Chrysanthemums, or mums, are the classic autumn flower: just as the garden is fading, they produce masses of blooms in every colour from white and yellow to deep red and bronze, in shapes from simple daisies to elaborate pompons. They are the flower of the autumn border, the porch pot and the vase, and they are far easier to grow than their showy flowers suggest.
The key to chrysanthemums is light. They are short-day plants, which means they flower as the days shorten in autumn, and any artificial light at night can delay or prevent flowering — so do not plant them under a security light. They are hardy perennials in most zones, coming back year after year, and a yearly pinch in early summer keeps them bushy instead of leggy.
Chrysanthemums at a glance
| Growing factor | What chrysanthemums need |
|---|---|
| Sun | full sun |
| Soil pH | 6.0–7.0 |
| Days to germination | 7–14 |
| Days to maturity | 90–120 |
| Spacing | 12–18 inches apart |
| Water needs | moderate |
| Cold tolerance | hardy |
| Family | Asteraceae |
Starting seeds
Chrysanthemums give you a choice: start seeds indoors for earlier flowers, or sow direct once the soil warms. For the earliest display, sow indoors a few weeks before your last frost — late winter in Zones 3–5, early spring in Zones 6–8, late winter in Zones 9–10 — and transplant out after the frosts end. For direct sowing, wait until the soil is workable and warming: late spring in Zones 3–5, mid-spring in Zones 6–8, early spring in Zones 9–10. Zones 11–13 are frost-free, so both methods work through much of the year; check your local extension service for the best local dates. Seeds germinate in 7–14 days. Keep seed mix or soil evenly moist until seedlings are up, and give indoor seedlings as much light as you can. Our seed starting calculator plans your indoor sowing date, and the germination time calculator estimates when to expect seedlings.
Transplanting and planting out
Transplant seedlings out after the last frost, on a cloudy day or in the evening so they do not wilt in the sun. Space plants 12–18 inches apart — that spacing is what keeps air moving and disease down — and water each plant in well. Our plant spacing calculator works out exactly how many plants fit your bed, and the square foot garden planner helps lay them out.
Soil and feeding
Chrysanthemums grow best in fertile, well-drained soil with a pH of 6.0–7.0. Dig in compost before planting — it feeds the soil and helps it hold moisture without getting soggy — and mulch after planting to keep the roots cool and the weeds down. Feed during the growing season with a balanced fertiliser at the label rate, roughly once a month while plants are actively growing, and stop feeding as the season ends. Our fertiliser calculator works out the right amount for your bed, and the compost ratio calculator helps you make good compost to dig in.
Watering
Chrysanthemums have moderate water needs: keep the soil evenly moist while plants are establishing and flowering, and water deeply rather than little and often so the roots grow down. Water at the base in the morning so the foliage dries during the day, mulch to hold moisture in, and watch for wilting in hot, dry spells. Our watering calculator gives a starting point for your bed size, and the watering schedule generator can build a routine around it.
Sunlight and temperature
Chrysanthemums need full sun — at least six hours of direct sun a day. Chrysanthemums are hardy and tolerate frost and cold weather well, so they can be planted out earlier and left in the ground over winter in most zones. In frost-free Zones 11–13, heat and a lack of winter chill can limit performance, so give them the coolest spot you have. Check your zone with the hardiness zone finder before choosing varieties. Our sunlight calculator can check whether your spot gets enough sun.
Pests and diseases
The pests and diseases to watch for on chrysanthemums are aphids, slugs, thrips. Aphids can cluster on buds and shoot tips, slugs may eat young shoots, and thrips can mark the petals in hot weather. Good air flow and morning watering prevent most disease problems. Check plants weekly, looking under leaves as well as on top, and act early. Hand-pick larger pests, knock aphids off with a strong spray of water, and remove badly affected leaves. Keep the area weed-free and avoid wetting the foliage when you water, since damp leaves invite fungal disease. Our pest identifier helper can help identify what you are seeing, and the plant disease checker helps narrow down leaf and stem problems.
Companion plants
Good companions for chrysanthemums are lavender, marigolds, garlic, chives. Lavender, marigolds, garlic and chives are good companions, and mums pair well with asters and ornamental grasses for a late-season display. Our companion planting finder can suggest more pairings for your bed plan.
Harvesting
Cut chrysanthemums for the vase when the flowers are almost fully open — unlike many flowers, mums open well in water, so you can cut them a little early. Cut in the morning, strip the lower leaves, and put stems straight into water: they last two weeks or more, longer than almost any other cut flower. Deadhead spent blooms to keep the plant tidy, and in late autumn cut the stems down after the first frosts, mulching the crown for winter. Our harvest date calculator can estimate your picking date from your sowing date, and the vegetable yield estimator helps you work out how much a bed will produce.
Common problems and fixes
| Problem | Likely cause | Fix |
|---|---|---|
| No flowers in autumn | light at night, or pruned too late | Keep mums away from artificial light and stop pinching by midsummer. |
| Leggy plants with few flowers | never pinched, or too much shade | Pinch young plants in spring and early summer, and give full sun. |
| Leaves turn yellow and drop | overwatering or poor drainage | Water at the base and improve drainage. |
No flowers in autumn
Chrysanthemums flower as days shorten, so a security light or porch light shining on them at night can stop them flowering altogether. Plant them where nights are dark, and stop pinching the plants by midsummer so they have time to set buds.
Leggy plants with few flowers
A mum that is never pinched grows into a few tall, bare stems with flowers only at the top. Pinch the tips out several times in spring and early summer, stopping by midsummer, and the plant will branch into a bushy shape covered in flowers.
Leaves turn yellow and drop
Mums hate wet feet, and leaves that yellow and drop from the base usually mean the soil is staying wet. Water at the base in the morning, improve drainage with grit or compost, and never let pots sit in a saucer of water.
Frequently asked questions
How long does it take to grow chrysanthemums?
From planting to maturity takes 90–120 days. Seed germination takes 7–14 days, and the total time depends on whether you start from seed, a nursery plant, or a bulb or cutting.
How far apart should I plant chrysanthemums?
Space chrysanthemums 12–18 inches apart. That spacing gives each plant room for air movement, which keeps disease down, and room to reach its full size without crowding its neighbours.
What soil pH do chrysanthemums need?
Chrysanthemums prefer a soil pH of 6.0–7.0. Test your soil before amending it — most garden soils are close enough, and guessing with lime or sulphur can do more harm than good.
Are chrysanthemums perennials?
Yes, garden mums are hardy perennials in most zones and come back year after year. Florist mums sold in pots in autumn are often less hardy, so plant garden varieties if you want them to return.
When should I plant chrysanthemums?
Plant in spring for the strongest plants, so they have a full season to establish before flowering in autumn. Autumn-planted mums can work in mild zones, but they need time to root before winter.