When to Begin Fall Seed-Starting: Tips for Your Zone
We may be in the heart of summer, growing and harvesting, but it’s not too early to begin planning or even starting some of our favorite fall seeds. From blooms to vegetables, with direct sowing or starting indoors, garden expert Katherine Rowe outlines when to begin fall seed starting for your growing zone.
Contents
Summer brings the best garden yields, from flowers to herbs to vegetables, but we can’t help but get excited about the fall harvest around the corner. Cool weather and a bounty of hardy crops and autumnal blooms begin with planning now. Depending on your growing zone, the time to start seed-starting is now or in the near future.
For gardeners in mild climates with long growing seasons, mid-summer allows time to sow a successional round of crops like cucumber, beans, basil, and even tomatoes. Get those fast-growing winter squashes and pumpkins in the ground now for a late reward before the first anticipated fall frost. In areas with shorter growing seasons, the focus shifts to sowing for the fall harvest and floral show.
Whether sowing to reap the flavor of fall before frost or establish hardy selections to grow over the cool season, we’ll look at when to start fall seeds for your zone. By balancing the transition from the heat of summer to cooler conditions, we’ll have the best foundation for healthy development.
Zeolights Calendula (Pot Marigold)
Zeolights Calendula (Pot Marigold) Seeds
Timing the Seed-Starting
It can be tricky to time seed-starting just right when we’re faced with hot, dry temperatures in late summer moving into cool, damp conditions of early fall. Three factors help determine our timing: growing zone, fall’s first anticipated frost date, and the length of time it takes our selections to mature. For frost-sensitive crops, we need to act before frost sets in to fully enjoy the yield. For frost-hardy plants, we’ll want to wait until summer heat passes to give seedlings the cool conditions they need to thrive.
The good news is that seeds germinate well in warm (not overly hot) conditions. Seedlings will get off to a head start in late summer for earlier development and production in fall. To start seeds with plenty of time to develop but to avoid wilt in intense end-of-summer heat, consider starting them indoors in a warm, bright location. Or, place trays outside where they receive afternoon shade protection to avoid burning.
First Frost Date
An essential tool in planning when to start fall seeds is knowing your area’s first anticipated frost date. This is an estimate based on climate data that provides a scope of when heavy frost is likely. It doesn’t account for your microclimate or specific site conditions, but it is useful in determining when to sow.
Many cool-season selections enjoy chilly conditions that lead up to the first frost, and frost-tolerant crops even sweeten with the nip. Frost-tender crops need harvesting before the frost arrives. With many taking six to eight weeks to mature from seed, starting in late summer is best to enjoy the rewards before icy dieback. Consider crop covers or a cold frame to extend the season in cool weather, whether in the ground or raised beds.
Days to Maturity
“Days to maturity” measures the length of time it takes the seedling to fully develop or produce blooms or fruits. The seed packet or varietal information lists the number of days for production. Use this length of time in coordination with the first frost date to determine when to start fall seeds.
Count the number of days out from the frost date (or ask Google to). If you live in zone 8 and your frost is in late November, selections that take 60 days to mature benefit from a late August or early September sowing. Add a week or so for variables and delays, as the days to maturity guide is based on optimal growing conditions.
Zone Tips
Here are specific highlights by growing zone on what to grow and when to start fall seeds. Don’t forget to direct sow perennials, including many North American native species, in time to benefit from cold stratification for spring germination. Fall and even winter are prime for sowing cold-hardy perennials.
- Zone 1: The hardiest of the hardy should go in the ground in June for picking before August’s first frost. Fast-growing crops like kale, spinach, and winter radish bring a quick turnaround in the few weeks between summer and winter. Install plants like dwarf blueberry (Vaccinium caespitosum) and direct sow perennials for cold stratification and germination in spring. Snow arnica (Arnica frigida) and common alplily (Gagea serotina) are two to scatter in frosty conditions.
- Zone 2: Fall approaches quickly. Look to sow seeds that mature before the first frost in late August or early September. Kale, spinach, mustards, and winter cress are fine sowings for June and July. Direct sow perennials now to benefit from winter’s cold stratification, such as native species. For tasty greens year-round, grow them on the kitchen counter.
- Zone 3: With a short window to enjoy fall crops, plan to transplant seedlings in early to mid-summer to beat the frost in early September. This means starting as early as by mid-June, quickly developing Brassicas like bok choy, broccoli, cabbage, cauliflower, chard, collards, and kale should be starting. Seed lettuce and spinach up until mid-July.
- Zone 4: Sow in June to mid-July with an anticipated heavy frost between late September and the first week of October. Most cold-season crops should be sown by early July, with broccoli, cabbage, lettuce, and spinach trailing a bit by mid to late July.
