September Gardening on the Western Slope of Colorado

 September Garden Calendar

Adapted from:
Patrick Miller
Colorado State University Extension Master Gardener in Larimer County
September 26, 2015

For Colorado gardeners August means, “Get ready for fall!” The Autumnal Equinox falls on September 22 this year, signaling approximately equal hours of daylight and darkness. Shortened day length and lower temperatures signal plants to slow-down or halt growth. Even now, plants are going through the process of getting ready for winter!

The gardening season is far from over, and below are just a few tips for gardeners to get their plants ready for this fall and beyond.
  • This is a great time to plant new trees and shrubs because the new roots will have plenty of time to become established before the spring.
  • Fall is the best time to fertilize your lawn. Be sure to fertilize before the end of October.
  • Fertilize all budding, blooming, flowering and fruiting plants for a maximum fall harvest and show of colour.
  • Bring summer vacationing houseplants back indoors while the windows are still open; check carefully for hitchhiking pests.
  • Start fall clean-up in the flower beds, cutting back anything that has finished blooming or is diseased.
  • Take cuttings to overwinter indoors.
  • Watch for frost warning and cover tender plants.
  • Blow out your sprinkler system prior to a hard freeze.
Flowers and Other Ornamental Plants:
  • Plant roses and other flowering perennials to give them time to become established before the spring.
  • Divide and move perennials.
  • Dig and store tender bulbs like: dahlias, caladiums, cannas and tuberous begonias.
  • Plant spring flowering bulbs and peonies.

For more gardening tips, most visit the Colorado State University Extension website at for additional suggestions and topics specific for our region.

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