Dahlia plants are easy to grow, giving you late summer colour when many other plants are past their best. Whether you want flowers for cutting or flowers for a pot by your back door there will be a dahlia to suit most places! Single-flowered varieties will also attract bees.
Staking Dahlias – Tall Dahlias are prone to flopping over and are easily damaged by the wind. Some timely stakes inserted early in the season will prevent this happening! Insert stakes when planting your Dahlias, either using bamboo canes (canes and string if grown in rows) or twiggy sticks for a more natural look. You can also use garden obelisks to support your growing Dahlias, placing the obelisk directly over the Dahlia plant. The supports may look untidy initially, but your Dahlias will soon grow to cover them. When tying in your Dahlias make a figure of eight with the string to prevent the stems rubbing against the canes.
However if all the messing about with stakes is too much bother, in this video there are some good tips about how to top your dahlias to make them stronger and to keep them from flopping.
Taking Dahlia cuttings
Where to grow dahlias
Dahlias perform best in a rich, fertile, well-drained soil in full sun. They are heavy feeders so before planting, dig in plenty of well-rotted manure or compost and top-dress with a general purpose fertiliser. Dahlias are half-hardy so will need protection from frosts.
Seeds, tubers or potted plants?
Dahlias can be grown from seed, dormant tubers or planted as pot-grown plants. If growing Dahlias from seed, sow them between February and April. If growing Dahlias from tubers, plant them from April to May. Potted Dahlias are planted out in May and June. Space taller varieties about 60cm (24″) apart, medium sized varieties 45cm (18″) apart, and dwarf bedding varieties 30cm (12″) apart.
How to grow Dahlias from tubers
When growing Dahlia tubers, plant them directly in the ground from around mid-April. Don’t worry about frosts as the soil will insulate them. Prepare a planting hole that is 10-15cm (4-6″) deep, and wide enough to accommodate the Dahlia tuber comfortably. Place the Dahlia tuber inside with the ‘eye’ (where the tubers meet – often with remnants of last year’s stems) facing upwards. Backfill with the remaining soil, gently firming as you go and water the tubers in thoroughly. Tubers can also be potted up in April and grown on in a greenhouse for a head-start; planting out after all risk of frost has passed.
- Pinching out – Pinching out Dahlias once they reach 40cm (16″) tall encourages branching and more flowers. Simply pinch off the growing shoot just above a set of leaves. Dahlias can be further pinched once side-shoots develop. For giant blooms however, it’s best to only allow between three and five flower stems to develop.
- Feeding – Once flowers appear on your Dahlia plants, feed them with a high potash liquid fertiliser, such as tomato feed every two weeks until early September. Feeding Dahlias will encourage more flowers.
- Dead-heading – Dead-head Dahlia flowers as they fade to encourage more blooms to be produced. Simply pinch or cut the flower stem back to a pair of leaves to keep the plant looking tidy.