- Zone 5: It’s a good idea to get a jumpstart by starting seeds indoors during the summer for transplanting as the weather cools. The first frost typically occurs in the middle of October. By mid-July, have broccoli, bok choy, cabbage, cauliflower, chard, and kale going. By mid-August, lettuce and spinach are ready to sow for a quick turnaround as baby greens or full-sized leaves.
- Zone 6: With an initial frost date in mid-to-late October, aim for a mid-fall harvest. Begin sowing seeds in early to mid-summer to transplant seedlings in time for a hearty harvest. Sow crops like beets, cabbage, cauliflower, chard, collards, fennel, radicchio, and turnips in mid-July. By early August, start bok choy, broccoli, carrots, and kale, followed by lettuce and spinach mid-month.
- Zone 7: Plan to revisit your favorite spring crops for another round of cool-season harvesting. Start seeds in the summer to have them ready to pick by the end of October, as the potential for the first frost falls between the very end of the month and November 15th. Starting in the summer gives time for transplanting later in the season and into early fall. With hot temperatures possible in late summer, offer cooling shade or indoor starts for sprouts.
- Zone 8: Because high heat can inhibit germination rates and seedling development for cool-season crops, plan for indoor or protective sowing in late summer. From early August to early September, start favorite Brassica varieties including broccoli, cabbage, cauliflower, chard, and kale. Carrots and root vegetables also suit this timing. Bok choy, lettuce, and spinach can go in by early October.
- Zones 9-10: In these mild, usually frost-free climates, grow cool-season selections over the winter. Begin sowing in late summer and into fall so they’ll experience cool conditions. Start sowing in mid-August on cooler ends of the zones and into October in the warmest areas.
Indoor Seed Starting for Fall
We talked about how starting seeds indoors gives the advantage of moderate conditions without exposure to late summer elements like high heat or pounding rainstorms, or the opposite, dry spells. Indoor sowing also means a devoted growing area, more intensive management than direct sowing, and related supplies. Seed-starting needn’t be expensive. Consider budget-friendly materials or make lasting investments in quality materials like reusable cell packs.
The best location for most cool-season seeds to germinate is a bright spot with temperatures between 60-70°F (16-21°C). The warmth level varies depending on the species, so it’s best to check the variety for specifics. A covered porch, cool garage, or windowsill works well. Outdoors, starting fall seeds in trays or packs under tree canopy gives them exposure to garden conditions while offering cooler temperatures for tender sprouts.
For crops with long taproots and roots sensitive to transplant disturbance, like root vegetables, opt for biodegradable pots or soil blocks. These minimize damage during transplanting.
Direct Sowing
Sowing seeds in their permanent garden location is easiest, though it may not allow enough time to reach maturity in short growing seasons. In hot climates, it may cause seedlings to sprout too quickly and wither in high heat before cool weather arrives. Use the handy days to maturity and best growing temperatures to guide direct sowing decisions.
Seeding in place helps root vegetables (like carrots and parsnips) and perennials with delicate roots, such as lupine and delphinium, avoid damage during transplanting.
Fall Vegetables and Flowers to Sow in Summer
Late summer sowings lead to a bounty of vegetables and flowers, especially those that develop in short order or last well into frosty conditions. Cold-hardy crops like Brassicas tolerate light frosts and taste better for it. Root vegetables like carrots can even be stored in the ground into winter as long as the ground doesn’t freeze for too long.
Fall vegetables to sow in summer include:
- Asian greens
- Beets
- Bush beans
- Broccoli
- Carrots
- Caulifower
- Chard
- Garlic
- Parsnips
- Peas
- Onions
- Radish
- Turnips
We know about winter sowing perennials for emergence in spring. Fast-growing annuals work with a late summer sowing, too, for a burst of color in fall. They may even reseed for another round in the spring. Cold-hardy annuals like pansies, violas, and snapdragons tolerate light frost and cold conditions. Others are frost-sensitive but bring a flurry of pollinator interest before dying back with frost.
Flowers to sow for late-season color include:
- Bachelor button
- Calendula
- Cosmos
- Marigolds
- Nasturtium
- Pansies
- Scarlet flax
- Snapdragons
- Strawflower
- Zinnia
Cover Crops
If you plan on leaving beds empty over the cool season, consider sowing a cover crop in late summer. A month or two before the fall frost, generously scatter the bare beds with a soil-improving seed selection like crimson clover, hairy vetch, or fava bean. If you have extra radish, turnip, beets, or carrot seeds, direct sow them to improve the soil before hard winter kill.
Cover crops like fall-planted grasses and legumes work with microorganisms to protect and enrich the soil between crop-growing cycles. At season’s end, turn them into organic matter by cutting them back and using them as mulch or folding them into the soil.
Cover crops also benefit pollinators in transitional seasons. Use them in raised beds, too, for soil improvement during quiet times.
