Many yards and gardens this spring had winter annual weeds such as henbit, deadnettle, and common chickweed. Winter annuals germinate from seed in the fall and spent the winter as seedlings. If you had a problem with winter annuals this year, fall is the best time to control them.
If you are comfortable using chemicals, consider applying a preemergence herbicide this fall before these plants germinate again. This is best done in September. The recommended chemical will vary depending on where the weeds are located. For many flower gardens, Preen is a good option. When using any chemical pest control, be sure to read, understand, and follow the label directions for proper use.
If you prefer to use manual control options, watch for the winter annual weeds to germinate in late September or early October. All plants are easiest to control when they are small. Simply hand pull, hoe, or rake the weeds out. Try not to disturb bare soil surfaces too much because that will bring up additional weed seeds to the soil surface.
Fall is also a good time to control some more difficult weeds in the landscape. For example, Creeping Charlie, dandelion, white clover, and many thistles are easier to control with chemical applications in the fall. These are herbaceous perennial plants, meaning that they live from year to year from the same root structures, but above-ground growth dies back each fall. As the plant moves its food and energy to its roots to overwinter, it will move systemic chemicals with it to kill the entire plant.
Finally, spend some time this fall doing general garden cleanup. Remove debris and weed growth from among your landscape beds and in spent vegetable gardens. Take notes of which weeds are most prevalent. For example, if you have a lot of crabgrass (also called water grass), consider using a preemergence herbicide in the spring that will control kill the crabgrass seed before it germinates in your garden.
Make note if your gardens had excessive weed growth in bare soil areas. Bare soil areas often produce more weeds. Consider planting more perennial flowers or shrubs to cover the area and out-compete the weeds. Add two to four inches of mulch to reduce weed growth in bare soil areas by keeping weed seeds in the dark and smothering small-seeded annuals as they germinate.
Want to learn more? Michelle Wiesbrook, Weed Science Specialist, discusses various types of weed control methods in a free taped webinar on the University of Illinois Extension Horticulture YouTube channel.