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When to Plant Watermelon

Plant watermelon after your last spring frost, once the soil is at least 60-65°F at a 4-inch depth, which is usually 1 to 3 weeks after the average last frost date. Start transplants indoors 3 to 4 weeks before that date. In warm-winter areas such as South Florida, plant from December through March instead.

Your dates for watermelons

Set your ZIP code at the top of the page and we will work out when to plant watermelons where you live, from the frost records of the nearest NOAA weather station. Your ZIP code is remembered on this device only.

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Watermelons planting dates by zone

JFMAMJJASOND Zone 4b Zone 5b Zone 6b Zone 7b Zone 8b Zone 9a
Start indoorsPlant out or sowFirst harvestDates use each zone's typical frost dates. Enter your ZIP code for your own.
Dates from each zone's typical (median) frost dates. Select a zone for the full schedule.
ZoneStart indoorsPlant outSow outdoors
Zone 2aMay 13 to 27Jun 17 to Jul 1Jun 17 to Jul 1
Zone 3aMay 7 to 21Jun 11 to 25Jun 11 to 25
Zone 3bMay 4 to 18Jun 8 to 22Jun 8 to 22
Zone 4aApr 28 to May 12Jun 2 to 16Jun 2 to 16
Zone 4bApr 23 to May 7May 28 to Jun 11May 28 to Jun 11
Zone 5aApr 18 to May 2May 23 to Jun 6May 23 to Jun 6
Zone 5bApr 18 to May 2May 23 to Jun 6May 23 to Jun 6
Zone 6aApr 14 to 28May 19 to Jun 2May 19 to Jun 2
Zone 6bApr 7 to 21May 12 to 26May 12 to 26
Zone 7aMar 31 to Apr 14May 5 to 19May 5 to 19
Zone 7bMar 22 to Apr 5Apr 26 to May 10Apr 26 to May 10
Zone 8aMar 8 to 22Apr 12 to 26Apr 12 to 26
Zone 8bFeb 24 to Mar 10Mar 31 to Apr 14Mar 31 to Apr 14
Zone 9aFeb 7 to 21Mar 14 to 28Mar 14 to 28
Zone 9bFeb 1 to 15Mar 8 to 22Mar 8 to 22

The rule: warm soil, not just a frost-free date

Watermelon is frost-tender, so nothing goes out until frost danger is over. But the frost date alone isn’t enough, because melon seed germinates poorly in cold soil. The extension standards differ slightly:

  • Clemson: 60 to 65°F at a 4-inch depth.
  • Iowa State: 60 to 70°F.
  • Utah State: 65°F.

In practice, this means planting 1 to 3 weeks after your average last frost, which is the window in the dates for your zone above. A soil thermometer pushed 4 inches deep gives you the real answer for your garden. If a cold, rainy stretch arrives at planting time, wait it out. Iowa State warns that cool, wet soil invites Pythium damping-off, and it is better to plant a little late than to lose the stand.

Air temperature matters too. Clemson notes that watermelon grows best at average air temperatures of 70 to 85°F, and cool, rainy or windy weather at bloom keeps bees from pollinating the flowers.

Timing transplants

Transplants ripen about two weeks ahead of direct-seeded melons (Clemson, Utah State), which can make the difference in a short season. Work backward from your outdoor planting date:

  • Iowa State: sow in peat pots 3 to 4 weeks ahead and transplant at 1 or 2 true leaves.
  • Utah State: allow about 6 weeks to grow plants with 2 to 3 mature leaves.

Use plantable pots, because watermelon roots don’t like being disturbed. Harden the seedlings outdoors for a few days before planting.

Planting earlier with plastic and row covers

Black plastic mulch warms the soil faster than bare ground. Utah State says that with plastic mulch and row covers together, seeds or transplants can go out 2 to 3 weeks before the last frost. Vent the covers when air temperatures reach 80°F, and take them off when plants flower or temperatures exceed 90°F. Lay organic mulch such as straw only after the soil passes 75°F, or it will keep the ground cold.

Regional windows

Upper Midwest and North. Iowa State plants in mid-May in central Iowa, about a week earlier in southern Iowa and a week later in the north. June 20 is the last practical sowing date for early-maturing varieties. In short-season areas, Utah State recommends transplants.

Southeast. Clemson’s South Carolina windows run from April 1 to 30 on the coast and from April 15 to June 15 in the Piedmont. It does not recommend fall plantings.

Florida. UF/IFAS lists late March through April for North Florida, plus a second window in July and August. Central Florida plants January through March, and South Florida December through March.

Low desert. The University of Arizona calendar for the Phoenix area schedules seeding from mid-February through March, using varieties that take 90 to 120 days, so vines fruit before the hottest months.

How late is too late

Watermelon takes a long time to mature. UF/IFAS gives 80 to 100 days from seed (60 to 90 from transplants), the Arizona calendar 90 to 120 days, and Clemson about 85 to 90 days from transplanting to the first ripe fruit. To find your last practical planting date, count back the variety’s days to maturity from your first fall frost and leave a margin. If you are planting late, choose a small, early icebox type.

For spacing, feeding, watering and harvest signs, see the watermelon growing guide.

Where frost is rare

Plant in late winter to early spring so the vines fruit before peak summer heat. North Florida gets a second, midsummer planting window.

ZonePlanting months in Extension guides
Zone 9Jan-Mar (Central FL); mid Feb-Mar (Phoenix low desert)
Zone 10Dec-Mar

Based on UF/IFAS Florida Vegetable Gardening Guide (VH021) Table 1: North FL late Mar-Apr and Jul-Aug, Central FL Jan-Mar, South FL Dec-Mar. University of Arizona AZ1005 Maricopa County calendar: seed from mid-February through March. zone_9 uses Central FL plus Phoenix and zone_10 uses South FL. No source covers zone 11 specifically, although VH021's South Florida dates likely apply to frost-free South Florida. Warm-winter areas are matched to zones approximately, so use the months for your region.

How to grow watermelonsYour full planting calendar

Questions

What soil temperature do watermelon seeds need?

Clemson wants 60 to 65°F at a 4-inch depth, Iowa State 60 to 70°F, and Utah State 65°F. Seed planted into colder soil comes up slowly and unevenly and is prone to damping-off.

When should I start watermelon seeds indoors?

Iowa State starts them in peat pots 3 to 4 weeks before the outdoor planting date. Utah State allows about 6 weeks to grow transplants with 2 to 3 mature leaves.

What is the latest you can plant watermelon?

It depends on your frost date and the variety's days to maturity. In Iowa, the last practical date for early-maturing varieties is June 20. Count back the full days to maturity, plus a margin, from your first fall frost.

Can you plant watermelon for a fall crop?

Clemson does not recommend fall plantings in South Carolina. Among the sources here, only UF/IFAS lists a midsummer planting, for North Florida in July and August.

Sources