What to plant in March

March is the best month for direct-sowing cool-season vegetables outdoors in zones 6–8, for transplanting warm-season crops in zones 9–10, and for starting warm-season seedlings indoors in zones 5–7. The key mistake is rushing warm-season crops (tomatoes, peppers, squash) outdoor

March is when gardening begins in earnest for most of the country. Cool-season vegetables go directly in the ground from New England to the Pacific Northwest, warm-season transplants are moving outdoors in the South, and the indoor seed-starting calendar is at peak activity.

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What to direct sow outdoors in March

Peas — the classic March sow

Per Penn State Extension, "peas are one of the earliest vegetables that can be planted in spring." In zones 6–7, the traditional guidance is to plant peas on St. Patrick's Day (March 17) or as soon as the soil can be worked. Soil temperatures only need to reach 40°F for pea germination, though 55–65°F produces the fastest, most reliable germination.

Varieties matter for timing. Bush peas (snap and shelling types, 18–24 inches) work fine for direct sowing. Tall climbing types (up to 6 feet) need a trellis installed before planting.

In my zone 7a Long Island beds, I target the first week of March for pea sowing. Some years the soil is still frozen solid; other years it's workable. When the soil is workable but cold, a single layer of Agribon row cover row cover over the planting area warms the soil 4–6°F and improves germination timing.

Spinach, lettuce, arugula, mâche

Per Cornell Cooperative Extension, these cool-season leafy greens should be direct-sown "as soon as the soil can be worked in spring" for zones 5–7. March is the right window.

• Spinach: Germinates at 35–75°F. Direct sow 1/2 inch deep. Per Penn State Extension, "plant as early as 4–6 weeks before last frost."
• Lettuce: Germinates at 40–80°F; best at 60–65°F. Broadcast sow or drill sow 1/4 inch deep. Per NC State Extension, sow every 2 weeks for continuous harvest.
• Arugula: Germinates quickly (5–7 days) even in cold soil. Direct sow 1/4 inch deep. Very cold-hardy.
• Mâche (corn salad): Germinates at cold temperatures (40°F). Direct sow broadcast style.

Radishes

Per Penn State Extension, radishes "mature in 25–30 days" and are the fastest cool-season crop to reward March planting. Direct sow 1/2 inch deep, 1 inch apart. Thin to 2 inches when seedlings emerge.

Kale, collards, Swiss chard

These cold-hardy brassicas can be direct-sown in zones 6–8 in March. Per NC State Extension, "direct-sow kale 4–6 weeks before last frost." Swiss chard tolerates some frost and can be sown as early as mid-March in zone 6.

Beets and carrots

Beet seeds germinate at 50°F soil temperature. Per Penn State Extension, "plant beets 4–6 weeks before last frost." Sow 1/2 inch deep.

Carrots require at least 50°F for germination and benefit from more consistent warmth. In zone 6–7, late March direct sowings of carrot seed are appropriate. Carrots germinate slowly (10–21 days) — mark the row carefully and keep the soil surface moist.

Onion sets and transplants

Onion sets (small dormant bulbs) can be planted outdoors in March in zones 5–7. Per Penn State Extension, "onion sets may be planted as soon as the ground can be worked." Plant 1 inch deep, 4 inches apart.

Onion transplants grown indoors since January are ready for outdoor planting when they have pencil-thick stems. Harden off over 7–10 days before transplanting.

Potatoes

In zone 6–8, potato seed pieces can go in the ground in mid-to-late March. Per Penn State Extension, "plant when soil temperature reaches 45–50°F." Cut seed pieces to 1.5–2 ounces, with at least one eye each. Let cut surfaces cure 24–48 hours before planting. Plant 4 inches deep, 12 inches apart.