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Growing Dahlias: Summer’s Most Artful Flower

Showy and stunning, dahlias are a summer flower that deserves to be in every garden! Luckily, it is quite easy to grow dahlias from a tuber. Learn how to grow and care for dahlias so you can have a showstopping garden this summer.

How to grow Great Dahlias

With tens of thousands of varieties throughout the world, there is a dahlia flower in practically every size.

Large dinnerplate dahlia being held
Photo courtesy of Flowerbulbs.com

I’m talking tiny, bushy dahlias the size of a ping pong ball to full-sized flowers as big as soccer balls. They also come in every colour under the rainbow and there’s even a striking black variety floating around.

Small purple pompon dahlia
Photo courtesy of Flowerbulbs.com

Originally from Mexico, dahlias are a tropical flower that summers from August and well into the fall. Butterflies adore them, I adore them, and you likely adore them too. Let’s all grow dahlias so we can have the brightest coloured gardens on the block!

Photo credit: Thank you to Flowerbulbs.com for providing me with the gorgeous photos in this post and the descriptions of each type of dahlia.

I shared this video as part of the Random Gifts of Flowers project I am working on with them. The project and video were made in partnership with Flowerbulbs.com but this post is not sponsored.

Read more about Random Gifts of Flowers: Spreading Love Through Flowers and how to Plant Summer Flowering Bulbs for an Outstanding Display This Year.

orange dahlia flowers
Photo courtesy of Flowerbulbs.com

The 12 Types of Dahlias

With so many shapes, sizes, and colours to choose from, there are a ton of dahlia flowers out there. Here are some of the main dahlia plants you can expect to find.

Photo courtesy of Flowerbulbs.com
  1. Single-flowered: a single row of flat or cupped florets with a central disc. 12-24 inches tall.
  2. Anemone-flowered: a large outer ring of flat petals with a mass of tubular florets in the center. 24-36 inches tall.
  3. Collarette: a large outer layer of flat petals with an inner wreath of collar-like florets. 30-48 inches tall.
  4. Waterlily: full double blooms in a flattened shape. Up to 48 inches tall.
  5. Decorative: the Flowerbulbs.com 2021 summer bulb of the year! Learn more about this stunning bloom below.
  6. Ball: small globe-like variety with double blooms. Flat florets that are blunt or round-tipped. 48 inches tall.
  7. Pompon: another small, globe-like variety with double blooms. Florets are curled and blunt or round-tipped. 32-48 inches tall.
  8. Cactus: double flowers with long, pointed petals. 60 inches tall.
  9. Semi-Cactus: another double flower with long pointed petals, but the petals curl for half or less of their length. 60 inches tall.
  10. Peony-flowered: open-centered flower with 2 or more rows or rounded petals. 40 inches tall.
  11. Mignon: small variety with single layer of rounded florets 1-3 inches long. Well suited for containers. 20 inches tall.
  12. Topmix: another small variety of single-flowers. Quite bushy and well suited for containers. 14 inches tall.

    pink dahlias
    Photo courtesy of Flowerbulbs.com

Summer Bulb of the Year

The decorative dahlia has the honour of being called Flowerbulbs.com’s 2021 summer bulb of the year (even though it’s a tuber it’s categorized as a summer-flowering bulb). One of 12 groups of dahlias, the decorative dahlia is a popular variety due to its size and striking colours.

This plant has slender stems with oval leaves, and “ray flowers” that are wide, flat, and have round or pointed tips. They exist in short to tall varieties, ranging in height from 20 to 60 inches.

Since they have such long stems, they make for a wonderful cut flower perfect for tall vases. The bright burst of colour is sure to brighten any bouquet for Random Gifts of Flowers, and the cutting of the flower will encourage even more blooms on the dahlia plant.

dahlia flowers for a cutting garden
Photo courtesy of Flowerbulbs.com

How to Plant Dahlia Tubers

While dahlia seeds do exist, they are quite tedious and difficult to grow. Instead, most folks grow dahlias from tubers. Dahlias are not at all hard to grow but they can’t handle freezing temperatures in the winter. In colder climates, they are either treated as annuals or dug up and stored for the winter.

