Root Vegetable

When to Plant Radishes in Hawaii

The fastest vegetable in the garden — some varieties are ready in just 25 days. Perfect for impatient gardeners and kids.

The Short Answer

In Hawaii, soil conditions are an important factor for radishes. Volcanic soils — extremely fertile but can be acidic. Excellent drainage on slopes. Varies dramatically by island and elevation. Direct sow 4 weeks before your last frost date. Radishes can also be planted in fall, 6 weeks before your first frost.

Hawaii Frost Dates

Your planting dates depend on which part of Hawaii you're in. Here are the frost date ranges by region:

Region	Zones	Last Frost (Spring)	First Frost (Fall)
Coastal Hawaii	11a, 11b, 12a, 12b, 13a	None	None
Upcountry/Mountain	10a, 10b, 11a	Rare	Rare

Radishes Planting Schedule for Hawaii

Coastal Hawaii (Zones 11a, 11b, 12a, 12b, 13a)

Average last frost: None · Average first frost: None

Direct Sow

4 wks before frost

Fall Planting

6 wks before first frost

Upcountry/Mountain (Zones 10a, 10b, 11a)

Average last frost: Rare · Average first frost: Rare

Direct Sow

4 wks before frost

Fall Planting

6 wks before first frost

Growing Radishes in Hawaii

Radishes in Hawaii's Climate

Sow radishes from November through January only. The window is brief. The good news: they're so fast-maturing (22-30 days) that you can get 3-4 succession plantings even in the shortest cool window.

Soil Considerations for Hawaii

Volcanic soils — extremely fertile but can be acidic. Excellent drainage on slopes. Varies dramatically by island and elevation. Loose, well-drained soil is especially important for radishes since the edible portion grows underground. If your soil is heavy clay, consider raised beds.

Hawaii Climate & Growing Season

Tropical. Year-round growing season at lower elevations. Elevation creates microclimates. Plant warm-season crops anytime. Radishes can handle frost well, which is an advantage in Hawaii's climate. You can push planting dates earlier in spring and extend into fall.

Growing season length varies across Hawaii: Coastal Hawaii (11a, 11b, 12a, 12b, 13a) has a last frost around None, while Upcountry/Mountain (10a, 10b, 11a) sees frost end around Rare. This difference matters for radishes — but radishes handle frost well, so the timing difference is less critical.

Growing Tips

Don't let them stay in the ground too long — they get pithy and hot. Succession plant every 2 weeks for continuous harvest.

Companion Planting

Plant radishes alongside these companions for better growth:

Peas Lettuce Carrots Spinach

The Bottom Line

Radishes can be grown successfully across Hawaii, but your exact planting dates depend on which region you're in. Coastal Hawaii gardeners should plan around a None last frost, while those in Upcountry/Mountain can typically plant later. For exact dates based on your zip code, use our free planting date finder.

Note: All dates are based on NOAA 30-year Climate Normals and represent historical averages, not predictions for any specific year. Always check your local weather forecast before planting frost-sensitive crops. Learn about our data sources.

Last reviewed: March 29, 2026