Dahlia vs Chrysanthemum: Tubers Versus Perennials
The dahlia vs chrysanthemum difference starts below ground. NC State Extension notes that dahlia tuberous roots can be injured below 25°F, so they are often grown as annuals. Iowa State University Extension describes garden mums as fall bloomers that flower as nights get longer in late summer.
The short answer
Dahlias grow from tender tuberous roots. In zones below 7, dig them in fall plus store them through winter. Garden mums are perennials that bloom in early fall in response to long nights. Both like full sun plus well drained soil, but each needs different care through winter.
How do the roots differ?
NC State Extension notes that dahlias grow from tuberous roots planted 3 inches deep. Propagation happens by division or root cutting.
Garden mums are perennials that form erect mounds 1 to 3 feet tall plus 1 to 2 feet wide. Iowa State University Extension notes that they can be grown as perennials planted in spring or as annuals planted in fall.
| Trait | Dahlia | Garden mum |
|---|---|---|
| Root type | Tender tuberous roots | Perennial crown |
| Bloom time | Late summer to first frost | Early fall |
| Winter care | Dig below zone 7 | Mulch in place |
Source: NC State Extension plus Iowa State University Extension.
When does each bloom?
NC State Extension notes that dahlias bloom from late summer to first frost when mulched plus well watered. Deadheading spent flowers prolongs blooming.
Iowa State University Extension explains that mums are short day plants. They form flower buds as days shorten plus nights lengthen in late summer. Light at night, such as a street light, can delay flowering.
How are they overwintered?
Iowa State University Extension advises cutting dahlias back to 2 to 4 inches within three or four days of a killing frost. Leave them in the ground six or seven more days, then dig them carefully. Store the clumps in a cool, dry place at 40 to 50°F.
For mums, Iowa State University Extension notes that spring is the ideal time to plant. Those planted in late summer or early fall often do not survive the winter.
How to: step by step
- Plant both in full sun with well drained soil.
- Set dahlia tubers 3 inches deep after frost.
- Stake tall dahlias as they rise.
- Pinch mums when new shoots reach 6 inches.
- Stop pinching mums by early July.
- Dig dahlias after a killing frost in cold zones.
Troubleshooting
Dahlia tubers rot: wet soil. NC State Extension calls for moist but well drained soil.
Leggy, floppy mums: no pinching. Iowa State University Extension advises pinching 2 or 3 times in spring plus early summer.
Few dahlia blooms: low sun or no deadheading. Provide full sun plus remove spent flowers.
For related reading see leaf anatomy, bees in outdoor gardens plus garden layout planning. Kind Seed Co also stocks cannabis seeds.
Sources
- Dahlia, NC State Extension Gardener Plant Toolbox
- How do I overwinter dahlias?, Iowa State University Extension, Yard plus Garden
- Growing chrysanthemums in Iowa, Iowa State University Extension
- Chrysanthemum x morifolium (garden mum), NC State Extension Gardener Plant Toolbox
FAQ
Are dahlias perennials?
Dahlias are tender perennials. NC State Extension notes that they are most often grown as annuals, since their tuberous roots can be injured below 25°F. In zones 7 to 10, mulch them over in winter. In colder zones, dig the tubers in fall plus store them at 35 to 45°F.
Do mums come back every year?
Garden mums can, according to Iowa State University Extension, which notes they are more cold hardy than florist mums. Mums planted in spring have the most success. Those planted in late summer or early fall often do not survive the winter. Most florist mums will not survive winter outdoors in Iowa.
Why are my mums blooming late?
Iowa State University Extension explains that mums need long nights to bloom. Anything that interrupts the night, such as a street light, can delay flowering or stop it. Pinching after early July can also delay flowering, so finish pinching by Independence Day.
Can both grow in pots?
Yes. NC State Extension notes that dahlias are at home in container gardens, plus small potted dahlias are sometimes used as florist plants. NC State also lists mum types such as cascades plus charms that are grown as pot plants. Give pots full sun plus good drainage.
Do dahlias need staking?
Often. NC State Extension notes that dahlias tend to be tall plus may require staking. Set stakes at planting so the tubers are not damaged later. Plants that stay mulched plus well watered give a long bloom season from late summer to first frost.
