September Garden Calendar
How to Set Multiple Traps to Catch the Spotted Drosophila Fly
How to Make a Trap to Catch the Spotted Wing Drosophila Fly
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The monthly gardening calendars are produced by OSU Extension. Each calendar provides reminders of key garden chores, such as fertilizing, pest control, planting, and maintenance.

Recommendations in this calendar are not necessarily applicable to all areas of Oregon. For more information, contact your local Extension office.

Sustainable gardening

Oregon State University Extension Service encourages sustainable gardening practices.

Preventative pest management is emphasized over reactive pest control. Identify and monitor problems before acting, and opt for the least toxic approach that will remedy the problem.

  • First consider cultural, and then physical controls. The conservation of biological control agents (predators, parasitoids) should be favored over the purchase and release of biological controls.
  • Use chemical controls only when necessary, only after identifying a pest problem, and only after thoroughly reading the pesticide label. Least-toxic choices include insecticidal soaps, horticultural oils, botanical insecticides, organic and synthetic pesticides — when used judiciously.

Maintenance and Clean Up

  • Dampwood termites begin flying late this month. Make sure your home is free of wet wood or places where wood and soil are in contact.

  • Harvest winter squash when the "ground spot" changes from white to a cream or gold color.

  • Pick and store winter squash; mulch carrot, parsnip, and beets for winter harvesting.

  • Protect tomatoes and/or pick green tomatoes and ripen indoors if frost threatens.

  • Reduce water on trees, shrubs, and vines east of Cascades to harden them off for winter.

  • Stake tall flowers to keep them from blowing over in fall winds.

  • Dig, clean, and store tuberous begonias if frost threatens.

  • Harvest potatoes when the tops die down. Store them in a dark location.

  • Optimal time for establishing a new lawn is August through Mid-September.

  • Aerate lawns.

  • Early-September: apply 1 lb. nitrogen per 1,000 sq.ft. to lawns. Reduce risks of run-off into local waterways by not fertilizing just prior to rain, and not over-irrigating so that water runs off of lawn and onto sidewalk or street.

  • Willamette Valley: stop irrigating your lawn after Labor Day to suppress European crane fly populations.

  • Recycle disease-free plant material and kitchen vegetable and fruit scraps into compost. Don't compost diseased plants unless you are using the "hot compost" method (120° to 150°F).

Planting/Propagation

  • Divide peonies and iris.

  • Plant or transplant woody ornamentals and mature herbaceous perennials. Fall planting of trees, shrubs and perennials can encourage healthy root growth over the winter.

  • Plant daffodils, tulips, and crocus for spring bloom. Work calcium and phosphorus into the soil below the bulbs at planting time. Remember when purchasing bulbs, the size of the bulb is directly correlated to the size of the flower yet to come in spring.

  • Western Oregon: plant winter cover of annual rye or winter peas in vegetable garden.

Pest Monitoring and Management

  • Apply parasitic nematodes to moist soil beneath rhododendrons and azaleas that show root weevil damage (notched leaves).

  • Control slugs as necessary. Least toxic management options for slugs include barriers and traps. Baits are also available for slug control; iron phosphate baits are safe to use around pets. Read and follow all label directions prior to using baits, or any other chemical control.

  • Monitor trailing berries for leaf and cane spot. Treat if necessary.

  • As necessary, apply copper spray for peach and cherry trees.

  • Spray for juniper twig blight, as necessary, after pruning away dead and infected twigs.

  • Continue monitoring late-season soft fruits and berries for Spotted Wing Drosophila (SWD).  If SWD are present, use an integrated and least toxic approach to manage the pests.  Learn how to monitor for SWD flies and larval infestations in fruit.

  • Coastal and western valleys: spray susceptible varieties of potatoes and tomatoes for early and late blight.

Houseplants and Indoor Gardening

  • Clean houseplants, check for insects, and repot and fertilize if necessary; then bring them indoors.

Download the September Calendar (PDF - 111.15 KB)

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