By Teresa Conway published
If you're wondering how to grow dahlias, then you've come to the right place. After falling out of fashion for a while, these beautiful blooms have staged a big comeback and their newfound popularity shows no sign of waning. After all, these incredibly varied plants offer something for everyone.
Dahlias are totally versatile, too – you can plant them in borders, grow compact cultivars in containers, or treat them as a cutting-flower crop for show-stopping displays indoors. They can also be very good value for money – a single dahlia tuber can produce blooms from the end of June right through to the first frosts.
Whether you want to fill your flowerbed ideas or just test out one or two types, we've rounded up tons of top tips on how to grow dahlias below. And, once you've finished reading, our guide to garden borders might also come in handy for planning the rest of your planting scheme.
How to grow dahlias: step-by-step advice
Dahlias, which grow fresh from tubers every year, aren’t very good at pushing up through herbaceous plants. So, if you're growing them in a border, it's best to give them their own bit of space. However, there are also some that are perfect for growing in pots. These will look stunning lining a path or for your patio gardening ideas.
Garden expert Tamsin Hope Thomson for Amateur Gardening shares her top tips for how to grow dahlias:
- Pick a spot which gets plenty of sun (especially important if you want to leave the tubers in the ground over winter), with well-draining soil.
- If you're using a container, use a rich compost.
- Dig a square hole around 12 inches wide and deep, and space out your tubers about 24 inches apart.
- Then fill back up with compost. Keep the compost on the dry side until signs of growth appear, then water more frequently.
The most successful dahlias also have a good supply of well-rotted manure placed around the base soon after planting. Whether you've done this or not, the plants should also be fed every few weeks throughout the growing season. Alternate between a seaweed tonic and a potash-rich tomato feed.
If you're looking for more beautiful blooms to grow alongside your dahlias, then our guide on how to grow peonies is a good place to start.
When should you plant dahlias?
Dahlias are tender plants, so it's important to keep them protected from frosts. Because of this, it's generally best to start them off undercover in your greenhouse ideas in March or early April. Then, plant them out once the temperatures outdoors are reliably warmer – generally around May to early June.
Remember to harden them off before planting, by standing the pots outside in the garden for a week or so.
How to care for dahlias
The beauty of dahlias is that they're not overly demanding, so can be added to your plot as part of your low maintenance garden ideas. However, they do require the right care at the right time to keep them happy.
During the summer and early autumn months you will need to water them regularly throughout dry spells. Remember to feed them, too.
Don't be afraid to cut flowers off because this will actually help your dahlias. Regular picking encourages them to keep on producing flowers – what a win! Deadhead regularly and check for pests and signs of other disease.
How to stake dahlias
Some dahlias are taller than others, which means they'll need a little more support to stop them from toppling over. So, if you want to know how to grow dahlias, it's worth knowing these tips:
- Dahlias can be very brittle at their base, meaning whole stems are easily broken if it's windy.
- Ideally, plants should be staked at the time of planting in late spring to early summer.
- Use bamboo canes to support the plants and tie the stems with twine at 30cm intervals. If you haven't done this already, make sure you do so as soon as possible, as your dahlias get taller.
- Be careful not to damage the roots as you insert the canes, and make sure they are as close to the plant base as possible.
- Larger plants may need several stakes. Continue to tie in the stems as the plants grow taller for added support.
How to take cuttings from dahlias
Gardening expert Ruth Hayes of Amateur Gardening shares her step-by-step tips for taking cuttings from dahlias. It's a fantastic way to get new plants for free – ideal if you're after cheap garden ideas.
- Mix seed compost with perlite in a four inch clay pot, then add a little water to dampen it.
- Using a clean knife, remove just a few strong shoots from your dahlia plant, each at about four inches in length.
- Remove the lower leaves, otherwise they may rot when you pot your cuttings up.
- Dip the ends of your cuttings in rooting compound – this will help to promote strong and healthy root growth.
- Insert the cuttings into the compost and perlite mix and carefully firm them in.
- Seal the newly-potted cuttings in a plastic bag and place somewhere light and warm – such as in your greenhouse or on a sunny windowsill. New roots will soon begin to develop.
If you want to try this technique with other plants too, our guide on how to take cuttings from plants has tons more info.
What are the different types of dahlia available?
Dahlias are one of the best cottage garden plants and the choice available is huge.
To help narrow it down they are grouped into categories depending on flower type:
These are easily recognizable by their resemblance to pom poms. Their flower heads are perfect spheres that are made up of layers of petals that curl inwards.
