Man Next To Wheelbarrow Full Of Garden Fruits And Vegetables
sept pnw
(Image credit: JackF)

It’s September in the Northwest and the beginning of the fall gardening season. Temps are getting cooler and higher elevations may see frost by the end of the month, while gardeners west of the mountains can enjoy a few more weeks of mild weather. You’ve been working since early spring, but don’t stop your September gardening tasks quite yet; there is still plenty of Northwest garden maintenance yet to be done.

September Gardening Tasks

Here are a few suggestions for your autumn gardening to-do list:

  • September is an ideal time to plant new trees and shrubs. The soil is still warm and roots have time to establish before freezing weather arrives. However, it’s wise to wait a couple of weeks if the weather is still hot in your region.
  • September in the Northwest is a great time to add new perennials or to fill empty spots in your garden beds. Your gardening to-do list for autumn should include planting tulips, crocus, daffodils, and other spring bulbs. Gardeners in milder climates can plant bulbs until early December, but those in higher elevations should get bulbs in the ground a few weeks earlier.
  • Gardeners east of the Cascades should gradually decrease watering vines, trees, and shrubs to harden them before the arrival of winter. Avoid watering in the evening as days get shorter and temperatures drop. Areas west of the mountains may see the beginning of fall rains by now.
  • Harvest pumpkins and other winter squash as soon as the rind is hard and the spot touching the ground turns from white to creamy yellow or gold, but before temps drop to 28 degrees F. (-2 C.). Winter squash stores well but be sure to leave about 2 inches (5 cm.) of stem intact.
  • Dig potatoes when the tops die down. Set the potatoes aside until the skins toughen, then store them in a cool, dark, and well-ventilated location.
  • Harvest onions when the tops fall over, then set them aside in a dry, shady place for about a week. Trim the leaves to about an inch (2.5 cm.), then store firm, healthy onions in a cool, dark location. Set aside less-than-perfect onions and use them soon.
  • Northwest garden maintenance also includes ongoing weed control. Continue to hoe, pull, or dig pesky weeds and don’t be tempted to stop weeding too soon. At the very least, prevent weeds next spring by mowing or cutting off seed heads.
  • Feed annuals one last time and give them a light trim for a few more weeks of blooms. In cooler climates, pull spent annuals and toss them on the compost pile, but don’t compost diseased plants.
Mary H. Dyer

A Credentialed Garden Writer, Mary H. Dyer was with Gardening Know How in the very beginning, publishing articles as early as 2007.