How to grow dahlias from tubers

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.

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's 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.