This type, as you can imagine, are spiky – like a cactus. Their petals are narrow and curve slightly outward.
Single varieties are less dramatic but still beautiful. They have only one layer of petals that can be either slightly rounded or pointed.
These resemble underwater creatures. The inner petals are smaller and more clustered and get larger and flatter at the outer edges. They are sometimes called 'powder puff' dahlias.
This variety is named because it has two rings of petals, one larger on the outside and the smaller one which sits on the inside and resembles a collar.
They have shallow flower heads and look stunning in a cottage-style border. The petals can be curved, slightly curved or completely flat.
These dahlias have the largest blooms of all the varieties. Their double flower heads sport broad and slightly flat petals, often with a blunt end, with no central disc. The classic 'Cafe Au Lait' is a good example.
If you're looking for dahlias to use for cut flower arrangements, go for longer stemmed varieties. The more you cut, the more the plants produce!
How do you get bigger blooms on your dahlias?
To get good, long dahlia stems and larger (but fewer) flowers, cut off all side growths 60cm below the growing tip. This allows plenty of stem for cutting these if you want to arrange them in vases indoors. And, it also allows lower shoots to go on growing to produce replacement stems.
Another tip to ensure show-stopping blooms is to retain just the top bud and pinch out all the other flower buds immediately below.
What should you do with dahlias in winter?
If you want to know how to grow dahlias and have very cold winters, you'll want to lift the tubers and store them indoors. Tamsin Hope Thomson for Amateur Gardening explains how:
- Wait until the foliage has turned black from the frosts, then cut the plant down to about six inches.
- Lift the tubers and brush away the soil with your hands.
- Leave them to dry for a few weeks in a shed or indoors.
- Then store in a box of compost of sand over winter, before replanting the following spring.
If you're in a warmer part of the world then you don't have to lift the tubers. Instead, cut back the plants and then apply a layer of mulch or compost to the crowns for extra insulation.
Our guide to mulching has more info should you need it.
Problems to look out for with dahlias
As with most plants, a few pesky problems can arise. Here's a few to look out for:
- Dahlias can be prone to pests including snails and aphids, so check them regularly for signs of infestations. Pick off snails or catch them in beer traps. You can use chemicals to get rid of aphids, but a more environmentally-friendly option is to introduce natural predators such as ladybirds and hoverflies. Our guide on how to get rid of aphids is full of useful advice.
- Earwigs can also be a pest to watch out for when learning how to grow dahlias. You can collect them in simple paper traps. Crumple up newspaper and place in an upturned flower pot which can sit on top of your stakes. This attracts the earwigs and keeps them off the plants.
- Diseases such as powdery mildew can be a problem for dahlias. You can improve your chances of prevention by removing dead and damaged foliage before it starts rotting and by creating good airﬂow around plants.
Where to buy dahlias
In summer it's easy to get hold of potted up dahlias that are already in full growth. Alternatively, in spring, you can buy bagged up tubers from garden centers or online.
You can also pre-order tubers and rooted cuttings from specialist nurseries for an early spring delivery. However, make sure you've got a frost-free place like a greenhouse with heating or use insulating fleece when starting them off, depending on how cold it is.
Shop dahlias in the UK:
- Buy dahlias at Amazon
- Buy dahlias at Crocus
- Buy dahlias at Dobies
- Buy dahlias at Suttons
- Buy dahlias at Thompson & Morgan
- Buy dahlias at You Garden
Shop dahlias in the US:
- Buy dahlias at Home Depot
- Buy dahlias at Walmart
- Buy dahlias at Amazon
- Buy dahlias at Summer Dreams Farm
- Buy dahlias at Golden Rod Gardens
- Buy dahlias at Triple Wren Farms
Dahlias to try in your garden: 13 beautiful picks
We've rounded up some of our favorite dahlias so you can give them a go in your own garden.
1. 'Art Deco'
The compact 'Art Deco' dahlia is great if you're looking for small garden ideas, as it only grows to around 15 inches tall.
It's perfect for growing in containers and boasts warm orange-colored petals which gently twist to show off their pink undersides.
2. 'Cafe Au Lait'
Very on-trend at the moment, the stunning 'Cafe Au Lait' dahlia is popular for use in summer bridal bouquets.
The soft, creamy blooms can reach 25cm across so are real show-stoppers. They look equally spectacular in the border as they do in a vase. The plants grow to a height of around 50 inches (1.2m).
3. 'Karma Choc'
Originally bred for cut flowers, the long-lasting blooms of 'Karma Choc' have a vase life of up to 12 days. So, if you're after some of the best cutting garden flowers, these are a great contender.
