Hawaii planting calendar

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

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

Rosemary planting timetable for Hawaii

Stage	When in Hawaii	Anchor
Direct-sow / set out (spring crop)	late January — early March	Frost-free — plant as soon as nights stay above 10 °C
Spring-crop harvest	~90 days later, before peak summer heat	90-day crop — finishes before mid-summer
Plant the fall crop	mid-August (August 15) — once the worst heat breaks	~104 days before the first fall frost (no frost)
Fall-crop harvest	mid-November into early winter	90-day crop — often the more productive of the two

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 rosemary dates

Hawaii's long hot summer shuts down fruit set, so locals run two short crops — a spring planting and a fall planting — around a deliberate mid-summer pause, instead of one long northern-style season. Hawaii is frost-free at sea level and tropical year-round. Elevation, rainfall, and microclimate matter far more than any cold zone.

Start seeds indoors 10–12 weeks before the last frost; germination is slow and erratic (14–21 days at 18–21 °C / 65–70 °F) with low viability, so propagation by stem cuttings is preferred by most Extension services. Transplant outdoors after the last frost once soil has warmed — rosemary is perennial only in USDA zones 7–10 (established plants survive to about −12 °C / 10 °F); in zones 6 and colder treat as a tender annual or overwinter potted plants indoors before the first autumn frost. Tip harvests of stem ends begin around 80–100 days from transplant.

Frost-risk note

Frost is essentially absent — the limiting hazard here is summer heat, when rosemary plant pollen goes sterile above ~32 °C.

Regional variation within Hawaii

the coastal lowlands of all islands (zone 13a) can start the spring crop weeks earlier and may garden almost year-round; the upper slopes of Mauna Kea and Haleakala (zone 9a) runs a shorter, more northern-style single season.

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

Pair the spring slot with other heat-lovers (peppers, squash, beans); use the cool October–February window for greens and brassicas.

Quick-grow guide

Sun: Full sun — 6+ hours direct.
Soil temperature for germination: 18–21 °C (65–70 °F).
Spacing: 18–36 inches (45–90 cm) between plants.
Days to harvest: ~90 days from planting out.

Frequently asked questions

When is the best time to plant rosemary in Hawaii?

In Hawaii (mostly USDA zone 12b), set the spring crop out late January–March, harvest before peak summer heat, then plant a second crop mid-August for an autumn harvest. Avoid mid-summer. Rosemary are half-hardy — young plants shrug off a light frost but not a hard freeze, so sowing can start a couple of weeks before the last spring frost.

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 rosemary in Hawaii?

Yes. Hawaii's dominant zone 12b supports rosemary — the key is timing. Rosemary are half-hardy — young plants shrug off a light frost but not a hard freeze, so sowing can start a couple of weeks before the last spring frost.

Does the planting date change across Hawaii?

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

Pair the spring slot with other heat-lovers (peppers, squash, beans); use the cool October–February window for greens and brassicas.

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.