Chrysanthemums, or mums, are the classic autumn flower — and in Zone 11, autumn means the cooler months, when mild temperatures and shorter days trigger them to flower. Their great mounds of blooms in yellow, orange, pink, red and white are a highlight of a tropical winter garden, and they last for weeks, both on the plant and in a vase.
Mums are also one of the easiest flowers to grow from nursery plants, which makes them a good choice if you want colour without starting from seed. The planting calendar hub shows how Zone 11 timing works month by month, and our guide to when to plant asters in Zone 11 covers another cool-season flower that blooms alongside mums.
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 | 90–120 days |
| Sowing | both |
| Sun | full sun |
| Soil pH | 6.0–7.0 |
| Spacing | 12–18 inches |
| Water needs | moderate |
| Cold tolerance | hardy |
When to plant chrysanthemums in Zone 11
Plant chrysanthemums in Zone 11 in the cooler months, roughly November through February, when mild temperatures and shorter days trigger flowering. Mums are short-day plants: they flower when the nights get longer, which in the tropics happens in the cool season. Seed germinates in 7–14 days, and plants flower in 90–120 days, so an autumn sowing gives you blooms in the cool months. Most gardeners buy nursery plants in bud for faster colour. Zone 11 is frost-free, so there is no last frost date; check your local extension service and the forecast before planting.
Starting chrysanthemums in Zone 11
Start chrysanthemums from nursery plants in bud — the simplest route — or from seed sown indoors in trays. If you sow seed, transplant seedlings out when they have two sets of true leaves. Space plants 12–18 inches apart, and pinch out the growing tip when plants are a few inches tall, then pinch again a few weeks later, to encourage branching and a mound of flowers. Stop pinching once buds appear. Mums also grow well in pots, which lets you move them into shade in the hottest months. The seed-starting calculator can work out your sowing dates.
Soil, spacing, sun and water
Chrysanthemums need full sun and rich, well-drained soil with a pH of 6.0–7.0. Dig in plenty of compost before planting — mums are hungry feeders — and make sure drainage is good, as they hate wet feet. Water needs are moderate: water regularly, especially in dry spells, watering at the base rather than over the leaves, because wet leaves in humid weather invite disease. Feed every two weeks with a balanced liquid feed while buds are forming.
Companion planting
Good companions for chrysanthemums include lavender, marigolds, garlic and chives. Marigolds planted nearby deter soil pests, while lavender draws in the bees that visit mum flowers. Keep mums away from other heavy feeders that compete for nutrients, and give them space for airflow. The companion planting finder can suggest combinations for your whole garden.
Pests and problems
The common pests to watch for with chrysanthemums are aphids, slugs and thrips. Aphids cluster on young shoots and buds — wash them off with a strong jet of water. Thrips can distort flowers in hot weather, so check buds regularly and remove affected flowers. Slugs and snails chew seedlings at night in the wet season; protect young plants with a ring of coarse grit. Chrysanthemums contain a natural insecticide, pyrethrum, which deters many pests — one reason they are so trouble-free. If you are unsure what is damaging a plant, the pest identifier helper can narrow it down.
Harvest and storage
Harvest chrysanthemums 90–120 days after sowing, when the flowers open fully. Mums make excellent cut flowers: cut the stems in the morning, when they are fresh, and they will last up to two weeks in a vase — among the longest-lasting of all cut flowers. Deadhead spent blooms to keep plants flowering, and cut the whole plant back after flowering. In Zone 11, mums are usually grown as a cool-season display and replaced each year, though some varieties will regrow from the base in the coolest corners.
Why mums flower when the days get shorter
Chrysanthemums are short-day plants: they only start forming flower buds when the nights get long enough, which in most places happens in autumn. In Zone 11, near the equator, the day length changes very little through the year — but the cooler months still bring slightly longer nights, and that is usually enough to trigger flowering, especially in varieties bred for warm climates. If your mums grow tall and leafy but never flower, the nights may not be long enough, or artificial light at night may be interrupting the dark period — mums need uninterrupted darkness to set buds, so keep them away from bright garden lights. Choose varieties bred for tropical conditions, and plant them where the nights are truly dark.
Frequently asked questions
When should I plant chrysanthemums in Zone 11?
Plant in the cooler months, roughly November through February, when mild temperatures and shorter days trigger flowering. Seed germinates in 7–14 days and plants flower in 90–120 days.
Why are my mums tall and leafy with no flowers?
Usually nights that are too short, or artificial light interrupting the dark period. Mums need long, uninterrupted nights to set buds — keep them away from bright garden lights.
How long do cut chrysanthemums last?
Up to two weeks in a vase — among the longest-lasting of all cut flowers. Cut stems in the morning and change the water every few days.
Will mums come back next year in Zone 11?
Sometimes, in the coolest corners. Most gardeners treat mums as a cool-season display and buy fresh plants each year.