With the advent of September and autumn, the cooler nights are a time to give yourself a brief respite after the summer and refresh your vegetable garden with a cover crop. Cover crops, also called green manure, are very beneficial to the “tilth” (structure, or physical suitability for planting) of your soil. Sown in the fall, usually late September, cover crops will enhance soil over the winter. They attract pollinating insects, break up heavy soil, add organic material and decrease the number of weeds.