Zone 12b: Gardening in Honolulu and Hawaii's Warm Coasts
Zone 12b is warm, frost-free lowland Hawaii, including Honolulu, Kaneohe and Kailua-Kona. Tropical fruit such as banana and papaya thrives. Cool-season vegetables are mostly winter crops at low elevation, and wind, rainfall and heat shape the garden more than any winter cold.
- Coldest winter night
- 55 to 60°F
- ZIP codes in the zone
- 61
Frost in zone 12b
In 100% of zone 12b's ZIP codes with weather records, a 32°F night happens in fewer than half of years, so frost dates do not organize the gardening year. Cool-season vegetables grow from fall through spring, and heat, not frost, ends the season for many crops. Use the planting calendar for your region: Hawaii (low elevation).
What a zone 12b winter means
In zone 12b nothing freezes, and cold never limits what grows. The hardiness zone tells you only that tender tropical plants are safe outdoors; for choosing plants, what matters is heat, rainfall, wind and salt. CTAHR stresses that Hawaii’s microclimates change over short distances, so a windward Kaneohe garden and a dry leeward Kona garden in the same zone need different plants and watering.
Where zone 12b is
Zone 12b covers urban Honolulu and much of the south and east shore of Oahu, windward Oahu around Kailua and Kaneohe, the Kona coast of the Big Island around Kailua-Kona, and other low, warm coastal areas of the islands.
Fruit
- Bananas thrive with warmth, full sun and plenty of rain; CTAHR advises planting them in sheltered spots because wind tears leaves and topples plants.
- Lychee is less dependable without a cool winter (see the FAQ).
Vegetables
Treat winter as the season for cool-season crops. CTAHR’s trials show head lettuce succeeds at low elevations only in winter, while leaf lettuces manage year-round at many lowland sites, and heat-tolerant broccoli cultivars such as ‘Greenbud’ and ‘DeCicco’ are the ones for warm lowlands. CTAHR’s home garden bulletin names carrots, beets, chard, mustard greens, eggplant, green onions and beans as dependable year-round crops at low and medium elevations, with broccoli and cabbage best in winter and tomatoes doing best in the cooler season. Okra is a good warm-season crop.
Special concerns
- Siting: a University of Hawaii Extension agent notes that the south side of a house gets the most intense sun and the north and east sides the most wind, so the southwest side is often the best spot.
- Windbreaks: sorghum-sudangrass can grow into a 6-foot windbreak in about 40 days.
- Water: CTAHR advises against growing vegetables without irrigation in most of Hawaii, since even frequent showers may not add up to enough rain. Organic mulch reduces drought damage and the need to irrigate.
- Soil: CTAHR recommends a pH of 5.5-6.5 for most vegetables and working compost or manure into the top 6-8 inches before planting.
Where zone 12b is
States with zone 12b ZIP codes, the largest first: Hawaii.
Largest cities in zone 12b
Zone 12aZone 13aAll zones and the zone finder
Questions
Can I grow lettuce in Honolulu?
Yes, best in the cooler months. University of Hawaii CTAHR found head lettuce grows only in winter at low elevations, while leafy types grow year-round at many lowland sites. High night temperatures make lettuce bitter.
Which broccoli grows in Hawaii's lowlands?
CTAHR recommends heat-tolerant cultivars such as 'Greenbud' and 'DeCicco' for warm lowlands, and keeps types such as 'Waltham 29' for cool uplands above 2,000 feet.
Does lychee fruit in zone 12b?
Less reliably than in cooler areas. CTAHR says lychee needs a cool, dry winter, around 59°F days and 50°F nights, to start flowers. Warm coastal sites may not give it that every year.