When to Plant Sunflowers in Hawaii – 2026
Published: April 27, 2026
Hawaii sits in USDA Zone 12a (population-weighted primary). Plant sunflowers in Hawaii from March through July. Average last spring frost: Frost-free; first fall frost: Frost-free; frost-free growing season: 365 days. The bloom season for sunflowers is summer through fall.
Sunflowers Planting Dates in Hawaii
Direct sow sunflower seeds after last frost when soil reaches 10°C / 50°F. Most zones: April–June. Warm-season annual — does not tolerate frost. Days to bloom: 70–100 days from seed.
For Hawaii specifically, the recommended planting window is March through July. This window is based on the state's population-weighted USDA Zone 12a — but Hawaii spans multiple climate zones, so adjust based on your local conditions. Coastal, mountain, and inland areas within Hawaii can vary by 2 to 4 weeks from the state average. The 365-day frost-free growing season in Hawaii is tropical year-round. no frost history. hawaii and similar tropical locations.
Always check current local forecasts before planting frost-sensitive species. The 'last frost date' is an average — actual frost can occur 2 weeks after the average date in cold years. For warm-season annuals (petunias, zinnias, marigolds), wait at least 1 week past the average last frost date to ensure consistently warm soil. For cool-season annuals (pansies, snapdragons), planting 2 to 4 weeks before last frost is appropriate.
Best Sunflowers Varieties for Hawaii
For Hawaii Zone 12a, choose varieties rated for your zone or one zone colder for reliable performance. Below are the top sunflowers cultivars suitable for Hawaii's climate.
Single 30 cm (12 inch) heads on 3 m (10 ft) stalks. The classic giant sunflower. 90 days to bloom.
Branching habit, 1.5–2 m (5–7 ft) tall, multiple smaller blooms in red, orange, yellow, and bronze tones. 70 days.
Branching pale yellow blooms, 1.5–2 m (5–7 ft) tall. Excellent for cutting and pollinator gardens. 90 days.
Cut-flower industry standard. No pollen drop. Single bloom per stem. 50–60 days. Successive sowings every 2 weeks for continuous blooms.
60 cm (24 inch) tall, fully double yellow blooms. Container-friendly. 60 days.
How to Plant Sunflowers in Hawaii
Sow method for sunflowers: direct sow after last frost. The practical steps below apply to Hawaii's climate and the typical first-year planting timeline.
- →Direct sow sunflower seeds 2.5 cm (1 inch) deep, after the last frost when soil reaches 10°C (50°F).
- →Space giant varieties 60 cm (24 inches) apart; branching types 30 cm (12 inches); dwarf 20 cm (8 inches).
- →Choose a site with full sun (8+ hours) — sunflowers track the sun and lean toward shade.
- →Water consistently for the first 3 weeks; once established, water deeply weekly during dry periods.
- →Stake giant varieties at planting — adding stakes after the plant reaches 1 m (3 ft) damages roots.
- →Sidedress with balanced fertilizer when plants reach 60 cm (2 ft) tall — once is enough.
- →Successive sowings every 2 weeks from late spring through midsummer give continuous blooms through fall.
- →Harvest cut flowers when the bloom is fully open but the back of the head is still bright green; cut early in the morning.
Sunflowers Care Calendar for Hawaii
Spring (Hawaii last frost: Frost-free): The main planting window opens after last frost when soil reaches 10°C (50°F). For warm-season sunflowers, wait at least 1 week past last frost. Apply slow-release fertilizer at planting for first-season vigor.
Summer: Water consistently for the first month after planting; established plants need watering only during extended dry periods. Peak bloom for warm-season annuals.
Fall (Hawaii first frost: Frost-free): Final blooms before first frost — no fall planting recommended for warm-season annuals. Apply final mulch layer after first hard frost.
Winter: Mild winter conditions — many flowers continue blooming or remain semi-evergreen. Cool-season annuals (pansies, snapdragons) provide color through winter.
Frequently Asked Questions about Sunflowers in Hawaii
When should I plant sunflowers in Hawaii?
Plant sunflowers in Hawaii from March through July based on the state's primary USDA zone (12a). Direct sow sunflower seeds after last frost when soil reaches 10°C / 50°F. Most zones: April–June. Warm-season annual — does not tolerate frost. Days to bloom: 70–100 days from seed.
What USDA zone is Hawaii?
Hawaii spans multiple USDA zones, but the population-weighted primary zone is 12a. The state's average last spring frost is around Frost-free and first fall frost around Frost-free, giving a frost-free growing season of about 365 days. Adjust planting dates based on your specific local microclimate — coastal, mountain, and inland areas within the state can vary by 2 to 4 weeks from the state average.
Which sunflowers varieties grow best in Hawaii?
For Hawaii (Zone 12a), choose varieties rated for your zone or one zone colder for reliable winter survival. Mammoth (Russian Mammoth) (All zones) is widely planted across most US zones. Autumn Beauty mix is another strong choice (All zones). Match the variety to your specific microclimate and sun exposure for best results.