September Gardening Activities - Region 5

Gardening Tips for September

Rocky Mountain and California Mountain Gardens

Learn2Grow Region 5 Map

States in the region:

Utah, Colorado, Wyoming, Idaho, California (Mountains)

Key Issues for September

  • Powdery mildew can be troublesome in the late summer garden. At this point in the growing season, it's too late to treat with a fungicide. Garden cleanup will be key this fall; all infected plants should be bagged and thrown away.
  • Get ready for grub season. These young beetle larvae aggressively feed on the roots of lawn grasses. Late summer through early fall is the ideal time to control large grub populations. (Note: It's when you see 10 or more grubs per square foot that you need to treat your lawn. As always, be sure to carefully read and follow all insecticide label directions for proper, safe use.)
  • Stay on the lookout for stinging insects! Bees, wasps and hornets still make their ugly presence known this time of the year.
  • Buy your bulbs early! Remember all those daffodils that you admired in your neighbor's garden this past spring? Experienced gardeners buy their spring-flowering bulbs - like daffodils, tulips, crocus and hyacinths - now. Avoid having a disappointing selection by buying what you want now, while the selection is good. Not sure how to pick the best bulbs? Select ones that are firm, not soft or mushy.
  • Plant hardy chrysanthemums in the garden. "Hardy" means just that: They'll return each spring with new growth and flower in the fall.
  • Continue to harvest your homegrown vegetables as they ripen. Store extra produce for future enjoyment, or donate it to a local soup kitchen or food pantry.
  • Rework or expand your perennial border by dividing summer-flowering perennial clumps that are now going to seed. (Don't touch the flowering asters, mums or ornamental grasses until early spring, though.)
  • Use up any extra tomatoes the delicious way: Make an easy, fresh and nutritious batch of homemade bruschetta!
  • Keep deadheading roses to keep those new blooms coming, but stop deadheading at the end of the month so they'll start to slow down. As tempted as you might be, don't feed your rosebushes anymore this season. Fertilizing them now will stimulate new growth that won't harden off before winter. (And it'll soon be time to prepare your roses for their upcoming winter's nap.)
  • Water and fertilize the lawn to strengthen its roots for the months ahead, always carefully following package directions. After the heat stresses of the past two months and very limited rainfall in some areas, turfgrass needs a little boost to get it through the winter.
  • Prepare your outdoor-summering houseplants for their return indoors. Before you bring houseplants back inside, do a careful inspection of each one so you don't bring any unwanted multi-legged pests inside your home!
  • Create new interest in your perennial garden with ornamental grasses for fall. Color, texture and sound are a few of the wonderful attributes that grasses bring to the landscape. The show won't end in fall either - grasses continue their attraction during the gray winter months by adding color and winter respite for small wildlife.
  • Retire your tired-looking, heat-exhausted summer plants to the compost pile (without any guilt). They've served you and your garden well, but now it's time to bring back the pizzazz with fall-loving beauties like pansies, ornamental cabbage, kale and snapdragons! These cool-weather annuals (and more) are naturals for fall-themed containers, as well as in landscape beds and borders.
  • Put your pruning shears and hand pruners away for the year. Unless you see a dead branch, do not do any pruning, because any new sprouting growth that follows will be particularly tender to upcoming frosts. When you know when to prune, your garden will look its best!
  • Pay close attention to the weather forecasts for predictions of early frosts, and be prepared to adjust your gardening practices accordingly. The typical first frost of the season is an average date - it could be surprisingly earlier or even later. Don't get caught with your plants down! Harvest your remaining produce and protect tender plants before that first frost hits.
  • Do some late-season assessment of your garden and all container plantings. If you keep a garden journal (and you should), make notations on what worked and what didn't, so you'll be even more prepared next year. Remember, a picture's worth a thousand words - grab the camera and capture the good (and the bad) in your garden!
  • Come to The Garden Party and share your gardening adventures and ideas with other green thumbs in your region, as well as nationwide. Post pictures of your garden, write a blog, or ask expert gardeners for more help, tips or suggestions on how to enhance your outdoor living experience.