The Ultimate Guide to Growing Dahlias

Everything You Need to Know About Growing Dahlias by Hannah Miller at DIY Gardening


Dahlias are tuberous perennials that vary in height but often grow up to 6ft.

Favoured for their large autumn blooms, which come in all colours except blue, they also make excellent cut flowers.

Dahlias aren’t maintenance-free but are fun to grow.

Here is an overview:

Planting Out

Dahlias are usually grown from tubers, and the tuber must have an “eye”; if it doesn’t, it won’t produce a stem.

The tubers, stems, leaves and flowers are sensitive to frost, so the tubers should only be planted out after all risk of frost has passed.

Alternatively, start them in pots in a sheltered spot such as a greenhouse, then plant out after the last frost.

The ideal spot for dahlias is in sunlight but sheltered from the wind. They also like a little space and won’t perform so well if placed in a crowded border.

Early Season Care

Slugs see dahlia leaves as an “all you can eat buffet” and will sliver past other plants just to feast on the dahlia. This pest can cause damage throughout the year, but spring and early summer is when damage is most severe, usually when the leaves are more tender.

Dahlias can grow tall and leggy with few stems and a small number of blooms. To encourage the plant to grow bushy with more blooms, one should pinch out the main stems when the plant has about three or four sets of buds on the stem.

Dahlias are hungry and thirsty plants, so they should be watered frequently and given regular fertiliser.

As dahlias are top-heavy plants, some supports, frames or stakes will be required.

Late Season Care

Dahlias bloom from late summer into autumn and usually up until the first frosts.

By selectively pinching off buds, the gardener can control the size of the remaining flowers.

Stems typically produce flowers in sets of three, with each flower moderate in size. By removing one or two of the buds, the gardener can force the plant to send energy into the remaining flower, which will grow much bigger, the largest dahlia bloom in the world is over 14 inches!

Late season care usually involves tying the stems to frames and stakes, selectively removing buds, watering the soil and feeding with a low-nitrogen fertiliser so the tender stems don’t grow too leggy.

Explore the links at the top of the page where you’ll find everything you need to know about growing dahlias.

This guide to growing dahlias was created by the team here at DIY Gardening

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