What Are the Best Vegetables to Plant in March? (By Climate Zone)

In March, the best vegetables to plant depend on your USDA hardiness zone. In zones 6 and warmer, you can direct sow cool-season crops — peas, spinach, lettuce, kale, and carrots — directly in the ground. In zones 5–6, March is the right time to start tomatoes and peppers indoors, 6–8 weeks before the last frost. In zones 8–10, warm-season crops like beans and squash may already be going in the ground. The zone-by-zone breakdown below tells you exactly what to plant, what to start, and what to wait on.

Why USDA Hardiness Zones Matter for March Planting

"March" as a planting window means radically different things depending on where you live. In zone 4 Minnesota, March might mean 18 inches of snow and frozen ground. In zone 9 Southern California or Texas, March means full spring with warm soil already approaching 65°F (18°C).

The USDA Plant Hardiness Zone Map divides North America into zones based on average annual minimum temperatures. For vegetable gardening, the more practically useful guide is your last expected spring frost date — the average last date in spring when temperatures dip to 32°F (0°C) or below.

You can find your last frost date using:

• The USDA's online resources at usda.gov
• Your state's Cooperative Extension Service website
• The Old Farmer's Almanac frost date tool (enter your zip code)

Once you know your last frost date, count backward. Most cool-season crops can go in 4–6 weeks before that date. Warm-season crops like tomatoes and peppers should be started indoors 6–8 weeks before that date.

Cool-Season Crops: The March Stars for Most Zones

Cool-season vegetables are the reason March is such an exciting gardening month. These crops actively prefer cool soil (45–65°F / 7–18°C) and will actually bolt (go to seed prematurely) and turn bitter if they experience hot summer temperatures too early.

The UC Cooperative Extension and University of Illinois Extension both identify the following as the most reliable cool-season crops for spring direct sowing:

Peas (Direct Sow Outdoors)

• Soil temperature needed: 40–70°F (4–21°C) — one of the most cold-tolerant vegetable seeds
• How far before last frost: Can go in 4–6 weeks before last frost date, or even earlier in zones 7+
• Planting depth: 1 inch deep, 2 inches apart
• Why March is perfect: Peas need a long, cool growing season. Plant them late and they'll bolt in summer heat before producing well.

Spinach (Direct Sow Outdoors)

• Soil temperature needed: 35–70°F (2–21°C) — extremely cold tolerant
• When: Can go in as soon as soil is workable; will germinate at very low temperatures
• Why March is perfect: Spinach bolts when day length exceeds 14 hours and temperatures rise. March planting gives you a full harvest before summer arrives.

Lettuce and Salad Greens (Direct Sow or Transplant)

• Soil temperature needed: 40–70°F (4–21°C)
• When: 4–6 weeks before last frost; plant in succession every 2–3 weeks for continuous harvest
• Varieties for March: Loose-leaf types germinate faster than heading types

Kale and Swiss Chard

• Soil temperature needed: 45–85°F (7–29°C); frost-tolerant, can handle brief dips to 25°F (-4°C)
• When: March direct sow in zones 5+; zones 3–4 wait until April
• Bonus: Frost-sweetened kale is arguably better than summer kale

Carrots, Beets, and Radishes

• Soil temperature needed: 45–85°F (7–29°C) for carrots; radishes germinate reliably at 40°F (4°C)
• When: Direct sow as soon as soil can be worked
• Note: Carrots need a loose, deep, rock-free soil. Amend with compost before sowing for best root development.

Onions and Leeks

• Method: Plant onion sets (small bulbs) or transplants, not seeds, in March for most home gardeners
• Soil temperature needed: 50–95°F (10–35°C) for best germination

Zone-by-Zone March Planting Guide

Note: Last frost dates are averages based on USDA historical data. Check your local Cooperative Extension Service for the most accurate local data.

Starting Tomatoes and Peppers Indoors in March

For gardeners in zones 4–7, March is the prime window for starting tomatoes and peppers indoors. These warm-season crops need a long indoor head start because they require soil temperatures of 60–65°F (15–18°C) to thrive outdoors — temperatures that don't arrive until late May or June in colder zones.

Indoor starting timeline:

• Tomatoes: Start 6–8 weeks before your last frost date. In zone 5 (last frost May 10), start indoors early-to-mid March.
• Peppers: Start 8–10 weeks before last frost. Peppers are slower to germinate (soil temperature of 80°F / 27°C is ideal for germination) — March starting is right on schedule.
• Eggplant: Same timing as peppers.

What you need for indoor starts:

• Seed-starting trays or small pots (cell size 1.5–2 inches for initial sowing)
• Seed-starting mix (not regular potting soil — it's too heavy for tiny roots)
• Grow lights (LED full-spectrum, 16 hours/day) or a very sunny south-facing windowsill
• A heat mat to maintain 75–85°F (24–29°C) soil temperature for germination

According to the University of Illinois Extension, the single most common indoor seed-starting mistake is insufficient light. A south-facing window in March, even in a warm climate, typically delivers far less light than growing seedlings need — resulting in spindly, weak transplants that struggle after planting out. Supplemental LED grow lights make a significant difference.

How to Find Your Last Frost Date

Your last frost date is the most important number in your spring gardening calendar. Here's how to find it:

1. USDA Plant Hardiness Zone Map: planthardiness.ars.usda.gov — enter your zip code for your zone
2. Your state's Cooperative Extension Service: Search "[your state] Cooperative Extension last frost date" for highly localized data
3. Weather services: Many local weather services maintain historical frost date records

Once you have your last frost date, the planting calendar becomes simple: count backward for when to start seeds indoors, count forward for when warm-season crops are safe to go outside.

Soil Prep Before Sowing: The March Foundation

Before any seed or transplant goes in the ground, confirm your soil is ready:

1. Check soil temperature — minimum 40°F (4°C) for cold-tolerant crops; 50°F (10°C) for most others
2. Work in 2–3 inches of finished compost — improves drainage, nutrient availability, and soil structure
3. Rake to a fine tilth — small seeds like carrots and lettuce need firm, fine-textured soil for good seed-to-soil contact
4. Avoid working wet soil — if soil holds its shape and won't crumble, wait for it to dry slightly

See our complete guide to spring vegetable garden preparation for a detailed step-by-step walkthrough of bed preparation.

Quick Reference Summary Table

March Planting at a Glance:

Frequently Asked Questions

Q: Can I plant tomatoes outside in March? A: In most of the US, no. Tomatoes are killed by frost and struggle below 50°F (10°C) soil temperature. Zone 9–10 gardeners may be able to transplant out in late March, but everywhere else, March is for starting tomatoes indoors. Transplant outdoors after your last frost date has passed.

Q: What cool-season vegetables can handle frost? A: Peas, spinach, kale, Swiss chard, lettuce (light frost only), carrots, beets, and radishes all tolerate light frost (28–32°F / -2 to 0°C). Kale is exceptionally cold-hardy — established kale plants can survive temperatures down to 10–15°F (-9 to -12°C). Frost actually sweetens kale and some root vegetables by triggering the conversion of starches to sugars.

Q: What if I plant too early and a late frost is forecast? A: Protect young plants with a row cover, cloche, or even an old bed sheet. These floating row covers can add 4–8°F (2–4°C) of frost protection and are inexpensive. Keep them on hand through late May in zones 5–6.

Q: I live in zone 5. Can I plant anything outside in March? A: Yes, with care. Check your soil temperature — if it's above 40°F (4°C) and the ground isn't frozen, you can direct sow peas, spinach, and kale. These are the most cold-tolerant crops for direct sowing and can handle frost after germination. Everything else is an indoor start in March for zone 5.