Sunflowers are pure joy in a Zone 11 garden: tall, fast and unmistakable, turning their great gold heads to follow the sun. They love heat, grow astonishingly quickly in tropical soil, and give you flowers, seeds and a magnet for bees all in one plant. Children love them, pollinators love them, and a row of sunflowers along a fence is one of the simplest ways to make a garden feel alive.
Sunflowers are also one of the easiest flowers to grow from seed, which makes them a perfect first flower for a new gardener. The planting calendar hub shows how Zone 11 timing works month by month, and our guide to when to plant zinnias in Zone 11 covers another fast, heat-loving annual for the same sunny bed.
Zone 11 at a glance
USDA Zone 11 covers the warmest, most tropical parts of the United States — Hawaii, southern Florida, Puerto Rico and the warmest coastal pockets. Winters are warm, with average winter lows of 40 to 50°F, and the growing season never really ends.
Zone 11 is frost-free year-round: there is no average last spring frost and no average first autumn frost. That means you plant by heat and by the wet and dry seasons, not by frost dates. These are USDA zone averages, not exact figures for any one garden — always check your local extension service and the forecast before planting.
| Detail | Zone 11 guidance |
|---|---|
| Average winter low | 40 to 50°F |
| Average last spring frost | Frost-free (no frost dates) |
| Average first autumn frost | Frost-free (no frost dates) |
| Days to germination | 7–14 days |
| Days to maturity | 70–90 days |
| Sowing | direct sow |
| Sun | full sun |
| Soil pH | 6.0–7.5 |
| Spacing | 18–24 inches |
| Water needs | moderate |
| Cold tolerance | tender |
When to plant sunflowers in Zone 11
Plant sunflowers in Zone 11 in the warm months, when the soil is warm and the days are long — spring through early summer is ideal, with a second sowing in late summer for autumn flowers. Avoid sowing in the wettest weeks, when seed can rot before it sprouts. Seed germinates in 7–14 days, and plants flower in 70–90 days, so a spring sowing gives you towering blooms by midsummer. Succession-sow every two to three weeks for a continuous display. Zone 11 is frost-free, so there is no last frost date; check your local extension service and the forecast before sowing.
Starting sunflowers in Zone 11
Start sunflowers from seed sown directly where they are to flower — sunflowers hate transplanting, because their long taproot is easily damaged. Sow two seeds per spot, about an inch deep, and thin to the strongest seedling once they are a few inches tall. Tall varieties need a sheltered spot or a stake: a six-foot sunflower in a tropical storm is a sail. Dwarf varieties suit pots and windy spots. Space plants 18–24 inches apart, and give them the sunniest place in the garden. The seed-starting calculator can work out your sowing dates.
Soil, spacing, sun and water
Sunflowers need full sun and deep, fertile, well-drained soil with a pH of 6.0–7.5. They are heavy feeders — dig in plenty of compost before sowing, and feed tall varieties once or twice as they grow. Water needs are moderate, but young plants need regular watering until established, and tall varieties need deep watering in dry spells to keep their great heads upright. Mulch around the base to hold moisture and keep the roots cool, but keep the mulch away from the stem.
Companion planting
Good companions for sunflowers include lavender, marigolds, garlic and chives. Marigolds planted at the base deter soil pests, while lavender draws in the bees that pollinate sunflowers. Sunflowers make a useful windbreak and living trellis for climbing beans — though they can shade smaller neighbours, so plant them on the north side of a bed. The companion planting finder can suggest combinations for your whole garden.
Pests and problems
The common pests to watch for with sunflowers are aphids, slugs and thrips. Aphids cluster on young shoots and under leaves — wash them off with a strong jet of water. Slugs and snails chew seedlings at night in the wet season; protect young plants with a ring of coarse grit. Birds love sunflower seed, so net the heads as they ripen if you want the seed for yourself. If you are unsure what is damaging a plant, the pest identifier helper can narrow it down.
Harvest and storage
Harvest sunflowers 70–90 days after sowing. For cut flowers, cut the stems in the morning when the first petals open, and they will last about a week in a vase. For seed, wait until the back of the head turns yellow-brown and the seeds are plump and striped, then cut the head and hang it upside down in a dry, airy place. Rub the seeds out once dry, and roast them or save them for sowing. Leave a few heads for the birds — they will thank you, and the garden will be livelier for it.
Growing giant sunflowers in Zone 11
If you want a truly giant sunflower, choose a variety bred for height, such as Mammoth, and give one plant the royal treatment: the sunniest spot, deep compost, regular deep watering, and a strong stake from the start. Thin ruthlessly — one plant per spot, with no competition. Feed with a balanced fertiliser every two weeks once the plant is knee-high. In Zone 11's long warm season a Mammoth can reach ten feet or more, but it will need shelter from tropical storms, so plant it against a fence or wall on the sheltered side. Measure it, photograph it, and let the children claim the record.
Frequently asked questions
When should I plant sunflowers in Zone 11?
Sow in the warm months, spring through early summer, with a second sowing in late summer. Seed germinates in 7–14 days and plants flower in 70–90 days.
Can I transplant sunflower seedlings?
It is best not to — sunflowers grow a long taproot that is easily damaged by transplanting. Sow directly where they are to flower.
Why is my sunflower head drooping?
A heavy head drooping is normal as seed ripens, but a young plant drooping usually means thirst. Water deeply at the base and mulch to hold moisture.
How do I keep birds from eating my sunflower seeds?
Net the heads with fine mesh as soon as the seeds start to plump. Leave one or two heads un-netted for the birds.