March means spring is here, and the gardening season really begins. Temperatures are rising, and while you might still have some wintery days, warm days are coming more regularly. During March, you can continue starting some of your warm-weather vegetables inside while also planting cool-season veggies directly outside. March is a great time to get ready for the big bounty in the months to come.
When starting a vegetable garden in spring, it's important to keep in mind your USDA hardiness zone and last frost date. For the warmest zones (9 and higher), it’s already safe to plant just about anything outside.
If you’re in zone 7 or 8, your average last frost date occurs in March, and you have more leeway for transplanting seedlings or to direct sow seeds outdoors. For colder climates, when to plant a vegetable garden is more impacted by your later frost-free date, which might not be until April or May. However, you can still sow seeds for several cold-weather vegetables outside in March, while starting seeds indoors is your best option for hot-weather vegetables.
Not sure what to grow? Our Ultimate Collection is your all-in-one solution with 23 vegetables, 5 herbs, and 2 flowers that span the seasons for a long harvest.
Vegetables to Plant Outside in March
Most gardeners can begin sowing seeds for cool-weather vegetables outside in March. These vegetables tolerate colder temperatures and will give you late spring or early summer harvests. Follow guidelines specific to your hardiness zone and for each vegetable.
1. Spinach
Spinach is cold-hardy, and, in fact, tastes better when grown in cool temperatures. By summer, your spinach will bolt and be unfit for eating. Sow seeds outside now, as long as the soil temperature is at least 40°F (4°C).
Spinach grows quickly, and you can harvest baby leaves or mature leaves. Sow seeds every two weeks to get a few harvests of leaves before the heat of summer arrives. Look for the hardiest varieties if you’re in a colder zone and for the first sowing and varieties that tolerate more heat for later successions.
Tundra spinach, available in the Gardening Know How Shop, is a bolt-resistant, semi-savoy variety that combines the superior taste and longer shelf life of savoy spinach with lightly crinkled, upright leaves that are a breeze to clean.
2. Lettuce
Like spinach, lettuce prefers cooler temperatures and will bolt in warmer weather. It’s safe to sow lettuce seeds outside in March in most areas, even when soil temperatures are as low as 40 degrees.
For a quick, abundant harvest, sow seeds close together and harvest baby greens. You can sow lettuce seeds in succession and get a few harvests in before the heat of summer begins. For head lettuce, sow now and expect mature plants in 40 to 50 days.
Rather than just growing one lettuce variety, opt for a seed mix. The Salad Bowl Mix Organic Greens Seeds, available in the Shop, offer a tasty combination of mild and zesty flavors, all ready to harvest around the same time. This delicious mix will take you from spring through fall.
If you're short on space, you can still enjoy the delicious taste of homegrown vegetables from your patio or balcony with this perfect collection for pots.
3. Radish
Radishes are excellent for spring growing, as they tolerate cooler weather and grow quickly. Depending on the weather and the variety you choose, they can be ready to harvest in as little as three weeks.
One of the best varieties to grow is Rivoli Hybrid Radishes, available in the Shop. They look perfect on the plate with their watermelon-red skins, while the inside is crisp, refreshing, and mildly peppery. What's more, they're resistant to disease and changeable weather.
Sow radish seeds outside in succession beginning in March to get a few spring harvests. Like other cool-weather veggies, they won’t grow well in summer. You can get several harvests in both spring and fall, though.
4. Carrots
Carrots do not transplant well, so they are best direct sown in spring for a summer crop. They may take some time to germinate in cold spring soil, but once they get going, the cooler temperatures will make them taste especially sweet. In warmer growing zones, you can direct sow carrots outside in March.
In colder zones, use soil warming techniques to raise soil temperatures enough for carrot seeds to germinate. For example, anchor a black tarp over the soil to create a greenhouse effect. This will warm the soil over the course of a week or two and allow you to plant carrots earlier.
Carrots are such staples that it pays to grow more than one variety. Try classic quick-growing Organic Nantes Carrots, available in the Shop, and add a splash of color to your garden and dinner table with Rainbow Blend Carrots.
