Fall Vegetable Garden
As the summer vegetable crops reach maturity, August and September are an ideal time to plant cool-season crops for an autumn full of homegrown produce. Cool-season crops are those that tend to perform poorly in summer heat, but thrive in the cooler months. Many ‘bolt’ (flower) in warmer seasons, causing the leaves and roots we consume to taste bitter and fibrous. The primary challenge in growing cool season crops in the fall is to ensure they are ready to harvest before the average first killing frost, which in our area tends to be in late October. To determine when to plant a given vegetable for the latest harvest, consider the typical time to maturity for a particular variety and the length of the harvests period, and count backwards from the average first frost date. Carrots, for example, take about 70-80 days from seed to reach harvestable maturity, so carrots can be direct seeded in August. Leafy greens and turnips, on the other hand, reach maturity in about 50-60 days, so they can be planted as late as September. Other crops like green onions, collards, and kale, will still produce through winter. For a complete planting calendar, visit:
To prepare the planting site, start by removing weeds and warm-season crop residues. If you fertilized heavily in the spring, there may be sufficient nutrients in the soil for leafy vegetable crops, otherwise it is best to incorporate 2-3 inches of compost, or fertilize according to soil-test recommendations. Most fall vegetables perform better with supplemental nitrogen application three to six weeks after planting.
The summer heat requires adjusting your seed planting technique, as soil high temperatures can inhibit germination and increase water stress on seedlings. Lettuce and spinach seeds, in fact, typically won’t germinate if soil temperatures are above 85º F. Soil temperatures are higher and soil moisture levels are lower towards the surface, so it is better to plant seeds one-and-a-half to twice as deep as you would in spring to avoid temperature and moisture stress. After planting seeds, you may add a thin layer of mulch, or cover with burlap or newspaper to reduce the heat load, but remove immediately after germination. Be sure seedlings remain well watered, as they are particularly vulnerable to desiccation. Larger transplants grown from seed or transplants from garden centers may better withstand summer heat than seedlings directly seeded into the vegetable bed. Maturing vegetables need the equivalent of about one inch of water per week, either by rain or irrigation. Watering deeply, if less frequently, favors deeper root development.
Matt Jones is Horticulture Agent for North Carolina Cooperative Extension in Chatham County.