The New Almanac

USDA Zone 12b

Zone 12 · The True Tropics

Average annual extreme minimum temperature: 55 to 60 °F (12.8°C to 15.6°C).

Hawai'i's warm lowlands and most of Puerto Rico — 50 to 60°F winter minimums, a band the USDA map only added in 2023. The garden never closes; elevation and rainfall write the calendar that frost no longer does.

By the numbers

Median season
Year-round
ZIPs tracked
101

Medians across every ZIP we track in zone 12b, derived from NOAA 1991–2020 climate normals. Look up your own ZIP for local dates — within a zone, frost varies by weeks.

Where you'll find zone 12

Hawai'i's settled lowlands — nearly two-thirds of Hawai'i ZIPs in our data are 12b — and a wide share of Puerto Rico. Zone 12 (with 13) was added in the 2023 USDA map update to describe places whose average winter lows never approach freezing.

Vegetables that earn their keep

  • Everything, year-round, by elevation (CTAHR): cool-season broccoli and cabbages are "excellent garden crops at low elevations during winter, and at high elevations thrive the year around"
  • Warm-season crops (okra, New Zealand spinach) in the warm lowlands (CTAHR)
  • Variety choice is elevation choice: CTAHR matches lowland vs. >2,000 ft varieties for the same crop

Fruits & perennials that overwinter

  • Papaya in the low, warm belt (min temps above 60°F — CTAHR)
  • Mango, avocado, banana — the standing tropical roster (UF/CTAHR)
  • Chill-requiring temperate fruit: not applicable — there is no chill

Elevation is the new season

CTAHR's central insight for tropical gardening: what latitude and month do elsewhere, altitude does here. Cool-season vegetables that fit only the winter window at sea level thrive all year above 2,000 feet. Hawaiian seed guidance lists different varieties of the same crop for lowland versus upland gardens — choosing a variety here is choosing a climate.

Multiple harvests, multiple plantings

With day temperatures riding 65–78°F through summer, crops develop fast and beds turn over several times a year (CTAHR). Succession planting isn't a technique for stretching the season — it is the season.

What the rain decides

Drainage and irrigation replace frost dates as the planning axis. Papaya wants about 4 inches of water a month at minimum, and leeward (dry-side) plantings need irrigation while windward gardens fight fungal disease — Phytophthora and anthracnose thrive in still, humid air, so spacing and airflow are disease control (CTAHR).

The pest treadmill

CTAHR's blunt summary holds: insect and disease enemies "must be fought continuously." Year-round warmth means year-round generations. Resistant varieties, sanitation, and windbreaks (established before plantings, not after) are the standing infrastructure of the tropical garden.

Plant guides, timed to your frost dates

Every guide gives its planting calendar relative to your last frost — the dates above (or your ZIP's) drop straight in.

Sources