August is a transitional period for gardeners, marking the start of the “second season” for planting. Sowing seeds now, despite the intense summer heat, is necessary to ensure a productive harvest once cooler autumn temperatures arrive. This practice, known as fall gardening, allows for the cultivation of crops that thrive in moderate weather and often taste sweeter after a light frost. Success requires careful planning, selecting suitable varieties, and managing the remaining heat.
Seeds for Fall Harvest
The primary seeds suitable for August planting are cool-season crops that prefer to mature as temperatures drop. These vegetables are generally frost-tolerant and develop a better flavor profile when exposed to a light chill. Cultivating these crops now maximizes garden space for a continuous food supply.
Root vegetables are a dependable choice for a fall harvest, as their underground storage organs sweeten in the cold. Carrots typically take around 60 days from seed to harvest. Beets are an excellent option, with seeds able to germinate in soil temperatures up to 90°F. Turnips also mature quickly, often ready in about eight weeks, allowing for the harvest of both roots and greens.
Brassicas, or cole crops, constitute another significant category for August sowing. Kale and collard greens are particularly frost-hardy, requiring about 6 to 8 weeks to reach maturity. Cabbage and broccoli can also be planted, but it is best to select faster-maturing varieties or rely on transplants if the growing season is short.
Leafy greens are popular for fall planting due to their fast growth and preference for cooler conditions. Spinach and lettuce thrive in autumn, though their seeds struggle to germinate if soil temperatures remain above the mid-70s Fahrenheit. Swiss chard is a resilient alternative that tolerates both light frost and summer heat, with baby greens ready in four weeks. Other greens like arugula and Chinese greens, such as pak choi, also benefit from the cooler weather.
Quick-Maturing Crops for Late Summer
A secondary set of seeds can be planted in August, focusing on varieties with a short “Days to Maturity” (DTM) that allow for harvest before the first hard frost. These crops generally mature in 30 to 60 days. Radishes are the fastest option, often going from seed to harvest in just one month, making them suitable for succession planting throughout late summer.
Bush beans represent the last practical sowing date in early August for many regions, as they mature faster than pole varieties. Peas, specifically green or sugar peas, can also be sown now for a moderate fall yield, as they tolerate cold better than beans. However, these crops are more sensitive to a hard frost than dedicated cool-season vegetables.
Certain herbs also perform better when sown in August, particularly those that struggle in intense summer heat. Cilantro is an excellent example, as it bolts quickly in hot weather but thrives once temperatures cool, providing a harvestable crop in just a few weeks. Dill, parsley, and chives will also benefit from the moderate conditions of autumn.
Calculating Timing Based on First Frost
Accurate timing is paramount for a successful fall harvest, requiring calculation backward from the expected first frost. The average First Frost Date (FFD) is the guiding metric, representing the typical day temperatures dip below 32°F. This date is an estimate based on historical weather data for a specific location and is often available through local extension offices or online calculators.
Gardeners must consult the “Days to Maturity” (DTM) listed on the seed packet, which indicates the time from seeding to harvest. The planting date is determined by subtracting the DTM from the FFD. For example, if a crop takes 60 days to mature and the FFD is October 30, the latest planting date is August 31.
It is necessary to account for the slower growth rate that occurs as days shorten and the sun’s intensity decreases in autumn. To compensate for this reduction, it is advisable to add a buffer of 10 to 14 days to the stated DTM. This adjustment ensures the crop reaches a harvestable size before the cold weather sets in permanently. This calculation allows for strategic planting, ensuring frost-sensitive plants are harvested before the FFD.
Essential Techniques for Late Summer Sowing
Sowing seeds in August presents the challenge of high soil and air temperatures, which inhibit the germination of cool-season crops. The initial focus must be on managing the heat and maintaining consistent soil moisture. Watering the soil thoroughly before planting helps pre-moisten the area, slightly cooling the ground and preventing a hard, dry crust from forming.
Providing temporary shade is an effective strategy to encourage germination in hot conditions. Shade cloth, row covers, or intercropping with taller plants can filter the intense sun, protecting tender emerging seedlings from scorching. For seeds that struggle with heat-induced dormancy, such as lettuce and spinach, a light layer of straw mulch helps keep the soil surface cool and traps moisture.
Consistent moisture management is necessary; hot soil dries out quickly, requiring the gardener to check the seedbed multiple times a day. Watering should be done in the evening or early morning to allow moisture to penetrate deeply before rapid evaporation occurs. Planting seeds slightly deeper than usual can also help them access cooler, moister soil layers.
Preparing the soil with amendments supports the rapid growth required for a fall harvest. Applying compost ensures the second crop has the necessary nutrients for development. Since germination rates are unpredictable in the heat, planting extra seeds is a good practice. Aggressive thinning must follow promptly once seedlings appear to prevent competition for water and nutrients.