May · USDA Zone 3
springWhat to plant in May in USDA zone 3
Spring planting guide for zone 3 (Northern Minnesota, North Dakota, interior Alaska) — a 110-day growing season with last frost around late May and first frost around early September.
Sow outdoors in May — zone 3
Direct-sow these seeds into prepared garden beds or large containers. Soil temperature matters more than the calendar date — wait for a sustained warm-up before sowing tender crops.
Transplant in May — zone 3
Move hardened-off seedlings into the garden. Tender crops want soil above 16 °C and night temperatures consistently above 10 °C; cool-season transplants tolerate light frost.
- Brassicas, onions, leeks, lettuce, potatoes
- Tomatoes (very late May, after last frost in early June) — Use row cover for any cold nights.
Maintenance in May — zone 3
- Cold-frame protection on cool nights
Universal May tasks
These apply across most US and UK gardens in May, regardless of zone.
- Plant warm-season crops after last frost — tomatoes, peppers, beans, cucumbers, squash.
- Mulch beds heavily once soil has warmed to retain moisture.
- Stake or cage tomato plants before they sprawl.
- Direct-sow corn, beans, cucumbers, squash, and melons once soil hits 16 °C.
- Begin succession sowing of bush beans every 2-3 weeks.
- Pinch herbs to encourage bushy growth.
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 — May
May is the UK's tender-crop month. Plant out tomatoes, peppers, courgettes, runner beans, and sweetcorn after the last frost (typically mid- to late May). Direct-sow French beans, courgettes, sweetcorn, and squashes. Harvest asparagus, rhubarb, and first lettuce.
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
- ← April in zone 3
- June in zone 3 →
- All zones — what to plant in May
- USDA Zone 3 — frost dates and crop list
- Full 12-month planting calendar