How To Plant Out Dahlias

How to plant out dahlias

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

A table displaying which months are best to sow, plant and harvest.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
At its best
At its best

Plant is not at its best in January

Plant is not at its best in February

Plant is not at its best in March

Plant is not at its best in April

Plant is not at its best in May

Plant is not at its best in June

Plant is at its best in July

Plant is at its best in August

Plant is at its best in September

Plant is not at its best in October

Plant is not at its best in November

Plant is not at its best in December

To do
To do

Do not To do in January

Do not To do in February

Do not To do in March

Do not To do in April

Do To do in May

Do not To do in June

Do not To do in July

Do not To do in August

Do not To do in September

Do not To do in October

Do not To do in November

Do not To do in December

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.

More on growing dahlias:

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.

 Avoid planting dahlias in wet or shady sites, and dig the area over deeply before planting.
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You Will Need

  • Sturdy wooden stakes
  • Well-rotted manure
  • Garden twine
  • Secateurs

Total time:

Step 1

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.

Hammering stakes into the soil
Hammering stakes into the soil

Step 2

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

Digging a hole
Digging a hole

Step 3

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.

Adding well-rotted manure to the planting hole
Adding well-rotted manure to the planting hole

Step 4

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

Planting out the dahlia
Planting out the dahlia

Step 5

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

Filling compost around the planting hole
Filling compost around the planting hole

Step 6

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

Watering the dahlias
Watering the dahlias

Step 7

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

Mulching around the dahlias
Mulching around the dahlias

Step 8

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

Weaving garden twine around the stakes
Weaving garden twine around the stakes

Step 9

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

Cutting the tips of the dahlia stems
Cutting the tips of the dahlia stems

Step 10

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

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

Secateurs