In a deep plum red, the blooms are a romantic and dramatic addition to any garden. They grow to a height of around 35 inches (90cm).
4. 'Otto's Thrill'
'Otto's Thrill' is a beautiful dahlia with giant and decorative blooms. The elaborate rose-pink flowers span up to 25cm across, so it's definitely one to include if you want your borders to make a statement.
The pretty petals also have a slight wave to them, evoking a romantic feel. The plants grow up to 50 inches in height (around 120cm).
5. 'Bishop of Canterbury'
If you're after some of the best bee friendly plants, then the 'Bishop of Canterbury' dahlia is a classic.
A single-flower variety, it has vivid magenta-red flowers and makes a jolly addition to the border. These plants grow to a height of 35 inches (90cm).
6. 'HS Wink'
Part of the Happy Single series, 'HS Wink' dahlias sport bright pink flowers from July to September with deep-purple middles.
They're another compact type, growing only to about 30 inches tall and 16 inches wide. This makes them a good choice for pots, to pep up patio ideas.
7. 'Black Narcissus'
The 'Black Narcissus' dahlia is a double-bloomed, cactus kind. The deep wine plumes of spiky-looking petals create instant drama in a planting scheme – ideal for modern garden ideas.
These will flower from July to September. Growing to around 39 inches in height, they're another good choice for slightly smaller spaces.
Love the dramatic look of dark-colored flowers? You'll find more suggestions in our guide to the best black plants.
8. 'Crème de Cassis'
A prolific bloomer, 'Crème de Cassis' offers waterlily-type blooms with two-toned petals – pretty pale pink on the top and deep plum on the bottom. Each flower head will span to around four to six inches, making them an impressive addition to your garden design ideas.
The plants themselves grow up to 36 inches in height, and span 18 inches across.
9. 'Small World'
The demure yet prolific pompom blooms of 'Small World' offer an elegant, creamy white tone to the garden. These flower heads may be smaller than many other types of dahlia, but they are certainly exquisitely formed. Again, they are a big favorite for brides – it's easy to see why.
The plants will grow to a height of around 39 inches (24 inches across) and will flower all through the summer.
10. 'Alfred Grille'
The pretty pink flowers of 'Alfred Grille' burst from a striking yellow center, making these a real vision of delight. Try filling jam jars or vases with them to make your summer garden party ideas feel extra special.
In the right conditions, these plants are a strong and prolific grower, and will reach heights of around 39 inches. They'll also offer blooms right up into October in many cases.
11. 'Waltzing Matilda'
The slightly waved coral-pink and orange petals of 'Waltzing Matilda' are a beautiful sight, and are loved by pollinators, too.
Its semi-double blooms will appear from July right up until November if the conditions are right. It's another smaller variety, at around 28 inches tall and only 12 inches wide, but still packs a punch.
'Waltzing Matilda' makes a lovely addition to warm-hued planting palettes – our guide on garden color schemes has more advice.
12. 'Honka fragile'
As Tamsin Hope Thomson for Amateur Gardening says, this variety looks like one of those spinning windmills that captivate children on the beach. Its petals are a crisp white shade, edged with a striking scarlet, and are slightly in-rolled.
It's another long-bloomer, offering a beautiful display right up until November. Growing to around 31 inches tall, it's also another favorite for butterflies and bees. Speaking of which, if you'd like to learn how to grow a butterfly garden, then our dedicated guide has lots of simple tips.
13. 'David Howard'
This variety is a prime example of why learning how to grow dahlias is totally worthwhile. The double orange flowers are nothing short of spectacular, and make a striking contrast against purple-bronze foliage.
It's compact in size (around 30 inches tall), meaning that it will work well in garden planter ideas or even at the front of borders. 'David Howard' flowers from July to October and makes a stunning centerpiece for outdoor dining ideas when arranged in a vase.
Teresa was part of a team which launched Easy Gardens magazine two years ago and she continues to edit it today. She is also the Gardens Editor on Homes & Gardens, Country Homes & Interiors, Ideal Home and Style At Home, so she is lucky enough to see and write about gardening across all sizes, budgets and abilities. What she is most passionate about when it comes to gardening are the positive effects it has on our mental health to grow and care for plants. Keeping our patches alive with greenery is great for the environment too and help provide food and shelter for wildlife. Finally, she finds it to be such a wonderful opportunity to tap into her creative side and she loves the feeling that she is crafting a space which has a life of its own. Audrey Hepburn summed gardening up perfectly when she said - “To plant a garden is to believe in tomorrow”.
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