August is the time for harvesting and enjoying the summer’s bounty in the vegetable garden while thinking ahead to a winter’s garden. Even though it is hot and humid, planting carrots, green onions (scallions), and cole crops such as cauliflower, broccoli, broccoli raab, Brussels sprouts, cabbage, and collards will give great yields in cold months. Later or by September, also consider planting spinach, Swiss chard, radish, turnip, and Asian or hardy greens such as mustard, tatsoi, mache, and kale. You still have time to plant garlic: that’s in October.
To determine when to plant look at the “days to maturity” on the seed packet. Count backwards from the average first frost date (Halloween in Northern Virginia) to determine when to plant. But the difference between fall and spring planting is the “Short Day” factor, which may not be addressed on the seed packet. If you are going to plant seed, you have to add 2 weeks to the numbers on the seed packet to allow for the cooler night temperatures and the shorter day lengths. For example, to sow spinach seeds add the 7 to 10 days for germination, 35 days to reach maturation, and 14 days for the Short Day factor for a total of 56 to 59 days. Therefore, the latest one can sow spinach seeds is the beginning of September. The length of time would be shorter if nursery transplants were used instead of seed because they have a head start.
Also, find out the best temperature range for seed germination (start indoors versus outdoors), keep the seeds moist during dry times in the summer, and get to know each crop’s tolerance for cold (soil and air) to know if you should provide additional warmth with row covers.
Virginia Cooperative Extension
Vegetable Planting Guide and Recommended Dates #426-331
University of Maryland Extension
Planting Dates for Vegetable Crops in Maryland #HG16
Vegetable Planting Calendar for Central Maryland #GE-007
Southern Exposure Seed Exchange
Southern Exposure Seed Exchange is a Virginia-based seed company that also has very useful local information:
Fall and Winter Quick Reference