September is the most underused month in gardening. Most gardeners treat it as the end — pull the last tomatoes, yank the spent beans, dump everything in the compost, and call it a season. But September is not the end. It is a second beginning. The soil is warm, the days are still long enough for photosynthesis, and the cool-season crops that struggled in July heat now have ideal conditions to thrive. Fall gardening is not a consolation prize for people who miss summer. It is some of the best gardening of the year.
The crops you plant in September — kale, spinach, radishes, turnips, lettuce — actually taste better when grown in fall than in spring. Cold temperatures convert starches to sugars in many vegetables, producing sweeter, more intense flavors. Fall kale that has been touched by a few light frosts is a completely different vegetable from the bitter, tough kale you harvested in June. Fall spinach is so sweet it barely needs dressing. This is not opinion — it is plant physiology. Cold stress triggers sugar production as a natural antifreeze, and you get to eat the result.
This guide covers everything you should be doing in September to extend your harvest through November and beyond, prepare your soil for next spring, and close out the summer garden without wasting what it produced. Our fall planting guide for raised beds covers crop selection in more detail, while this article focuses on the full September task list.
Fall Crop Planting: What Goes In Now
The window for fall planting is shorter than you think. Count backward from your first expected frost date. Most fall crops need 6 to 8 weeks of growing time before hard frost shuts them down. If your first frost date is October 15, your last planting date for most fall crops is around August 15 to September 1. If your first frost is November 15, you have until early to mid-October. But here is the crucial detail — even if you are planting on the edge of your window, plants that are established before frost can continue growing and producing under protection well past the frost date.
Kale: The king of fall gardening. Direct-sow seeds or transplant seedlings in early September. Kale tolerates frost down to about 10 degrees Fahrenheit and actually improves in flavor after cold exposure. Lacinato (dinosaur kale), Red Russian, and Winterbor are excellent fall varieties. Plant 18 inches apart in full sun. Kale planted in September will produce harvestable leaves in October and continue through December or even January in zones 6 and warmer. In colder zones, row cover extends the harvest by several weeks.
Spinach: Direct-sow in early to mid-September. Spinach germinates in soil temperatures from 40 to 75 degrees, but established plants tolerate temperatures as low as 20 degrees. Bloomsdale Long Standing is a classic fall variety with thick, savoy leaves. Space, Tyee, and Regiment are smooth-leaf types that are easier to clean. Sow seeds 1/2 inch deep and 2 inches apart, thinning to 4 to 6 inches. September-sown spinach reaches harvestable size in 6 to 8 weeks and holds well into winter under light protection.
Radishes: The fastest fall crop. Direct-sow in September for harvest in October — most varieties mature in 25 to 30 days. Cherry Belle, French Breakfast, and Easter Egg are quick-maturing standards. For something different, try daikon radishes, which take 60 to 70 days but produce enormous roots and double as a tillage radish that breaks up compacted soil. Sow daikon in early September for a November harvest.
Turnips: Direct-sow in September. Hakurei (Japanese salad turnip) matures in 38 days and is sweet enough to eat raw. Purple Top White Globe takes 55 days and stores well. Both the roots and the greens are edible. Sow seeds 1/2 inch deep and thin to 4 to 6 inches apart. Turnips tolerate light frost and improve in sweetness as temperatures cool.
Lettuce: Direct-sow or transplant in September. Fall lettuce grows in ideal conditions — cool days, shorter photoperiod, and lower pest pressure than spring. Bolt-resistant varieties are less critical in fall because cooling temperatures naturally suppress bolting. Sow every two weeks through September for staggered harvests. Protect with row cover when frost threatens — lettuce tolerates light frost (28 to 32 degrees) but is killed by hard frost below 25 degrees.
Asian greens: Tatsoi, mizuna, bok choy, and Chinese cabbage are exceptional fall crops. They mature quickly (30 to 50 days), tolerate frost, and thrive in the cool, moist conditions of autumn. Direct-sow in September and thin to 6 to 8 inches apart. These greens are underused in American gardens but deliver outstanding flavor and nutrition from September through November.
Garlic Planting: The Most Important September Task in Many Zones
September through October is garlic planting season in most of the country. Garlic is planted in fall, overwinters in the ground, and is harvested the following June or July. It is one of the longest-season crops a gardener can grow, and getting it in the ground at the right time is essential for proper root establishment before winter.
The ideal planting window is 4 to 6 weeks before the ground freezes. In zones 3-4, that means mid-September to early October. In zones 5-6, late September to mid-October. In zones 7-8, October to early November. The goal is for each clove to develop a strong root system (6 to 8 inches of roots) without sending up significant top growth before winter. Some green shoots above the surface are normal and not harmful — they will die back in hard frost and regrow in spring.
Choose between hardneck and softneck varieties. Hardneck garlic produces a flower stalk (scape) in spring, has larger but fewer cloves per head, and stores for 4 to 6 months. It is the better choice for zones 3 through 7 because it requires a cold vernalization period to form bulbs. Softneck garlic does not produce a scape, has more but smaller cloves per head, and stores for 8 to 12 months. It is adapted to milder climates (zones 7 through 10) and is the type sold in grocery stores.
