturtium and zinnia when flower heads are dry and ready to shatter.

Vegetable garden

  • Rhubarb can be divided or moved now. 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.
  • To develop a new garden spot for next year where lawn exists, skip a mowing then spray with Roundup. Rototill after about two weeks.

Geraniums and coleus

  • Cuttings rooted in September can be grown indoors as houseplants all winter and planted outdoors next spring. Root four-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 four or five inch diameter pots when they’re rooted in two or three weeks.

Happy September Gardening!