How to grow dahlias from tubers
Find out how to grow dahlias from tubers, in our step-by-step guide.
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There are three ways to grow dahlias: from tubers, rooted cuttings or seed.
Tubers are the roots of mature plants and look like a cluster of brown, carrot-like roots joined by the previous year's dried stem. You can buy them from garden centres or by mail order in spring, or use your own tubers that have been overwintered.
- Buy dahlia tubers from Thompson & Morgan, Suttons, and Crocus.
When to plant dahlia tubers
Starting dahlias in pots is a great way to get them into growth earlier in the season. Simply plant dahlia tubers in large pots filled with peat-free, multi-purpose potting compost in March or early April, and then keep them on a windowsill or in a frost-free greenhouse until late May, when it's safe to plant them outside.
Starting off dahlia in pots will also encourage them to develop more quickly, so they're likely to start flowering earlier. Before planting, soak the tubers in a bucket of tepid water for an hour so they can fully rehydrate.
Growing dahlias in pots
Many varieties of dahlia can be grown in pots all year round, providing a splash of colour on patios and balconies. Small to medium-sized dahlias, such as mignon and ruff dahlias, as well as slow-growing water lily, ball and pompom dahlias, do well in containers. Avoid growing cactus dahlias, which can grow to over 2m in height – as a general rule, only grow dahlias which don't usually require staking.
Grow potted dahlias in a warm, sunny and sheltered spot, protected from strong winds. Water regularly and feed with a phosphate-rich liquid fertiliser once a week.
Use free-draining, peat-free compost and plant the tubers about halfway down, so that the buds on the tuber shafts are only lightly covered with soil. Water well. Pinch out the shoots when they're around 10cm long, to encourage bushy growth.
Dahlias will come back every year, but if you live in a cold area, in winter you may need to move pots indoor. Simply move them to a frost-free spot, such as an unheated greenhouse. For dahlias growing in the ground, you will need to dig up tubers and store them under cover. Then, in spring, remove as much compost from above and around the tubers as you can, and replace with fresh compost. This will give the tubers a fresh burst of nutrients necessary for the best possible display.
Where to buy dahlias online:
- Crocus - Choose from a huge range of colours and shapes, and take advantage of discounted prices if you buy multiple collections of dahlia tubers
- Thompson & Morgan - Shop the new 2022 range of varieties, including ‘Electro Pink’, which is the world’s first dark leaved cactus dahlia, as well as the dwarf ‘Lubega Power Tropical Punch’ that’s ideal for containers
- de Jager - Established bulb specialists with an impressive collection of dahlia tubers, in a range of colours and flower shapes
- Dobies - Great selection on offer, with offers and discounts on specific collections
- Sarah Raven – great selection with lots of different varieties
You will need
- Dahlia tubers
- Large pots
- Peat-free multi-purpose compost
- Plant labels
- Pen
Total time: 30 minutes
Step 1
When planting dahlia tubers, ensure the joint where the roots meet the stem is facing upwards. Label your pots and grow on in a greenhouse or sunny windowsill. Keep the tubers well watered.
Step 2
Pinch out the tips of the main shoot, down to the top pair of leaves. You also need to remove most of the shoots growing from the tuber, except for five. This encourages bushy plants, strong, vigorous growth and a lot more flowers.
Step 3
When all risk of frost has passed, harden off your dahlias by placing them outside during the day and bringing them in at night. After a week they will be ready to plant out into their final growing positions.
Frequently asked questions
How do you take care of a dahlia plant?
To encourage lots of flowers, use a slow-release fertiliser for dahlias growing in pots and deadhead plants regularly to encourage more flowers to form. Stake tall varieties of dahlia and tie them in as they grow. Water dahlias in pots regularly during hot weather, keeping the compost moist.
Do dahlias grow better in pots or in the ground?
Dahlias grow well in pots and in the ground, but bear in mind that it is easier to move potted dahlias undercover over winter, than it is to lift tubers. If you live in an area that gets cold winters, it may be easier to grow dahlias in pots. It's better to grow large varieties in the ground, as this will provide more room for their roots.
How do you identify an eye on a dahlia tuber?
The eye is a small bump that can be found at the top of the tuber near the stem. The bump is sometimes purple or green.
Do you separate dahlia tubers before planting?
It's not necessary to separate dahlia tubers that you've just bought before planting. You may want to divide overgrown clumps in your garden, or that you have overwintered, before replanting in early spring. Divide the tubers at the neck, using a clean sharp knife. Make sure each section has one shoot or eye, and one set of roots.