When Should I Plant Dahlias Outdoors?

Whether you’re growing them from tubers, seeds, or cuttings, planting dahlias in spring ensures a bright and bountiful display in summer.

Even better: they can stay in bloom until early frosts, though they’ll need protection from icy winters if you live in an especially cold area.

You can plant potted dahlias under cover or indoors from March to April.

But to plant them in the garden, you’ll generally want to get them in the ground from May to early June. However, that’s more down to a set of conditions associated with that period than the dates themselves.

Dahlias don’t do well at all in frost. Make sure the weather’s been consistently above 5°C in your area before planting them outdoors and that there’s absolutely no frost predicted, if you can.

And while the bright, sunny days we’ve seen recently might tempt you to get your gardening gloves on, remember this can be very changeable.

Still, the Royal Horticultural Society (RHS) said, sometimes, you can get away with putting stored tubers in the ground as early as mid to late April.

That’s because, while we might still get some frosts, the soil itself won’t freeze. So the tuber’s roots will be able to grow, and the shoots, which won’t come up for months, will only appear once the risk of frost has disappeared.

BBC Gardener’s World said we should get rid of all but five shoots from dahlia tubers before planting them. Though it might feel a bit brutal, “it will encourage bushy plants that will produce lots of flowers”.

Plant them about 60cm apart when you put them in the ground, and support new growth for all varieties, except dwarf kinds, with stakes.

They grow fast, so secure new growth every two weeks or so.

While they’re not especially fussy about soil so long as it’s relatively moist and well-drained, they do need to be placed in a sheltered, sunny spot to thrive.