September Garden Calendar

Plant Clinics

Some plant clinics at Farmers Markets will operate until October. For schedules and locations visit the Plant Clinics page on this website.

Trees & Shrubs

If weather remains hot and dry, water deeply any trees or shrubs that have been planted within the past year.

September is a good time to plant shrubs and trees. If you are planting a containerized shrub or tree, carefully inspect the roots. Prune out circling roots or those that have started to grow upward in the pot. Remove as much of the planting medium from the roots as possible either by hand or using a hose. Tease out the roots so that they are pointing outward. Dig a hole that is at least twice as wide as the diameter of the root ball, and make sure the root flare of the trunk is at or a little above the final level of the backfilled soil. Do not amend the backfill soil. Water it well and continue regular watering throughout the fall.

Do not fertilize your trees and shrubs now. This can produce tender growth that is not hardy during winter cold. For deciduous trees, wait until they go into dormancy before fertilizing.

Prune all dead, damaged or diseased branches any time of the year. Other pruning of trees and shrubs should wait until cooler weather in November and beyond.

Annuals, Perennials

Remove spent flowers of cosmos, zinnia, marigold, scabiosa and others to maintain vitality of the plants and keep them flowering. Resist the temptation to cut back perennials that are beginning to show the rigors of the long hot summer. Allow the plant to distribute sugar reserves from the leaves and stems to the roots, crowns or tubers in preparation for winter.

Inspect your perennials. Remove diseased plants and those that are overcrowded.


Three inches or higher is a good cutting height for Kentucky bluegrass, perennial ryegrass and tall fescue.Mow zoysiagrass and bermudagrass to 1 to 2 inches.Use a mulching mower, and leave the clippings on the lawn to return nutrients to the soil.Cool Season Grasses
September is great time to plant grass. See our feature Lawn Renovation, Part 1: Making Choices and Lawn Renovation, Part 2: Planting Grass.September is the beginning of lawn fertilization