When, Where and How to Plant Your First Dahlias

Written by Hannah Miller. Reviewed by horticulturist Elizabeth Smith. Published to Dahlias on the 5th November 2021. Updated 28th February 2023.

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Dahlias are my favourite garden plant, and I’m so glad to see more varieties on sale in garden centres after a slight lull in their popularity a few years back.

Dahlias aren’t the easiest plant to grow, but I’m confident that if you follow my 8 pointers below, you’ll fall in love with this stunning garden perennial.

If you’ve never grown a Dahlia before, this guide is for you, and I’ll cover:

  • The different types of dahlia.
  • What to look out for on the tuber.
  • How to store them until the weather is warm enough to plant them outside.
  • Starting them early; the why, how and when.
  • The best location.
  • Early season tips top get your Dahlias off to a head start.

Here’s just six photos out of the hundreds I took this summer:

Red and white dahlia
Orange dahlias
Purple dahlia flower emerging from a bud
Smaller dahlia blooms on stems
Large yellow and orange dahlia bloom
Dahlia bloom next to measuring tape

Dahlias have been grown in Europe for over 200 years, and there are over 50,000 varieties, but most can be grouped into about a dozen categories.

Here are the three of the most popular dahlias, I have experience growing each and I’ve seen these in countless gardens.

Decorative Dahlias (shown above) – These are the most popular, and they include my favourites; the famous “Dinnerplate” variety, which produces flowers up to a foot wide.

Pompon and Ball Dahlias – Most are slightly more compact, but I’ve grown some to over 10 inches. These blooms are ball-shaped and I’ve seen them perform well in architectural gardens as they add shape and interest to borders and even pots. The petals are concave and blunted at the tip.

Cactus Dahlias (shown above) – These have long pointed petals that roll back at the edges. In my garden they stand about against all other Dahlias. Semi-cactus varieties aren’t quite so pointy but are still striking.

The Gardening Chores website lists more varieties of Dahlias and photos for each, so check out their guide here.

Step 2: What To Look Out For

Dahlias grow from tubers that I can only best decsribe as thin, long potatoes.

These multiply under the soil and I usually lift them after the first frosts and them until the following spring where I split them into new tubers. However, I’ve found there is a caveat; the new tuber will only grow into a plant if it has an “eye” – a small dark spot near the neck of the tuber.

If the tuber doesn’t have an eye, it won’t produce a stem, and no plant will grow, so make sure any tubers you buy from your garden centre have an “eye”.

My dahlia tubers usually appear shrivelled and unhealthy if they’ve been out of the soil for any length of time, but I’ve found that this is perfectly normal, and most bounce back into life once they’ve been planted in the garden. 

Just make sure none are overly soft or squidgy as they’re probably rotten or diseased.

Step 3: How to Store Dahlia Tubers Until They’re Ready For Planting

I’ve been growing dahlias for over 10 years one thing they hate is frost.

Dahlia tubers should be stored in a sheltered spot until spring, and all risk of frost has passed.

Whether you’ve dug up your own tubers or purchased them online or from a garden centre, I’ve found the best way to store them is:

  • Get a cardboard box.
  • Fill it with an inch of compost.
  • Cut holes in the sides for ventilation.
  • Place the tubers inside, making sure they don’t touch each other.
  • Cover the tubers with compost.
  • Place the box in a shed, garage, porch cupboard or anywhere dark between 5° and 10°.

The tubers should be ready to plant out in the spring when all risk of frost has passed.

Dahlia tubers

Our dahlia tubers

Step 4: Start Them Off in Pots

Not everyone needs to start them off in pots and if you live in milder parts of the country, you can probably just plant them directly into the garden after all risk of frost has passed, but if you live in the north and have shorter summers, I’ve found that giving them a headstart will reap rewards later in the season.

First, check out this map as it will tell you the expected date for the last frost date for your area.

You can either wait until it’s safe to plant them in the garden or give them a headstart about 6 – 8 weeks before the last frost.

Here’s how I do it:

1) I place the tubers into pots and fill them with compost, I often use smaller pots and cram them into each one as they will only be in there for a month or two.

2) I then leave the pots in a greenhouse, a conservatory, porch or other area sheltered from the frosts and keep them watered but not waterlogged.

3) By the time the temperature warms up and there’s no risk of frost, I normally have Dahlias with at least a few inches of top growth, possibly much more, and they’re ready for me to transplant into the garden border or a large pot outside.

Step 5: How to Choose The Best Location For Your Dahlias

Through years of testing and experimenting, I’ve found the best location for Dahlias is:

  • In a bright spot with light on all sides if possible.
  • Near a water source, the gardener will need to water the dahlia several times a week and daily in heatwave conditions.
  • In a spot where the dahlia has some space, as they dislike crowded borders.
  • In a sheltered spot away from winds as the stems of Dahlias are very fragile.
  • In well-drained soil as the tubers may rot if left in waterlogged ground.

Step 6: Early Season Tips

Follow these tips to get your Dahlias off to a great headstart:

Have a Slug Plan – These pests love Dahlias, and in my garden, I’ve seen them nibble the dahlias all the way to the ground. You’ll need to plan ahead as in my garden, they quickly get through the foliage, as you see from the image below:

Slugs damage to dahlia leaves

Slug damage to a young Dahlia in my garden. If left unchecked they will devour all the leaves and weaken or kill the plant.

Try these slug repellants and traps.

Stakes and Supports – Dahlia stems are prone to snapping during the wind, so you’ll need to buy some stakes and ties or, even better, some frames to support the plant throughout the growing season.

The best garden stakes and Dahlia frames can be found here.

Feed and Fertiliser – We’ve already published a guide to the best fertiliser for Dahlias. In short, avoid nitrogen-rich feeds as Dahlias are often top-heavy, and I’ve seen nitrogen make the plant grow leggy.

Don’t Forget to Pinch Out – To encourage Dahlias to grow bushy rather than leggy, I found it best to pinch out the centre of the stems early in the season; the best time is when there are three sets of nodes on the stem.

Conclusion

Dahlias are beautiful late-summer perennials that produce plenty of often large and eye-catching blooms, but I’ve found they are tender and require more love and care than the average plant.

I hope this guide gets you off to a good start and you enjoy growing Dahlias as much as I do.

Meet The Author: Hannah Miller

Hannah is a former NHS administrator, mother of two and keen gardener with a horticulture qualification who loves growing new plants and experimenting in the garden.

She enjoys gardening as much as she cares about the environment and likes to share her knowledge with others.

This year is all about pollinators, and Hannah has set herself the goal of only buying new plants that attract pollinators; she aims to make the garden as bee and butterfly friendly as possible.

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Hannah Miller has been growing dahlias for many years, and the photos on this page were taken by her.

We also asked horticulturist Elizabeth Smith to review and fact-check this guide before publication.

Explore: Elizabeth Smith’s profile and qualifications.

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