When to plant melons & cantaloupe in Portland, Maine
May 10 – May 24
Transplant outdoors · typical Portland yearClimate basis: NOAA station Portland INTL Jetport, ME (USW00014764), 2 mi (4 km) from downtown Portland (ZCTA 04101 centroid), elevation 45 ft, on the 1991–2020 climate normals. Transplant melons & cantaloupe outdoors from approximately the dates above, anchored to the median last spring 32°F freeze (April 26). One year in ten still freezes after May 7.
The Portland year
- indoors under lights
- in the garden
- frost-free season
- 1-in-10 years still freeze to May 7
Every method, with its sources
Start seeds indoors
Apr 12 – Apr 19Sow in pots 3–4 weeks before the outdoor window opens (UNH 3–4 weeks; Missouri G6570 3–5 weeks). Anchored to the median last spring freeze (Apr 26). University of New Hampshire Extension · University of Missouri Extension
Transplant outdoors
May 10 – May 24UNH: set out melons 2 weeks after the last frost; Purdue very-tender class agrees. Anchored to the median last spring freeze (Apr 26). University of New Hampshire Extension · Purdue University Extension
Direct-sow outdoors
May 10 – May 24Purdue: very tender — at least two weeks after the average last frost; Penn State earliest sowing May 15 (+14) agrees. Anchored to the median last spring freeze (Apr 26). Purdue University Extension · Penn State Extension (York County Master Gardeners)
Variety assumption: Assumes an average muskmelon variety (about 75–85 days; Penn State lists 75).
These windows describe typical years (1991–2020 climate normals), not this year's forecast. Freezes happen outside them — especially in frost pockets, valleys, and urban edges. Watch the forecast before committing tender plants.
Crop rule sources (4)
- University of New Hampshire Extension: Growing Vegetables: When to Plant Your Vegetable Garden [fact sheet] (accessed 2026-07-24)Per-crop 'time from seed to transplant' and 'safe to set out in garden' relative to last frost.
- University of Missouri Extension: Starting Plants Indoors from Seeds (G6570) (accessed 2026-07-24)Weeks needed to grow vegetable transplants indoors (Table 2).
- Purdue University Extension: Indiana Vegetable Planting Calendar (HO-186-W) (accessed 2026-07-24)Hardiness classes: hardy = plant 4-6 wk before last spring frost; semi-hardy = 2-4 wk before; tender = after average last frost; very tender = at least 2 wk after. Table 2: fall planting at least 4-8 wk before first fall frost.
- Penn State Extension (York County Master Gardeners): Vegetable Seed Planting Guide (accessed 2026-07-24)Earliest/latest sowing dates for a May 1 last-frost / Oct 1 first-frost baseline; offsets derived by date difference from May 1. Also days-to-maturity figures.