Hawaii planting calendar

When to plant collard greens in Hawaii — sow, transplant & harvest dates

Hawaii is mostly USDA zone 12b (range 9a-13a). Dates below are derived from collard greens's frost tolerance and Hawaii's frost window — not generic national averages.

Collard Greens planting timetable for Hawaii

Stage	When in Hawaii	Anchor
Direct-sow / set out (main)	October — February	Grown through the cool season, not summer
Shoulder sowing	September and again late February	Avoid germinating into summer heat
First harvest	~70 days after sowing (late autumn through spring)	70-day crop

Dates are state-wide averages for the dominant zone. Local microclimates — elevation, urban heat, coastal moderation — can shift the window by 1-2 weeks. Use the frost-date calculator for a date tuned to your town.

Why Hawaii's climate shifts the collard greens dates

Hawaii flips the calendar: its winter is the productive collard greens season while northern states are frozen, and its summer is the off-season. Hawaii is frost-free at sea level and tropical year-round. Elevation, rainfall, and microclimate matter far more than any cold zone.

Collards are one of the hardiest brassicas, tolerating temperatures down to about -7 °C once established, and one of the most heat-tolerant — unlike kale or cabbage, they continue producing in summer heat above 32 °C, which is why they are a staple in Zones 7–9 year-round. Transplant 2–4 weeks before last spring frost, or direct-sow where the season allows; for a fall harvest, start transplants 8–10 weeks before first fall frost. Succession-plant for continuous leaf harvest.

Frost-risk note

Frost is essentially a non-issue here — heat, not cold, ends the crop.

Regional variation within Hawaii

the coastal lowlands of all islands (zone 13a) can sow earliest in autumn and latest into late winter; the upper slopes of Mauna Kea and Haleakala (zone 9a) has a slightly shorter, frost-bracketed window.

Honolulu — USDA zone 12b
Hilo — USDA zone 12a
Kailua-Kona — USDA zone 12b
Lihue — USDA zone 12b

What else to plant in Hawaii around then

The same cool window suits other greens, brassicas, peas, carrots, and radishes — fill beds October through February.

Quick-grow guide

Sun: Full sun — 6+ hours direct.
Soil temperature for germination: 7-29 °C (45-85 °F).
Spacing: 18-24 inches (45-60 cm) between plants.
Days to harvest: ~70 days from planting out.

Frequently asked questions

When is the best time to plant collard greens in Hawaii?

In Hawaii (mostly USDA zone 12b), grow collard greens as a cool-season crop: direct-sow from October through February, harvest ~70 days later, and skip summer entirely — heat above 24 °C bolts it. Collard Greens are cold-hardy — they tolerate frost and actively prefer cool weather, so they go in well before the last spring frost and bolt in summer heat.

What USDA zone is Hawaii?

Most of Hawaii sits in USDA hardiness zone 12b, with the state spanning roughly 9a-13a from the upper slopes of Mauna Kea and Haleakala (zone 9a) to the coastal lowlands of all islands (zone 13a). The last spring frost averages no frost and the first fall frost no frost.

Can you grow collard greens in Hawaii?

Yes. Hawaii's dominant zone 12b supports collard greens — the key is timing. Collard Greens are cold-hardy — they tolerate frost and actively prefer cool weather, so they go in well before the last spring frost and bolt in summer heat.

Does the planting date change across Hawaii?

What else can I plant in Hawaii around the same time?

The same cool window suits other greens, brassicas, peas, carrots, and radishes — fill beds October through February.

Source and methodology

State zone spans from the USDA Plant Hardiness Zone Map (2023); frost-date averages from NOAA Climate Data Online. Hot-state two-season timing cross-checked against the UF/IFAS Florida Gardening Calendar and the University of Arizona Cooperative Extension planting calendar. Curated by the Growli editorial team.