When should I plant radishes in ZIP 96813?

In ZIP 96813, the main radishes target is around Dec 4, based on the representative Honolulu frost station and USDA zone 12b.

When should I start radishes seeds indoors in 96813?

Radishes is usually direct-sown for ZIP 96813. Use the Dec 4 planting window instead of starting it indoors.

Is this a guaranteed planting date?

No. GrowZone uses frost-date estimates, hardiness zones, and crop timing rules for planning. Local microclimates and current weather can shift the right date.

ZIP 96813 planting calendar

When to plant radishes in Honolulu, HI - Zone 12b

Q: When is the first frost in Honolulu?

Honolulu (ZIP 96813) has an average first fall frost around Dec 31, leaving about 364 frost-free days.

In ZIP 96813, plant radishes around Dec 4; this uses the Honolulu frost station, USDA zone 12b, and radishes timing rules.

Your Honolulu calendar has a 364-day estimated frost-free season. This estimate uses the representative Honolulu frost station, USDA zone 12b, and radishes timing rules.

Source: honolulu-intl frost station, USDA zone 12b, last updated 2026-06-28. Verify locally before planting high-value crops because microclimates, current weather, and yard exposure can move the safe date.

USDA zone 12b Honolulu frost station University of Hawaii Cooperative Extension Updated 2026-06-28

Read the method

Answer first

When to start radishes seeds indoors in Honolulu

In ZIP 96813, radishes is usually direct-sown around Dec 4 instead of started indoors.

Radishes is normally direct-sown in Honolulu. Use around Dec 4 as the outdoor planting window for ZIP 96813.

Seed starting schedule

Radishes dates for Honolulu, HI

Step	Date	How to use it
Direct Sow	December 4, 2025	Sow seed outside when the crop and soil can handle the window.

Last frost

When is the last frost in Honolulu?

Honolulu (ZIP 96813) has an average last spring frost around Jan 1.

First frost

When is the first frost in Honolulu?

The average first fall frost is around Dec 31, giving about 364 frost-free days.

Season map

Radishes windows by month

JanFebMarAprMayJunJulAugSepOctNovDec

Direct sow

Dec 4

Harvest

Jan 1

Frost watch

Dec 3

Reminder workflow

Every date has a next action

Direct sow radishesDec 4

Last frost windowJan 1

First radishes harvest windowJan 1

Last radishes sowing targetDec 3

Signal	Value	Why it matters
Last frost estimate	January 1, 2026	Warm-season transplant risk starts falling after this window.
First frost estimate	December 31, 2026	Fall planting counts backward from this date.
Season length	364 days	Longer seasons can support succession crops.
Spacing	1-2 in	Airflow and root space affect yield.
Soil temperature	40 F+	Seeds and transplants stall in cold soil.

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Local data

Why this date changes by ZIP

Honolulu frost history and USDA zone 12b shift the safe planting window. GrowZone uses a local representative station instead of one national rule.

University of Hawaii Cooperative 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

Radishes timing notes

Fast crop; harvest promptly before roots get woody. Radishes prefers full sun, 1-2 in spacing, and soil near 40 F+.

For fall, count backward from Dec 31. A conservative last sowing target is around Dec 3.