Plant individual cloves (separated from the head just before planting) pointed end up, 2 to 3 inches deep, and 6 inches apart. Mulch with 4 to 6 inches of straw after planting — this insulates the soil through winter, suppresses weeds in early spring, and retains moisture. Do not water heavily after planting unless conditions are very dry — garlic cloves can rot in soggy soil before roots develop.
Buy seed garlic from a reputable supplier rather than planting grocery store garlic. Grocery store garlic is often treated with sprout inhibitors and may carry diseases. Seed garlic is certified disease-free and comes in named varieties so you know what you are growing. Order by August for September planting — good seed garlic sells out early.
Cover Crop Seeding: Investing in Next Year's Soil
As you clear spent summer crops, do not leave beds bare. Empty beds over winter erode, lose nutrients to leaching, and develop compaction and crust from rain impact. Cover crops solve all of these problems while actively building soil fertility and structure. Our guide on cover crops for raised beds covers this topic in depth, but here is the September-specific guidance.
The best September cover crops for home gardeners are winter rye, crimson clover, hairy vetch, and field peas. Your choice depends on your goals.
Winter rye (cereal rye): The most reliable fall cover crop. Germinates quickly, grows in cool temperatures, survives winter in all zones down to zone 3, and produces massive amounts of biomass that adds organic matter to the soil. Sow at 2 to 3 pounds per 1,000 square feet. Winter rye is a grass, so it does not fix nitrogen, but it scavenges existing soil nitrogen and prevents it from leaching away over winter. Terminate in spring by cutting at ground level 2 to 3 weeks before planting.
Crimson clover: A nitrogen-fixing legume that adds 70 to 150 pounds of nitrogen per acre through its symbiotic relationship with Rhizobium bacteria. Sow in September at 1/2 pound per 1,000 square feet. Crimson clover overwinters in zones 6 and warmer — in colder zones, it winterkills and becomes a natural mulch that decomposes in place. The spring flowers are beautiful and attract pollinators.
Hairy vetch: Another nitrogen-fixing legume, more cold-hardy than crimson clover (survives to zone 4). Sow in September at 1 to 2 pounds per 1,000 square feet. Hairy vetch is a vigorous grower that fixes significant nitrogen and produces dense ground cover that suppresses weeds. It can be aggressive — terminate it thoroughly in spring before it goes to seed.
Field peas (Austrian winter peas): A short-season nitrogen-fixer that works well in zones 6 through 9. Sow in September at 2 to 4 pounds per 1,000 square feet. Field peas winterkill in zones 5 and colder, which makes spring termination effortless — the dead vines decompose in place as a mulch. In milder zones, they overwinter and need to be cut in spring.
Mix cover crop species for maximum benefit. A classic combination is winter rye and crimson clover (or hairy vetch) — the grass provides carbon and structure while the legume fixes nitrogen. This mix covers the soil densely, adds both carbon and nitrogen, and supports a diverse soil microbial community.
Preserving Summer Surplus
September is harvest peak for tomatoes, peppers, squash, and herbs. If you have more than you can eat fresh — and most productive gardens do — now is the time to preserve the surplus so nothing goes to waste.
Tomatoes: Roast halved tomatoes at 400 degrees with olive oil, salt, and garlic until concentrated and caramelized (about 45 to 60 minutes). Freeze in quart bags laid flat for easy stacking. Alternatively, make a big batch of plain crushed tomato sauce — core and quarter tomatoes, simmer for 30 minutes, run through a food mill to remove skins and seeds, and freeze. One productive tomato plant produces 10 to 15 pounds of fruit over a season — that is a winter's worth of pasta sauce from a single plant.
Peppers: Roast, peel, and freeze. Or dice fresh peppers and freeze in a single layer on a sheet pan, then transfer to bags — individually frozen pieces are easy to grab in the quantity you need. Hot peppers can be dried whole by stringing them and hanging in a dry, ventilated space, or dehydrated in a food dehydrator and ground into powder.
Herbs: Harvest herbs before the first frost kills tender types (basil, cilantro). Freeze basil in ice cube trays with olive oil for instant pesto starters. Dry oregano, thyme, rosemary, and sage by hanging bundles upside down in a dry, ventilated room for 1 to 2 weeks. Strip dried leaves from stems and store in airtight jars. Home-dried herbs are dramatically more flavorful than commercial dried herbs because they are fresher and have not been sitting in a warehouse for a year.
Winter squash: Cure butternut, acorn, delicata, and other winter squash in a warm (80 to 85 degrees), dry, well-ventilated space for 10 to 14 days. Curing hardens the skin and converts starches to sugars, improving both storage life and flavor. After curing, store in a cool (50 to 55 degrees), dry space. Properly cured butternut squash stores for 3 to 6 months. Delicata stores for 2 to 3 months. Acorn stores for 1 to 2 months.