Vegetables to Start Inside in March
Only in the warmest zones can you direct sow warm-weather vegetables outside in March. For everyone else, now is the time to get them started indoors. You can transplant them outside when temperatures are adequate for each specific type.
From delicious non-GMO vegetable seed collections to professional-quality seedling trays and kits, you'll find everything you need to start growing in the Shop.
5. Tomatoes
Tomatoes are a favorite warm-season veggie of many gardeners. They thrive in the heat of summer and produce tasty fruits in late summer and early fall. Check guidelines for the varieties you choose, but generally, it’s best to start tomato seeds five to six weeks before your last frost date.
When choosing a variety, consider your climate and what you want to use them for. For gardeners in cooler zones, Early Girl, available in the Shop, is ideal for ensuring plants produce a generous crop before summer's end. For making sauces, you'll want the perfect plum tomato, San Marzano, a staple of Italian cooking; while Supersweet 100 Hybrid Cherry is an irresistibly sweet variety for snacking that boasts a super-high vitamin C content. Alternatively, our Rainbow Blend Heirloom Tomatoes Collection offers six unique heirloom varieties for a flavorsome harvest.
Keep your germinating and sprouting tomatoes warm inside, using a heating pad if necessary. They do best in soil that is at least 70°F (21°C) but ideally even warmer.
6. Peppers
Peppers also love the heat of summer and won’t tolerate being started outdoors in early spring. Another good reason to start them indoors now is that some peppers have long maturity times. Hot peppers can take as long as 150 days to mature.
Speed things up by trying a fast-growing variety, such as Early Jalapeño Organic Pepper, available in the Shop. It matures in just 65 days from transplant and is perfect for adding that extra zing to Mexican cuisine. Or, opt for an Asian infusion with Thai Hot Peppers that pack a punch of heat ranging between 50,000 to 100,000 Scovilles.
When growing peppers, use a heating pad to keep your seed trays warm. They demand even more warmth than tomatoes. Do not transplant peppers outside until the air temperatures are consistently higher than 55°F (13°C).
7. Broccoli
Cruciferous vegetables such as broccoli are technically cool-weather veggies that will bolt in summer, but for many growing regions, they’re best started indoors in March. The soil will be a little too cold in most areas for the seeds to germinate outside.
Start broccoli indoors five to eight weeks before the last frost date. The exact timing will depend on the variety, so check the seed packet for details. Harden off seedlings before fully transplanting them in the garden. Introduce them gradually to direct sunlight and provide some wind protection for the first couple weeks they spend outdoors.
In terms of variety, Castle Dome Hybrid Broccoli, available in the Shop, has a classic look and flavor but is fast-growing and heat-tolerant, making it a versatile option for a long growing season.
8. Cauliflower
Cauliflower is also a cruciferous vegetable, and its growing requirements are much the same as broccoli, with a few key differences. While broccoli produces multiple side shoots, cauliflower produces a single head, so all the work goes towards tending to this. The plants are more sensitive to temperature, and will quickly bolt when the weather heats up. This makes it vital to plant cauliflower earlier in the season.
Cauliflower Amazing, part of our Ultimate Garden Seed Collection, produces great yields with stunning large heads, making it an ideal choice for most growers.
While the heads of colored varieties need the sun to develop, white cauliflower should be blanched to protect it from turning yellow and scalding, which changes the flavor. Once the heads are large enough, the outer leaves are loosely tied over the developing head with a soft cloth.
While cauliflower may seem like a bit more effort than some other vegetables, it's worth it as homegrown plants have such a wonderful flavor, and it's so versatile in cooking.
Use these general guidelines to start your veggie garden in March. Refer to your hardiness zone, last frost date, and seed packet instructions for specific details of when and how to plant.
More Vegetable Growing Inspiration
- Browse the best varieties of non-GMO vegetable, herb, and flower seeds in the Gardening Know How Shop. Every option has been hand-picked by experts for flavor, performance, and beauty.
- As well as these vegetables, you can also start our 7 best vegetables to plant in February this month.
- Learn how to increase tomato yields with these 7 expert tricks for a bumper harvest.
- Discover how to grow a windowsill full of veggies from a top gardening expert – perfect for the cooler spring months.
This article features products available from third party vendors on the Gardening Know How Shop.
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