7 Vegetables To Plant In September: Prolong The Growing Season With Cool-Weather Crops

As summer draws to a close, many gardeners might think it's time to pack away their tools, but September offers a unique opportunity to extend your growing season and continue enjoying the rewards of your vegetable garden. The crisp, cooler days of early fall are perfect for planting a variety of vegetables that thrive in these conditions.

Whether you're eager to extend the summer harvest or excited to grow cool-weather crops, there are plenty of vegetables to plant in September that can keep your garden productive for many months to come.

Most of our recommended vegetables to plant in August can also be started in September, so this article delves into some further staple and less obvious crops to plant this month.

In milder USDA growing zones, the possibilities are particularly abundant. These regions allow gardeners to experiment with a range of vegetables, from fast-maturing greens to heartier root crops, ensuring that the vegetable patch remains lush and productive. Spinach, kale, and radishes, for example, can quickly fill the gap left by summer’s fading bounty.

Meanwhile, those in colder zones may face more challenges, but with a bit of creativity, such as using a greenhouse or cold frames, it is possible to extend the gardening season. Overwintering crops like garlic or planting hardy varieties of carrots and beets can also help gardeners make the most of their growing space.

Whether you’re an experienced gardener or just starting a vegetable garden, September is an ideal time to start a new wave of vegetables, ensuring a bountiful harvest that can last well into the cooler months.

1. Peas

You may know that sweet peas are often sown in the fall, but did you know that garden peas can also be planted at this time?

Some smooth pea varieties, such as Meteor or Douce Provence, are surprisingly cold-hardy and can be successfully grown outdoors over winter to yield an early spring crop. Avoid wrinkled peas, as these hold moisture in the crevices, causing damage in the frosts.

Sow seed into well-draining but moist soil, enriched with organic matter, and water consistently in dry spells. As climbing plants, peas will need support – there are numerous vegetable trellis ideas that can be added at the time of planting.

The plants may be targets for rodents and other pests, but netting crops will provide protection.

Harvest peas once the pods are plump and full, and check over plants daily.

2. Fava beans

Fava beans are a staple crop in many countries and can be cooked in countless ways, as well as dried for storage. Plant a fast-cropping variety of these cool-season beans in early September for a late-fall harvest, or plant hardy long-pod varieties later in the fall for a spring harvest.

Fava beans are considered the hardiest bean, and the only type that is frost-tolerant – able to endure cold snaps as low as -10°C (14°F). Aquadulce Claudia is a popular fall-sowing variety.

Sow fava beans in fertile, well-draining soil, and keep it consistently moist but not waterlogged. Keep the site weed-free and fertilize with a phosphorus-rich formula – they do not need additional nitrogen.

If temperatures get really low or snow is forecast, protect crops with horticultural fleece.

3. Brussels Sprouts

Brussels sprouts are hardy, miniature cabbages packed with flavor and nutritional value. They are delicious in side dishes sauteed or roasted, and can also be enjoyed in stir-fries.

Though traditionally planted in the spring or summer for a fall harvest, gardeners in milder climates – zone 8 or warmer – can plant Brussels sprouts in the fall for a late winter or spring harvest. In cooler zones, they can be grown in a greenhouse. Choose late-maturing varieties such as Fortress, Stablolite, Widgeon, and Red Rubine.

Brussels sprouts require well-draining, fertile soil, rich in calcium with a pH around 5.5 to 6.8. They require staking, which is best added at the planting stage.

Fertilize with a high-phosphorus food when planting and again with a high-nitrogen feed a few weeks later.

4. Cauliflower

One of the most versatile vegetables used in cooking, cauliflower has a reputation for being difficult to grow, due to its temperature sensitivity. As a cool-weather crop, it is quick to bolt when temperatures exceed 75°F (24°C). However, it also will not tolerate frosts.

The good news is that cauliflower can be successfully started between September and November for a spring harvest, taking 5-6 months to reach maturity. However, it needs to be protected from frosts by growing it in a greenhouse or cold frame. Only plant it out in the garden after the risk of frost has passed.

Cauliflower thrives in well-draining soil rich in organic matter, with a pH between 6.0 and 7.0. Keep the soil consistently moist and fertilize with a high-nitrogen formula.

White cauliflower benefits from blanching to improve the flavor and appearance. This blocks out sunlight, preventing the vegetable from turning green-brown and developing a more bitter flavor. To do this, loosely tie the outer leaves up and over the curds when they reach the size of an egg.

Harvest cauliflower 1-3 weeks after blanching, once the head is full, but has not started to separate, and measures 6-12 inches (15-31cm) in diameter.

5. Onions

Onion sets – rather than seed – can be planted from September until November for harvesting in early summer. This gives you a headstart on the growing season, as spring-planted onions will not be ready until later in the summer.

Planting onions in the fall is only a good idea for milder growing zones. Most varieties are hardy to 20°F (-6°C) – any colder, and they’ll freeze and rot when they thaw. Growing them in raised beds can minimize frost, and you can further protect them by adding a thick layer of mulch when frost is expected

As they take so long to grow, it’s only worth planting onions in the fall if you plan to eat them as soon as you harvest them. If you want to store onions over a longer period, plant them in the spring.

Onions will rot in waterlogged soil, so they must be overwintered in free-draining soil, dug over, and enriched with compost prior to planting. They won’t require any maintenance apart from keeping the surrounding soil weed-free.

Harvest onions once the tops start to fall over and turn brown.

6. Collard Greens

Growing collard greens is traditional in the Southern states, where they are enjoyed in New Year’s Day meals as they are thought to be lucky, representing paper money. They are also very tasty and a rich source of vitamins and fiber.

In the South, collard greens are usually planted in September for a winter harvest. The crops are frost-hardy, so can also be planted in cooler zones at this time, with the frost actually enhancing their flavor. Collard greens can handle temperatures as low as 10°F to 15°F (-12°C to -9°C) without protection.

Sow seed in moist, fertile soil in a full sun location, and keep an eye out for aphids and cabbage loopers.

7. Asian Greens

There are a variety of tasty Asian greens that can be planted in September, including bok choy, napa cabbage, komatsuma, mibuna, and mizuna mustard greens. Consider buying a mixed seed pack to try a wide variety.

The leaves can be harvested as cut-and-come-again crops with baby leaves ideal for salads, and larger leaves delicious in stir-fries.

Sow seed into fertile, well-draining soil in a sunny spot, and keep the site weed-free and consistently moist. As with other greens, look out for pests such as aphids, cabbage loopers, and slugs.

This article features products available from third-party vendors on the Gardening Know How Shop.