When to start melon seeds
Short answer: start melons indoors 3 to 4 weeks before planting out, and set them out about 2 weeks after your last frost once the soil is at least 65°F. Or sow directly into warm soil.
At a glance
- Start indoors
- 3–4 weeks before setting out (UNH; Iowa State)
- Set out
- About 2 weeks after last frost (UNH), when soil is at least 65°F (UMN)
- Germination temperature
- 75–80°F (Iowa State); UMN says best between 70 and 90°F
- Days to sprout
- 3–10 days (Iowa State); muskmelon 4 days at 77°F soil, watermelon 5 days (Harrington)
- Direct sow?
- Yes, once soil is at least 65°F and nights are warm (UMN)
UNH = University of New Hampshire Extension; UMN = University of Minnesota Extension; Harrington = J. F. Harrington's germination data as published by Oregon State University Extension. Full links are under Sources below.
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How many weeks before the last frost?
University of New Hampshire Extension gives melons 3 to 4 weeks from seed to transplant and says they are safe to set out 2 weeks after the last frost. With an average last frost of May 10, you would sow indoors April 26 to May 3 and set plants out May 24.
University of Minnesota Extension says transplanting can add two to four weeks to the season, which matters in the north, but warns that melons are especially sensitive to root disturbance. A plant with a broken root may never recover, or may grow slowly all season.
Starting indoors the right way
- Use peat pots or other biodegradable pots that go straight into the soil, and go larger than usual: UMN suggests pots about 4 inches across so roots have room.
- Bottom heat is essential, per UMN; use a heat mat.
- Transplant when seedlings have 2 or 3 true leaves.
- Harden off before planting out.
Germination
Harrington's data (published by Oregon State Extension) list a 60°F minimum for both muskmelon (cantaloupe) and watermelon. Muskmelon seedlings appeared in about 8 days at 68°F, 4 days at 77°F and 3 days at 86°F; watermelon in 12 days at 68°F, 5 days at 77°F and 4 days at 86°F. Iowa State Extension lists 75–80°F with emergence in 3 to 10 days. UMN says melon germination is best between 70°F and 90°F.
Soil temperature decides the planting date
UMN's rule for both direct seeding and transplanting is to wait until soil is at least 65°F in the top two inches, when nights as well as days are warm. Planting into cooler soil can lead to soil-borne root diseases that stunt or kill plants, and even healthy plants grow slowly. UMN adds that watermelon and honeydew are more cold-sensitive than cantaloupe.
To speed soil warming, UMN suggests 6 to 8 inch raised beds prepared with compost and fertilizer about two weeks before the average last frost, plus plastic mulch. Direct-sown seed goes half an inch to an inch deep, 2 or 3 seeds per group, groups 18 to 24 inches apart, rows 5 to 6 feet apart; thin to the strongest seedling. Transplants go about two feet apart in rows five feet apart.
Season length
Melons need a long, warm season. UMN notes that in northern Minnesota, melons planted in late June must be ripe before mid-September frosts. Check days to maturity and use the fall planting calculator to see whether a late planting can still ripen.
Common mistakes
- Cold soil. Wait for 65°F, not just the frost date.
- Small cells and root damage. Use 4-inch plantable pots.
- Waiting too long to transplant. Plant out at 2–3 true leaves, as UMN advises.
- Long-season varieties in short summers. Compare days to maturity with your frost-free season.
Example schedules
The same timing rules applied to three different average last frost dates. Find your own date on the frost dates page, or check your zone planting calendar for typical ranges.
| Last frost | Start indoors | Plant out | Direct sow |
|---|---|---|---|
| Mar 15 | Mar 1–Mar 8 | Mar 29 | — |
| Apr 15 | Apr 1–Apr 8 | Apr 29 | — |
| May 15 | May 1–May 8 | May 29 | — |
Supplies
Optional. You can start seeds with very little gear; these are the items that make the steps above easier. Disclosure: some links on this site may be affiliate links; if you buy through them we may earn a commission at no extra cost to you. Learn more.
- Seedling heat mat: UMN calls bottom heat essential for melons.
- 4-inch biodegradable pots: protects sensitive roots at transplant.
- Early-maturing melon seed: short seasons need fast varieties.
Frequently asked questions
When should I start cantaloupe seeds indoors?
3 to 4 weeks before planting out (UNH). Planting out is about 2 weeks after your last frost, so sow roughly 1 to 2 weeks before the last frost date.
What soil temperature do melons need?
UMN says to plant only after the top two inches of soil reach at least 65°F and nights are warm. Germination is best at 70–90°F.
Do melons transplant well?
Only with care. UMN warns melons are especially sensitive to root disturbance; use 4-inch biodegradable pots and transplant at 2–3 true leaves.
Sources
- University of New Hampshire Extension — Growing Vegetables: When to Plant Your Vegetable Garden
- Oregon State University Extension — Soil temperature conditions for vegetable seed germination (J. F. Harrington data)
- Iowa State University Extension — Germination Requirements for Annuals and Vegetables
- University of Minnesota Extension — Growing melons in the home garden
Dates in the calculator and example tables use the University of New Hampshire Extension timings. Average frost dates are not guarantees; check the forecast before setting out tender plants. Last reviewed 2026-10-23. Found an error? Tell us.