Bulb
Dahlia
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Flowers | Flowers in July | Flowers in August | Flowers in September | Flowers in October | ||||||||
| Plant | Plant in May | Plant in June | ||||||||||
| Looks good | Looks good in July | Looks good in August | Looks good in September | Looks good in October |
Overview
Dahlias are the powerhouses of late summer, flowering non-stop from July until the first hard frost. The range is huge: dinner-plate types like 'Café au Lait', neat pompons, spiky cactus forms, and dark-leaved 'Bishop of Llandaff' with scarlet single flowers. Open-centred singles and collarettes, such as 'Bishop of York' or 'Honka', are the ones to choose for bees, as tightly double flowers hide their pollen.
Where to grow dahlia
A sunny, sheltered spot with rich soil gives the best plants. Dahlias suit mixed borders, cutting patches on the allotment and large containers. Dwarf bedding types work in pots and window boxes.
Planting
Start tubers in pots indoors in March or April, then plant out in late May or June when frost risk has gone, a little earlier in mild south-western gardens. Set tubers about 10cm deep, with a stake in place for tall varieties. Mix well-rotted manure into the planting hole.
Care through the year
Spring
Pot up tubers and pinch out the growing tips once shoots have three pairs of leaves to encourage bushier plants.
Summer
Water deeply in dry spells, feed with a high-potash fertiliser weekly and deadhead faded blooms. Tie stems to stakes as they grow.
Autumn
Once frost blackens the foliage, cut stems to 15cm. Lift tubers in cold or wet gardens, or mulch them deeply where winters are mild.
Winter
Store lifted tubers in dry compost in a frost-free shed or garage. Check monthly for rot.
Pruning
Pinch out the tips of young plants and deadhead regularly; spent flowers are pointed, while new buds are round.
Propagation
Divide tubers in spring, making sure each piece has part of the old stem with a bud. You can also take basal cuttings from shoots of tubers forced into growth under cover in early spring.
Common problems
Slugs and snails devour young shoots, so protect new plants with barriers and evening patrols. Earwigs nibble petals; trap them in upturned pots stuffed with straw. Aphids, capsid bugs and powdery mildew appear in summer. Tubers rot in cold, wet soil over winter.
Guides to the problems most likely to affect dahlia:
Something else wrong? Diagnose it by symptom.
Month-by-month reminders
Jobs for this plant come round in May and June. Each month page lists everything else worth doing in the garden at the same time.
Related plants
Sources
Botanical names follow Kew's Plants of the World Online; growing attributes were checked against the references below. Text is our own. See our editorial policy.