Growing your own Dahlias

Dahlias are currently having a moment amongst gardeners and flower fans alike, and it’s not hard to see why.

They come in a range of shades, shapes and sizes, are easy to grow, and produce an absolute abundance of blooms for you to enjoy in the garden or bring into the home.

Originating in Mexico, dahlias are a sun-loving, late summer flower, typically blooming from July until the first hard frosts in the Autumn.

Sourcing your Dahlias

You can grow dahlias from seed, tuber, rooted cutting or as potted plants.

Growing from seed represents good value for money, but dahlias grown from seed won’t come ‘true’ to their mother plant, so it gives you very little control over their colour and form. If you would like to grow from seed, ‘Bishop’s Children’ will give you a bright and bold array of single flowers.

I tend to buy my dahlias as tubers or rooted cuttings, which gives you control over the variety and the potential for super healthy floriferous plants. I’ve personally found rooted cuttings to be the best performers in my garden, bought from Northern nursery Halls of Heddon.

Tubers are the most widely available - Sarah Raven, Farmer Gracy, Rose Cottage Plants, Withypitts Dahlias and Riverside Bulbs all carry a lovely range of varieties. You can also often pick up well priced tubers in garden centres and supermarkets.

It’s worth checking where your tubers have come from - those imported from the Netherlands and elsewhere bring a greater risk of plant virus such as gall. Sourcing British grown tubers and cuttings are a great choice to lower that risk.

How to grow dahlias

If you order your tubers or cuttings online, they are likely to arrive in March or April. The tubers can look pretty odd (like a little bunch of dried out sausages) - don’t worry, that’s normal!

It isn’t recommended that you plant your tubers or cuttings straight out into the garden at that point, as dahlias are not frost hardy and could be killed by a late frost or snow. The best thing to do is pop them in a 2 or 3 litre pot half full of fresh compost with the central stalk pointing straight up, then top up with more compost to cover the tuber and the bottom of the stalk.

Dampen your compost, but make sure it’s not too wet - dahlia tubers can rot in damp conditions. You shouldn’t water your tuber again until green shoots have sprouted - this can take a few weeks. Keep your pots indoors or in a greenhouse/coldframe to protect them.

It’s a good idea to ‘pinch out’ your dahlias when they have 3-4 pairs of leaves on the shoot, by snipping off the top set to just above the next pair with clean scissors (you can google this for a video!). This will delay flowering by a week or so, but will stimulate the plant to produce more flowers in the long run.

After the risk of frost has passed (usually around May in London) you can plant your dahlias out in the garden - make sure you choose a spot in full sun as they won’t tolerate shade. Well-draining soil is also important to avoid issues with tuber rot.

Spacing recommendations for dahlias vary - often around 70cm is suggested by suppliers but I’ve found 45cm is fine if you’re trying to save space. Removing the bottom leaves once the plant is fairly tall and established in the ground can improve air flow and lower the risk of powdery mildew.

You can also grow your dahlias in a large pot - make sure you choose smaller bushier varieties, which tend to grow to a height of 60-90cm rather than the 1m+ of most varieties.

Whether in the ground or a pot, it’s worth staking your dahlias unless it’s a very sheltered spot. The easiest way to do this is to pop a thick stake in as you plant out each dahlia, and tie them in as they grow.

If you don’t have anywhere to keep your dahlias under cover until May, you might want to buy them as potted plants instead. You can also buy ‘garden-ready’ rooted cuttings from Halls of Heddon which arrive in early June ready to be planted - I’ve found them to be great quality.

Overwintering dahlias

Dahlias will usually flower until the first hard frost, although they will slow and start to look less healthy as the days get colder and darker.

Even if you grew your dahlia from seed or cutting, by the end of its first season it will have produced a tuber.

The general wisdom is that here in the UK, tubers should be dug up after the first frost, cleaned off, and stored in sawdust (or similar) in a dry place over winter. This is to protect them from frost-damage and rotting during the cold and rainy winter months.

My personal experience is that it usually doesn’t get cold or wet enough in London for this to be necessary - over the last couple of years I’ve left my dahlias in the ground, cut back and covered with a thick layer of mulch (eg compost or strulch), and they’ve all come back in Spring. If a hard frost is predicted I might cover them with a layer of fleece for the night for extra protection.

So you can decide whether you want to lift or leave your tubers, or maybe do a bit of both as an experiment!

My favourite varieties

There are hundreds, if not thousands, of dahlia varieties to choose from, so you’ll find something for every colour scheme. Dahlias are grouped into different types depending on their shape and size, ranging from enormous and impressive ‘dinnerplate’ varieties to sweet ‘miniature ball’ types.

When choosing varieties, it’s lovely to have a mix of different shapes within a tonal colour palette, or an array of different colours if you like things bold. This works perfectly with one of my favourite ways to display dahlias - as single stems in bud vases on a mantlepiece or table setting.

If you want to make bouquets with your dahlias, the smaller, rounder varieties such as pompon, ball and small decorative can be easier to work with.

Single flowered dahlias tend to drop their petals most quickly when cut, but they are most beloved by bees and butterflies so well worth a place in your garden.

Here are some suggestions for dahlias I love in a range of colours and forms - see below for some pictures.

Dinnerplates: Cafe Au Lait, Penhill Watermelon, Thomas Edison, Labyrinth

Decorative: Sweet Natalie, Peaches, American Dawn, Senior’s Hope

Pompon and ball: Hamari Rose, Gypsy Night, Nuland Josephine, Burlesca, Jowie Winnie, Linda’s Baby, Wizard of Oz

Single/anemone/collarette: April Heather, Night Butterfly, Waltzing Matilda

Best for pots: Daisy Duke, Creme de Cassis, Happy Single Princess, Bacardi