Vegetables can still be productive for a couple more months depending on what crops you have been growing. Certainly long season crops like tomatoes, peppers, Swiss chard are there now and will continue to produce till frost for the tender vegetables and Chard will tolerate quite a bit of cool or cold weather. Root crops like turnips, carrots, beets, parsnips, potatoes and onions can be harvested anytime they are ready and into frosty weather. If you mulch the rows with straw and prevent freezing, root crops could be harvested even with snow cover. If you got your cabbage transplants in earlier then will be ready a bit later too.
A trend in vegetables the past couple of seasons has been the idea of growing greens and harvesting them while they are very small and tender. So our calendar may not allow us to grow lettuces, greens and spinach to their mature sizes, yet we can certainly harvest them as whole smaller plants for fresh table use in salads and garnish for other dishes as well.
Since many of our vegetable plants were not producing fruits because of the high day and nighttime temperatures even if you watered, you can experiment with season extenders to get a bit farther into fall and not have the weather put an end to your gardening experience. These can be as simple as protecting from the earliest of frosts by covering tender plants with an old bed sheet or light blanket. More involved will be a temporary structure created over the rows or setting the cold frame you used in the spring to harden off your plants over a portion of a row or rows. Most anything you used in the spring to protect your vegetables from the late frosts can be reused to protect from the early fall frosts. It seems a bit odd to add this last part in a column in August, but if you have valuable produce close to being mature enough to harvest, be prepared to harvest if you cannot protect the plants so the fruit is not damaged by the cold weather.
What you do not want to allow is the weeds to go to seed in areas that you have already harvested all your vegetables. This will set you up for a weed problem next year. Since most gardeners do not have a "hot" composting system, those weed seed heads should be thrown out and not put in the compost bin. We have all had tomato plants show up in beds where we used our own compost as organic matter for example. If you have enough of an open area, consider sowing a cover crop to help condition the soil and keep the weed population down. You can turn them in late this fall or leave them as winter cover if you like. If you routinely turn in all your plant parts each year, don't turn in diseased plants that will provide disease inoculum for next year. Gardeners who mow, mulch and bag their tree leaves also have the option of using those in the garden as well, turning them in alone or with other kinds or organic matter.
About the author: Richard Hentschel’s expertise extends across several subject areas with specialties in lawn care, fruit tree production, woody ornamentals, and home and community gardening. During his 45-year career in horticulture and agriculture, Hentschel became a well-known and respected expert for commercial and homeowner audiences, industry organizations, and media. He retired from University of Illinois Extension in April 2022 with nearly 30 years of service as a Horticulture Specialist and Educator in northern Illinois.