What to plant in March in USDA zone 3

Sow indoors in March — zone 3

Start these seeds under lights or in a heated propagator so transplants are ready when the outdoor planting window opens.

• Tomatoes, peppers, eggplant, basil
• Brassicas (broccoli, cabbage, cauliflower, kale)
• Lettuce and other cool-season transplants (late March)

Prep and planning — zone 3

• Garden beds — Snow may still cover the ground; start indoor work in earnest.

Universal March tasks

These apply across most US and UK gardens in March, regardless of zone.

• Start tomato, pepper, and eggplant seeds indoors (if not already).
• Direct-sow peas, spinach, lettuce, radishes once soil is workable.
• Transplant onions and leeks outdoors in zones 5-9.
• Plant bare-root fruit trees, berries, and asparagus crowns.
• Prune roses just before they break dormancy.
• Top-dress beds with compost and start hardening off transplants.

Why this works for zone 3

Zone 3 has average annual minimum temperatures of -40 to -30°F (-40 to -34°C) and a frost-free window from late May to early September — about 110 growing days. Frost-tender vegetables need row covers and short-season varieties. Heat-loving crops (peppers, eggplant) require greenhouses or season extension.

Dates are zone-wide averages. Local microclimates (south-facing slopes, urban heat, lakeside warmth, elevation) can shift the window by 1-2 weeks within the same zone.

UK gardeners — March

March opens outdoor sowing for most of the UK. Direct-sow peas, broad beans, spinach, radishes, and early carrots under cloches. Indoor: tomatoes, peppers, aubergines, cucumbers. Plant first early potatoes mid-month.

Source and methodology

Frost-date averages from NOAA Climate Data Online within USDA zone 3. Hardiness boundaries from the USDA Plant Hardiness Zone Map (2023). Crop timing curated against US Cooperative Extension Service publications (UNL, UMN, NC State, Texas A&M, UF/IFAS, Oregon State) and cross-referenced against the RHS sowing calendar. Curated by the Growli editorial team.

Keep going

• ← February in zone 3
• April in zone 3 →
• All zones — what to plant in March
• USDA Zone 3 — frost dates and crop list
• Full 12-month planting calendar

Other zones — March

• What to plant in March in zone 4
• What to plant in March in zone 5
• What to plant in March in zone 6
• What to plant in March in zone 7
• What to plant in March in zone 8
• What to plant in March in zone 9
• What to plant in March in zone 10