When to plant dahlias for fabulous flowers the size of dinner plates

They're one of the trendiest blooms to add to your garden, but you'll need to know when to plant dahlias if you want them to grace your home with spectacular colours all summer and autumn.

As is the case with any green-fingered task, it's not enough to know how to plant dahlia tubers – you need to know when to do it, too. And that's always the case, whether you're planning on growing them in pots or in your garden borders.

With that in mind, then, we've pooled our extensive garden knowledge to bring you a definitive guide on when to plant these oh-so-dramatic flowers.

When to plant dahlias 

'With a huge variety of sizes, from tiny little bursts to large flowers the size of dinner plates, in a glorious rainbow of colours from elegant whites, deep reds, a multitude of pinks and so much more, it’s no wonder that dahlias are so popular with gardeners,' says Charlotte McGrattan, Hardy Nursery Stock Buyer at Hillier Garden Centres.

'Dahlias have become the "in trend" flowering plant over recent years due to the rise of gardeners on social media showing how many stunning varieties there are available to grow,' agrees Morris Hankinson, director of Hopes Grove Nurseries. 

Morris Hankinson

Morris Hankinson is the founder and managing director of Hopes Grove Nurseries Ltd, the UK’s only specialist grower-retailer of hedging plants. He established the thriving business in 1992, shortly after graduating with a Commercial Horticulture Degree from Writtle College, Essex. 

'Dahlias have, in fact, been in Europe for over 200 years after originally being brought over from Mexico where they are native and grow as a perennial,' he adds.

It stands to reason, then, that the origins of the must-have dahlia will impact when to plant it.

'The important thing to remember when planting these pretty plants is that they will not tolerate cold soil, so you’re best to wait until any late cold snaps or frosts have passed,' says Charlotte.

'If you’re planting a tuber in a greenhouse, you can do so in March, but if you’re planting directly into the soil we’d recommend waiting until late spring,' she goes on  – although Monty Don’s top tip for growing dahlias involves 'forcing' your tubers in February.

'From April onwards you can plant tubers into gardens, for a wonderful riot of colour from summer right through to autumn,' adds Charlotte. 

Morris agrees, adding that this is why it's so important to learn how to overwinter dahlias.

'Any tubers that are left in the ground over winter without protection will most likely rot in the cold, wet, frosty conditions,' he says, ' so you need to know when to plant dahlias that you have lifted and stored over winter.'

FAQs

What is the best month to plant dahlias?

'If you have lifted dahlia tubers or bought new tubers these can be planted in pots at the end of March and kept undercover in a frost free place such as in a greenhouse, until they grow,' says Morris.

'Once they've been hardened off and all risk of frost has passed, they can then be planted out later in May onwards. If you are purchasing plants already potted, these can be planted out at the same time after all risk of frost has passed.'

Do dahlias grow better in pots or the ground?

It's good news for container gardenen ideas, as dahlias grow surprisingly well in pots. However, you need to be very careful to fertilise them well and to make sure they don't dry out: set up a watering schedule!

And just like that, you know exactly when to plant dahlias – so you'd best get to work quickly if you want your garden to be a riotous explosion of colourful flowers come summertime. 

Happy planting!