How to plant out dahlias

BBC Gardeners' World Magazine

Published: Friday, 5 April 2019 at 12:18 pm

Learn how to plant out dahlias in our detailed guide, with tips on mulching and aftercare.

JanFebMarAprMayJunJulAugSepOctNovDecAt Its BestyesyesyesTo Doyes

Save

If you've overwintered your dahlias, May is the time to plant them out in the garden.

While you can plant dahlia tubers directly into the soil, it's good to give them a head start under glass, before hardening off and planting out in late May – learn how to pot up dahlia tubers in spring.

When you get to planting your dahlias in the ground, leave 15cm to 45cm between plants, depending on the ultimate size of your variety. Avoid planting dahlias in wet or shady sites, and dig the area over deeply before planting, incorporating lots of compost, to keep these hungry plants in top condition.

As for dahlia care, check out these expert tips on caring for dahlias.

Discover how to plant out dahlias, in this step-by-step guide.

You will need

Sturdy wooden stakes
Well-rotted manure
Garden twine
Secateurs

Total time: 30 minutes

Step 1

Hammering stakes into the soil

Before planting out your dahlias, hammer several 1.2m stakes into the soil. Make sure they are firmly placed and unlikely to wobble, as these will provide support for your dahlias.

Step 2

Digging a hole

Dig a hole at the base of each stake, about twice as wide as the dahlia rootball.

Step 3

Adding well-rotted manure to the planting hole

Add a deep layer of well-rotted manure, home-made compost or or peat-free multi-purpose compost to the bottom of the hole, to increase nutrients and aid moisture retention.

Step 4

Planting out the dahlia

Water each plant thoroughly before gently removing it from its pot. Tease out the roots, then settle the rootball into the hole.

Step 5

Filling compost around the planting hole

Plant each rootball deeply, so the top is 5-8cm below the soil surface. This will help to support the brittle stems.

Step 6

Watering the dahlias

Using your heel, firm the soil around the plant, then water well so it settles the soil and soaks down to the roots.

Step 7

Mulching around the dahlias

Spread a 5-7cm-deep layer of mulch over the soil around the plant. This should stop it drying out in summer.

Step 8

Weaving garden twine around the stakes

Weave garden twine back and forth between the stakes, running it at different heights to hold the stems.

Step 9

Cutting the tips of the dahlia stems

Once the plants are 30-50cm tall, cut out the tips of the main stems, to encourage side shoots to form.

Step 10

Water generously when the weather is dry, and add liquid fertiliser every two weeks. Cut flowers as required.

Cover tender new shoots with fleece on frosty nights, so they aren't damaged.

Secateurs

The perfect gift for gardeners

Gift 12 months of Gardeners’ World magazine, and Niwaki Sentei Secateurs, to a loved one. Enjoy year-round expert tips for a thriving garden.

Gift a subscription today

Great gardening savings - straight to your inbox

Sign up to the BBC Gardeners’ World offers newsletter for exclusive deals, seasonal savings, and early access to special promotions.