Continue to harvest. Winter squash is ripe when the ground spot turns from white to a cream or gold color. Potatoes are ready when tops die down. Store in a dark location.
Mulch carrots, parsnips, and beets for winter harvesting.
Protect tomatoes or pick green tomatoes if frost threatens.
Begin reducing water on trees, shrubs, and vines to harden them off for winter.
Mulch trees and shrubs with wood chips, ground bark, or fall leaves to protect and nourish the soil.
September is a good time to plant new trees and shrubs for healthy root growth over winter.
Plant or transplant woody ornamentals and established herbaceous perennials.
September is the best time to fertilize lawns for strong roots. Use an organic or slow-release fertilizer that rain wonâ€™t wash away.
Improve poor lawns with a fall round of core aerating, reseeding, and top-dressing with Â¼ inch of compost before October 15.
Lawns seeded by early October will grow strong roots to survive next summerâ€™s weather.
Plant hardy spring-flowering bulbs such as daffodils, tulips, and crocus; add bulb fertilizer and be sure to water them before the ground freezes. Select big, hearty-size bulbs.
Stake tall flowers to prevent them from wind damage.
Dig, clean, and store tuberous begonias if frost threatens.
Divide peonies and iris.
Keep checking your plants for diseases and insects, and treat them when necessary. Slugs are often still a problem and need to be baited or removed.
Bring your houseplants outside to clean, fertilize, and repot them, then bring them indoors for the winter.
Once the weather gets cooler, dig and divide your perennial plants and herbs.
Do a final weeding before winter and clean up any debris from your garden and lawn to avoid disease come spring.
Mix organic materials into your soil before the ground freezes.
Donâ€™t forget to turn your compost pile to quicken decomposition! Compost piles need air.