Cleaning Spent Beds
As summer crops finish producing, clear them promptly. Spent plants left in the garden become disease reservoirs and pest habitat. A tomato plant with late blight that sits in the bed through October is broadcasting fungal spores across your garden. A squash vine killed by vine borers is an overwintering site for next year's borers. Clean removal breaks these cycles.
Pull entire plants, roots and all. Shake excess soil from roots back into the bed. If plants were healthy all season, compost them. If plants showed signs of disease (blight, powdery mildew, wilts, viral symptoms), discard them in the trash rather than composting — home compost piles rarely reach temperatures high enough to kill all pathogens.
After removing spent plants, top-dress the bed with 1 to 2 inches of finished compost. This replenishes organic matter and feeds soil biology through the fall and winter. If you are not planting a fall crop or cover crop in the bed, cover it with a 3 to 4 inch layer of mulch (straw, shredded leaves, or wood chips) or a tarp to prevent erosion and weed growth. Bare soil over winter loses topsoil to rain, develops surface crust from impact compaction, and grows weeds that get a head start before you return in spring.
Extending the Season With Row Covers and Low Tunnels
Row covers transform September plantings from short-season crops into long-season producers. A lightweight row cover (0.5 to 0.9 ounce per square yard) provides 2 to 4 degrees Fahrenheit of frost protection. A medium-weight cover (1.25 ounces per square yard) provides 4 to 8 degrees of protection. Heavy row covers and low tunnels with clear plastic can keep crops productive well past the first hard frost.
A low tunnel is a row of wire or PVC hoops covered with row cover fabric or clear greenhouse plastic. It creates a miniature greenhouse over your bed, trapping solar heat during the day and releasing it slowly at night. A simple low tunnel over a bed of kale, spinach, and lettuce can extend your harvest by 4 to 8 weeks past the unprotected frost date. In zones 6 and 7, this means harvesting fresh greens through December. In zones 4 and 5, it means harvesting into November.
Install hoops and have row cover ready before your first frost date arrives. Do not wait until frost is forecast tonight and then try to set up infrastructure in the dark. September is the month to install hoops — even if you do not deploy the cover until October. Hoops set 3 to 4 feet apart along the bed, 18 to 24 inches tall for low tunnels, with fabric or plastic draped over and secured at the edges with clips, sandbags, or buried edges.
Ventilate covered beds on sunny days. Even in October, a sealed low tunnel can overheat in direct sun, cooking the crops you are trying to protect. Lift the ends or sides of the covering when daytime temperatures exceed 50 degrees and close them in late afternoon to trap heat for the night. Automatic vent openers designed for cold frames can be adapted to low tunnels if you want hands-free ventilation.
Frequently Asked Questions
Is September too late to plant a fall garden?
It depends on your zone and your first frost date. In zones 7 through 10, September is prime fall planting time with weeks of growing weather ahead. In zones 5 and 6, early September plantings of fast-maturing crops (radishes, lettuce, spinach) will produce before hard frost, especially under row cover. In zones 3 and 4, September is borderline — focus on very fast crops like radishes and salad greens, and plan to use frost protection. The key is counting backward from your first expected frost date and choosing crops that mature within that window.
Can I plant garlic in September or should I wait until October?
The ideal window is 4 to 6 weeks before your ground freezes. In zones 3 through 5, late September to early October is ideal. In zones 6 and 7, mid-October is often better. In zones 8 through 10, November planting works. If you plant too early, garlic sends up excessive top growth that can be damaged by severe cold. If you plant too late, roots do not establish before freeze-up. Check your average ground freeze date and count backward 4 to 6 weeks for your target planting date.
What cover crop should I plant if I have never planted one before?
Winter rye (cereal rye) is the easiest starting point. It germinates reliably in cool soil, grows in all zones, overwinters without winterkilling, and requires no inoculant or special treatment. Broadcast seed at 2 to 3 pounds per 1,000 square feet over cleared beds, rake lightly to cover seeds, and water once. It will germinate in 5 to 7 days and establish a green cover before cold weather. In spring, cut it at ground level 2 to 3 weeks before planting and let the residue decompose in place.
How do I know when to pick the last tomatoes before frost?
Harvest all mature and nearly mature tomatoes before the first frost. Any tomato that has started to change color — showing the first blush of pink, orange, or red on a green background — will ripen indoors on a countertop at room temperature. Green tomatoes that show no color change will not ripen reliably. Fully green tomatoes can be used for fried green tomatoes or green tomato chutney. Do not refrigerate tomatoes that you want to ripen — cold temperatures stop the ripening process.
Should I remove all mulch from beds in September?
Only if you are planting into the bed and need the soil to warm up or be directly accessible for seeding. For beds where you are planting fall crops, pull mulch back, plant, and then replace the mulch around established seedlings. For beds you are putting to rest for winter with a cover crop or a compost top-dress, leave existing mulch in place and add more on top. Mulch protects soil through winter — removing it exposes bare soil to erosion, compaction, and nutrient leaching.