Want to know how to grow dahlias? After falling out of fashion for a while, dahlias have staged a big comeback in recent years and their newfound popularity shows no sign of waning. And we’re not in the least bit surprised, as these incredibly varied plants offer something for everyone.
They’re totally versatile – you can plant them in borders, grow compact cultivars in containers or treat them as a crop and harvest for beautiful cut flower displays. They can also be very good value for money – a single dahlia tuber will produce blooms from the end of June right through to the first frosts.
Read on for our top tips, then check out our guide to where to buy plants online so you can start stocking up with some of your favourite plants.
When to plant dahlias
Dahlias are frost-sensitive, so young plants cannot be set out until after the last frost. Harden off by standing them outside in the garden for a few days before planting. New tubers can be safely planted in pots from mid April, at a depth of 10cm. Keep the compost on the dry side until signs of growth appear, then water more frequently. Keep protected from frost, harden off in May and plant outside in early June. Add plenty of compost to the planting hole to give them a good start.
Different types of dahlias
The choice of dahlias available is huge – but to help narrow it down they are grouped into categories depending on flower type:
These are easily recognisable 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.
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 to grow dahlias
Dahlias, which grow fresh from tubers every year, aren’t very good at pushing up through herbaceous plants, so the easiest way to grow them is to give them their own bit of space. There are also some that are perfect for growing in pots which will look stunning lining a path or edging a patio.
Stake medium-to-tall dahlias using bamboo canes placed in a circle around the plant, and wrap with twine. Otherwise their beautiful big flower heads will cause them to topple over.
How to care for dahlias
The beauty of dahlias is that they're not overly demanding but they do require the right care at the right time to keep them happy. It's mostly during the summer and early autumn months that you will need to make sure you are watering them regularly during dry spells and feeding them with a high-potash fertiliser.
Don't be afraid to cut flowers off because this will actual help your dahlias! Regular picking helps them to keep on producing flowers – what a win! Deadhead regularly and check for pests and signs of other disease.
What to do with dahlias in winter
If you live in an area which gets very cold over winter you will need to lift your dahlia tubers as soon as the first frosts appear and store them indoors over winter. Cut back any excess stems to about 7cm and store them in a dry shed covered in dry compost to keep them warm. Plant them back outside in spring and gently pull the tubers apart to form new and healthy plants.
If you're in a warmer part of the world then simply apply a layer of mulch or compost for extra insulation! Head to our guide to mulching for all the info you need.
Problems to look out for with dahlias
Dahlias can be prone to pests including snails, earwigs and aphids, so check them regularly for signs of infestations. Pick off snails or catch them in beer traps.
Earwigs can be collected in simple paper traps. Crumple up newspaper and place in upturned flower pot which can sit on top of your stakes. This attracts the earwigs and keeps them off the plants.
You can use chemicals to get rid of Aphids but a more environmental option is to introduce natural predators such as ladybirds and hoverflies.
Diseases such as powdery mildew can be a problem for dahlias but you can improve your chances by removing dead and damaged foliage before it starts rotting and by creating good airﬂow around plants.
Beautiful dahlias to try in your garden
We've rounded up some of our favourite dahlias so you can give them a go in your own garden. Take your pick from these top choices.
DAHLIA 'ART DECO'
A container-friendly mini option boasting warm orange-coloured petals with a gentle twist that showcases their dark pink undersides. Height: 40cm.View Deal
DAHLIA 'CAFE AU LAIT'
Very on trend at the moment, and popular for use in summer bridal bouquets. The soft, creamy blooms can reach 25cm across – they look equally spectacular in the border and the vase. Height: 1.2m.View Deal
DAHLIA 'KARMA CHOC'
Originally bred for cut flowers the long-lasting blooms have a vase life of up to 12 days. In a deep plum red, they are a romantic and dramatic addition to any garden. Height: 90cm.View Deal
DAHLIA 'OTTO'S THRILL'
A giant and decorative bloom with elaborate rose-pink flowers up to 25cm across. The pretty petals have a slight wave to them. Height: 100-120cm.View Deal
DAHLIA 'BISHOP OF CANTERBURY'
A bee-friendly variety which has vivid magenta flowers and dark foliage, and belongs to the single-flower dahlia type. Height: 90cm.View Deal