Dahlia
Dahlia spp.
Other names: Garden dahlia
Dahlias grow from tubers planted in spring and flower from midsummer until frost, in forms that range from small pompons to blooms 10 in (25 cm) across. The more you cut, the more they flower. In zones 7 and colder the tubers are lifted and stored over winter.
How to grow dahlia
Light
Full sun, with six to eight hours a day. In very hot climates, afternoon shade helps.
Watering
Do not water newly planted tubers until shoots appear, because they rot easily. Once plants are growing, water deeply two or three times a week.
Soil and feeding
Dig in compost before planting. Feed every three to four weeks from midsummer with a low-nitrogen fertilizer such as a tomato feed.
Planting and pruning
Plant after the last frost, once the soil reaches 60°F (15°C). Lay each tuber 4 to 6 in (10–15 cm) deep with the eye facing up, and push in a stake at the same time. Pinch out the tip above the third or fourth pair of leaves. Deadhead often.
Propagation
Divide tuber clumps in spring so that each piece has a section of old stem with at least one eye. In cold climates, lift the clumps after frost blackens the foliage and store them at 40 to 50°F (4–10°C) in barely moist peat-free compost or vermiculite.
Common problems
- Tubers rot before sprouting
- Cold, wet soil or watering too early. Wait for warm soil and do not water until growth shows.
- Ragged holes in petals and leaves
- Earwigs and slugs. Trap earwigs in upturned pots filled with straw and use iron phosphate bait for slugs.
- Lush plants with few flowers
- Too much nitrogen or too little sun.
Questions about dahlia
Do I have to dig up dahlias every year?
In zones 8 to 11 they can stay in the ground under a thick mulch. In colder zones the tubers freeze and must be lifted and stored.
When do dahlias bloom?
About eight weeks after planting, usually from July until the first frost.
Plant details
| Botanical name | Dahlia spp. |
|---|---|
| Family | Asteraceae |
| Native range | Mexico and Central America |
| Plant type | Bulbs. Tender tuberous perennial |
| Soil | Rich, well-drained soil |
| Flower color | Pink, red, orange, yellow, white, purple |
- Good cut flower
- Attracts pollinators
- Grows in containers