Only plant dahlias when you’re 100% sure the risk of frost has passed. In most areas, you can plant dahlias around mid-May. Get a head start by planting them in pots in a greenhouse or indoors.

Plant the tuber so that the tip of the old stem is pointed upwards. Place tubers no deeper than two inches underground. Cover the dahlia tuber with soil and lightly press down. After planting, thoroughly water the area.

Dahlias need sun, including at least a couple of hours of the morning sun. The tubers are planted just below the surface so that are warmed by the sun’s heat and begin growing ASAP.

Dahlia flowers work well as border plants due to their long flowering period. In full sun, they have strong stalks and act as a garden feature. The taller varieties can line the back border while shorter varieties can be planted in the beds or in the front border. Be sure to pay attention to the variety and height on the packets when planting because moving when they are blooming can cause them too much stress, making them flop and reducing blooms.

how to grow dahlia
Photo courtesy of Flowerbulbs.com

Dahlia Plant Care

Once you’ve planted your dahlia tubers, you can expect shoots to emerge a few weeks later. Give your shoots 4-6 more weeks (depending on the type of dahlia) and you will get your first flowers. Typically, this is the beginning of August.

If you pinch out the main stem approximately 3 weeks after planting, you will be rewarded with a bushier plant.

Water your dahlias if the weather has been fairly dry. In the event of heavy rain and wind, you may need a stake to support tall dahlia varieties.

Deadheading will be your key to more blooms. Dahlias will continuously bloom as long as you make an effort to remove any spent flowers.

grow dahlias at home
Photo courtesy of Flowerbulbs.com

Can You Leave Dahlias in the Ground in the Winter?

For many of us, unfortunately, the answer is no. Since they are a tropical plant, dahlias are only considered a perennial and winter hardy in US zones 8 or above.

For the rest of us, we can dig up our dahlia tubers before the first frost. Store tubers in a cool yet frost-free place for the winter. Come spring, you plant them again once the fear of frost has passed.

white dahlia flower
Photo courtesy of Flowerbulbs.com

Force Start Dahlia Flowers Indoors

A well-known tip is to force start summer bulbs indoors in order to get blooms earlier. Just like seed-starting, you can plant tubers indoors at the end of March to mid-April. Plant them in a pot the same way you would outside.

Once the risk of frost has passed, around mid-May, place your pot outdoors to get your dahlia plant used to the conditions. After a week, plant your dahlia in the ground.

This means you will have flowers a month earlier than if you planted the tubers directly in the ground. You can expect blooms beginning of July. Plus, you won’t have any snails who like to munch on the young, crunchy dahlia leaves.

Dahlia Winter Care and Storage

My gardening pal, Erin over at The Impatient Gardener, has a great video on how to pull dahlias out of winter storage and pot them for an early start. She is a bit of a dahlia addict (Sorry, Erin, it had to be said) so if you love dahlias, be sure to follow her on YouTube and Instagram.

Growing Dahlias in Pots

Dahlias make for a gorgeous container flower. If you don’t have a garden but instead have a balcony or patio, you can still grow these gorgeous flowers.

The key to growing dahlias in pots is choosing the right variety. Dwarf varieties work well in pots including Mignon, Topmix, Dahlietta, Dahlstar, Dahlinova, and Gallery dahlias. Alternatively, you can include tall dahlias as a centerpiece for larger containers.

If you plant dahlias in a container, choose a pot with drainage holes in the bottom and lower sides. Adding a layer of clay granules to the bottom of the pot also helps to increase aeration for the roots. Plant with good potting soil and then you’re good to go.

rounded dahlia flower
Photo courtesy of Flowerbulbs.com

If you can’t get enough of dahlia flowers, I highly recommend Floret Farm’s Discovering Dahlias by Erin Benzakein. It is a full guide all about growing and arranging dahlias and is a must-have book for any serious dahlia growers.

What type of dahlia is your favourite to grow? Let me know in the comments down below which dahlia you plan to plant using this guide.

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