A fall garden is an opportunity to extend the harvest season by planting new crops in mid-to-late summer for maturity in autumn and early winter. This second planting season takes advantage of cooler temperatures and often less intense pest pressure compared to the summer months. Successful fall gardening yields vegetables with noticeably improved flavor, where starches within the plant convert to sugars after exposure to light frost. This shift in flavor is particularly evident in root vegetables and certain leafy greens. Planting now ensures a continuous supply of fresh produce well after the summer heat has passed.
Calculating Planting Dates for a Fall Harvest
The primary challenge for a successful fall garden is timing the planting correctly so crops mature before a killing frost arrives. Unlike spring gardening, which calculates forward from the last expected frost, fall planting requires calculating backward from the average first frost date in your specific area.
Once the expected first frost date is determined, you must use the “Days to Maturity” (DTM) listed on your seed packet. This DTM figure is based on optimal growing conditions, which are not present in the fall. Plant growth naturally slows as daylight hours decrease, requiring an adjustment to the planting schedule.
To account for this slower growth rate, a “fall factor” must be added to the crop’s standard DTM, typically ranging from 10 to 14 days. The total number of days to count back from your average first frost date is the DTM plus this fall factor. For crops that are not frost-tolerant, an additional buffer of about two weeks is wise to ensure a harvest before the cold arrives.
Recommended Cool-Season Crops
Selecting the right vegetables for a fall garden involves focusing on crops that thrive in cooler temperatures and can tolerate light frost. These cool-season vegetables are organized into three main categories based on their growth habit and cold hardiness. Success relies on choosing varieties with shorter DTMs, ensuring they reach maturity before the deep cold sets in.
Leafy Greens
Leafy greens thrive in the fall garden, as cooler air prevents them from bolting, or prematurely going to seed, which often happens in summer heat. Spinach is highly cold-tolerant and will produce tender leaves well into the season, surviving a few frosts. Kale is another excellent choice, with its flavor improving significantly after a light frost.
For fast harvests, consider succession-planting every few weeks for a continuous supply. Greens that offer quick growth and resist bolting in cooling temperatures include:
- Loose-leaf lettuce varieties
- Arugula
- Swiss chard
- Bok Choy
These greens should be planted in mid-to-late summer to ensure they are established before daylight hours become too short.
Root Vegetables
Root vegetables are ideal fall crops because they mature underground and their flavor is enhanced by cold temperatures. Common choices include:
- Carrots, which become sweeter when they mature in cool soil and can be left in the ground for storage.
- Beets, which also tolerate being left in the ground past the first frost.
- Radishes, which are exceptionally fast, often ready to harvest in 3 to 4 weeks.
- Turnips, a sturdy crop providing a dual harvest of both root and leafy greens.
For all root crops, the soil must be prepared deeply and be free of stones or hard clumps to allow for straight, unimpeded growth.
Brassicas
The Brassica family, also known as cole crops, prefers cool weather to form their edible parts. Key members include:
- Broccoli
- Cabbage
- Brussels Sprouts
- Cauliflower
Broccoli and Cauliflower produce the best heads when they mature during the crisp temperatures of autumn. These vegetables are slower-growing and are often best planted as transplants in mid-summer to give them enough time to size up.
Brussels sprouts require the longest growing season but are incredibly cold-hardy, with their flavor sweetening after a frost. When planting brassicas, select varieties labeled as “early” or “short-season” to maximize the chance of a successful harvest before the hard freeze.
Preparing the Garden Beds
Preparing the garden beds for fall planting involves swift action once the summer crops have finished their cycle. The first step is to clear the area, removing all spent plant material and lingering weeds to prevent disease and pest carryover.
Next, the soil should be refreshed by incorporating new organic material to support the rapid growth required for a fall harvest. Working in a layer of well-aged compost or manure replenishes nutrients and improves soil structure. A light application of a balanced granular fertilizer can be incorporated into the top 6 to 8 inches of soil, especially if previous summer crops were heavily fertilized.
In the heat of mid-summer, soil temperatures can be too high for the germination of many cool-season seeds like lettuce and spinach. Shading the prepared bed with a row cover or cardboard for a few days before planting can help cool the soil surface. A light top dressing of vermiculite or compost over the sown seeds can also help retain moisture and prevent a hard crust from forming, which can hinder delicate seedlings.
Season Extension Techniques
Once fall crops are established, season extension techniques become necessary to protect them from early and sustained cold, effectively stretching the harvest window. The goal is to create a microclimate that traps warmth and insulates the plants from freezing temperatures.
Lightweight row covers consist of fabric draped directly over the plants or supported by wire hoops. This fabric allows light and water to pass through while trapping heat, raising the temperature surrounding the plants by about 4°F. This is often enough to protect against a light frost. Row covers also act as a physical barrier against late-season insect pests.
Cold frames offer a more durable solution, acting as miniature greenhouses particularly effective for leafy greens. These structures are boxes with clear, hinged lids made of glass or plastic that collect solar energy to warm the interior. Managing the temperature is important, requiring the lid to be propped open, or vented, on sunny days to prevent overheating.
For root crops, heavy organic mulch is the preferred method of protection and storage. A deep layer of straw or shredded leaves placed over the row insulates the ground, preventing the soil from freezing solid. This allows gardeners to harvest root vegetables like carrots and beets on an as-needed basis, even after the air temperature has dropped well below freezing.