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ZIP 43215 planting calendar

When to plant watermelon in Columbus, OH - Zone 6b

In ZIP 43215, plant watermelon around May 14; this uses the Columbus frost station, USDA zone 6b, and watermelon timing rules.

Your Columbus calendar has a 168-day estimated frost-free season. This estimate uses the representative Columbus frost station, USDA zone 6b, and watermelon timing rules.

Source: columbus-port-columbus frost station, USDA zone 6b, last updated 2026-06-28. Verify locally before planting high-value crops because microclimates, current weather, and yard exposure can move the safe date.

Reviewed by GrowZone Editorial. Calculated from the columbus-port-columbus frost station and USDA zone 6b, last updated 2026-06-28.

In the Columbus area, watermelon timing follows the Columbus frost window, so the local ZIP date can differ from a broad zone-only calendar.

USDA zone 6b Columbus frost station Ohio State University Extension Updated 2026-06-28
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Answer first

When to start watermelon seeds indoors in Columbus

In ZIP 43215, start watermelon seeds indoors around Apr 9, about 21 days before the Apr 30 last-frost estimate.

Start watermelon seeds indoors in Columbus around Apr 9, about 21 days before the Apr 30 last-frost estimate.

Seed starting schedule

Watermelon dates for Columbus, OH

StepDateHow to use it
Start IndoorsApril 9, 2026Start seeds under lights or in a bright indoor seed-starting space.
Transplant OutdoorsMay 14, 2026Move hardened-off seedlings outside after the frost-risk window.
Direct SowMay 14, 2026Sow seed outside when the crop and soil can handle the window.

Last frost

When is the last frost in Columbus?

Columbus (ZIP 43215) has an average last spring frost around Apr 30.

First frost

When is the first frost in Columbus?

The average first fall frost is around Oct 15, giving about 168 frost-free days.

Season map

Watermelon windows by month

JanFebMarAprMayJunJulAugSepOctNovDec
Start indoors
Apr 9
Direct sow
May 14
Transplant
May 14
Harvest
Aug 12
Frost watch
Jul 17

Reminder workflow

Every date has a next action

Start watermelon indoorsApr 9
Last frost windowApr 30
Direct sow watermelonMay 14
Transplant watermelonMay 14
Last watermelon sowing targetJul 17
First watermelon harvest windowAug 12
SignalValueWhy it matters
Last frost estimateApril 30, 2026Warm-season transplant risk starts falling after this window.
First frost estimateOctober 15, 2026Fall planting counts backward from this date.
Season length168 daysLonger seasons can support succession crops.
Spacing36-60 inAirflow and root space affect yield.
Soil temperature70 F+Seeds and transplants stall in cold soil.

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Local data

Why this date changes by ZIP

Columbus frost history and USDA zone 6b shift the safe planting window. GrowZone uses a local representative station instead of one national rule.

Ohio State University Extension is the kind of local source to verify against when a crop is expensive, weather is unusual, or your yard has a cold pocket.

Crop note

Watermelon timing notes

Wait for warm soil; watermelon stalls when nights stay cool. Watermelon prefers full sun, 36-60 in spacing, and soil near 70 F+.

For fall, count backward from Oct 15. A conservative last sowing target is around Jul 17.