What to Plant in September in the US: by USDA Zone

In the United States, knowing what to plant in September depends entirely on your local USDA hardiness zone and the countdown to your first autumn frost. For northern growers, September is a race to sow quick-maturing greens before the ground freezes, while southern gardeners are initiating a complete second growing season. By aligning your planting schedule with your specific zone band, you can maximize late-season yields and establish crops for spring overwintering.

Zones 3 and 4: Northern tier and mountain regions

First frost often arrives in mid-to-late September or early October in these cold climates. The planting window is rapidly closing, and activities focus on fast-growing crops or those meant to overwinter.

1. Direct-sowing fast-maturing greens

Focus on crops that mature in 30 days or less. Sow spinach, leaf lettuce, and radishes directly into beds. These crops can survive light frosts and will continue growing under protective covers. Radishes are particularly reliable, often reaching harvestable size in less than four weeks when sown in early September. Ensure the soil remains moist during the initial germination phase, as early autumn winds can dry out the top inch of soil quickly.

2. Establishing overwintering spinach

Plant spinach seeds in mid-September to let them germinate and reach the seedling stage before entering winter dormancy. These young plants will stop growing once freezing temperatures arrive, but they will resume growth early next spring, providing an exceptionally early harvest. Avoid fertilizing these plants in late September, as tender new growth is highly susceptible to freeze damage.

3. Utilizing cold frames and row covers

Sow arugula and mustard greens inside cold frames or under heavy row covers. The added protection keeps soil temperatures high enough to support germination and steady growth even as night temperatures drop toward freezing. Keep the covers closed on cold nights, but vent them during sunny days to prevent heat buildup, which can cause young greens to bolt or wither.

Zones 5 and 6: Midwest, Northeast, and Mid-Atlantic

The first autumn frost in these zones typically occurs in mid-to-late October. September is a highly active month for establishing cold-hardy fall and winter vegetables that will mature during the cool, bright days of autumn.

1. Direct-sowing cool-season root crops

Direct-sow radishes, turnips, and spinach. Turnips sown now will produce sweet roots after the first light frosts of October, as cold temperatures trigger the conversion of starches into sugars. Sow seeds at a depth of half an inch, and thin seedlings to three inches apart once they emerge. Keep the soil evenly damp to prevent the roots from becoming woody or bitter.

2. Transplanting brassicas and leafy greens

Set out transplants of kale, collards, Swiss chard, and cabbage. These transplants should have been started in July or August. Planting them now ensures they establish strong root systems before the day length drops below 10 hours in November, which naturally halts plant growth. Apply a thick layer of organic mulch around the base of each transplant to preserve soil moisture and buffer root temperatures.

3. Sowing overwintering crops

Sow hardy varieties of spinach and corn salad (mache). To understand how to manage these crops through the coldest months, consult our guide to overwinter garlic, spinach, and kale for an early spring harvest. These plants require minimal maintenance once established, needing only occasional watering during dry, ice-free winter spells.

Zones 7 and 8: Upper South and Pacific Northwest

With first frosts usually held off until November, September is the premier month for fall planting in these regions. The soil is warm, which accelerates germination, while the cooling air temperatures reduce pest pressure.

1. Direct-sowing autumn root crops

Sow carrots, beets, and turnips directly into prepared garden beds. Keep the seedbeds consistently moist, as early September can still experience warm, dry spells that dry out shallow seeds. Covering the newly sown rows with a light layer of straw or burlap can help retain moisture until the seeds germinate, after which the cover must be removed immediately.

2. Transplanting fall brassicas

Plant out sturdy starts of broccoli, cauliflower, Brussels sprouts, and kale. These crops thrive in the mild autumn temperatures of the Upper South and Pacific Northwest, developing superior flavor after exposure to light autumn frosts. Space the transplants 18 inches apart to allow adequate airflow, which reduces the risk of fungal diseases during damp autumn days.

3. Sowing leafy greens for winter harvest

Sow mustard greens, arugula, leaf lettuce, and Swiss chard. In the milder parts of Zone 8, these leafy crops will provide continuous harvests throughout the winter with minimal protection. Sowing in successive intervals of two weeks throughout September ensures a continuous supply of young, tender leaves rather than a single large harvest.

Zones 9 and 10: Gulf Coast, Southwest, Florida, and California

In these hot climates, September represents the beginning of the primary growing season. As summer heat begins to break, gardeners can initiate fall gardening in the Deep South and Gulf Coast with both warm-season and cool-season crops.

1. Starting warm-season transplants

In frost-free areas, sow seeds of tomatoes, peppers, and eggplants indoors or in shaded areas for transplanting out in late September or October. These will produce a late autumn or winter harvest. Because the early September sun remains intense, providing partial shade for young seedlings is necessary to prevent sunscald and heat stress.

2. Direct-sowing root crops and legumes

Direct-sow bush beans, pole beans, carrots, beets, and radishes. The soil is warm enough to ensure rapid germination, but regular irrigation is necessary to prevent the topsoil from baking. Mulching the rows lightly with clean straw can help keep the soil surface cool and moist during hot afternoon hours.

3. Establishing cool-season brassicas

Start seeds of broccoli, cabbage, kale, and cauliflower in starter trays. Keep them in a shaded location to protect young seedlings from intense September afternoon sun before transplanting them into the garden in October. This temporary shade setup prevents the young plants from bolting prematurely due to high temperatures.

Essential September gardening jobs across the zones

Beyond planting, completing fundamental maintenance tasks in September prepares the garden for the winter months and ensures a successful spring start.

1. Calculating frost dates and planning protection

Use the agripure frost dates tool to determine the average date of the first freeze in your specific ZIP code. Count backward from this date to schedule any late-season sowings, ensuring your crops have enough time to mature. Keep frost blankets or old bedsheets on hand to cover tender crops when the first sudden frost warning is issued.

2. Prepping garlic and bulb beds

Clear spent summer crops and amend the soil with aged compost in preparation for planting garlic, shallots, and spring-flowering bulbs next month. Garlic requires well-drained soil rich in organic matter to develop large bulbs, so working compost into the top six inches of soil now allows it to settle before planting begins.

3. Managing irrigation transitions

As day lengths shorten and temperatures cool, plants transpire less water. Adjust your irrigation schedules to prevent overwatering, which can lead to root rot and fungal issues in the cooling soil. Monitor soil moisture manually by inserting a finger into the top two inches of soil before running irrigation systems.