You have diligently howed, mowed, pulled, sprayed, and, dug weeds in your garden all summer, and now that you have harvested the crops, you deserve to put your feet up and rest a little, right? Right. But now is not the time, when it comes to garden weeds. Fall is the time when many weeds make tremendous gains in root growth and seed production. To lower your guard now will be a mistake you will pay for years to come. The seeds of annual weeds such as pigweed will be viable for up to 40 years, and many thousands of them can be produced before winter. Perennial weeds such as Canada thistle can produce dozens of yards of new roots that are covered with vegetative root buds, each capable of producing a new, independent plant. So wait a little longer to let up on your weed control efforts.
In the garden plot accomplish two objectives by covering the plot with a winter mulch; weed control and soil protection. Soil exposed to sunlight and weather loses its organic matter, becomes compacted, or can be lost to wind and water erosion. To use a winter mulch, till the soil, add one inch of finished compost, and cover with a heavy black plastic mulch. Weight the plastic down well to prevent winter winds from blowing it. Any tough perennial weeds that penetrate the mulch can be easily sprayed with a glyphosate herbicide, such as Roundup, that will move down into the root system to kill the plant. Most weeds, except quackgrass and field bindweed, are not tough enough to penetrate the plastic. The plastic should still be pliable enough to remove in the spring. A disadvantage of plastic mulch is it will not allow the oxygen exchange that healthy soil needs.
There are several alternatives to plastic mulch, such as straw, lawn clippings, or hay. If you live in a windy area, loose mulches can be held in place in winter by staking chicken wire over them. Select weed-seed-free materials to use as mulch. Another alternative used successfully by some gardeners is the fall planting of a cover crop such as a legume, grass or winter rye, thickly sown to crowd out weeds, and left in place through the winter. If you select a legume cover crop, such as Austrian peas, there is the added advantage of the nitrogen the legume adds to the soil. Till the cover crop under in the spring, which will add organic matter to your soil.
For more information, see the fact sheet in this series "Late Summer Weed Management".
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