How to Store Dahlia Tubers Over Winter

Dahlias are tender, so their tubers must be lifted before hard frost and kept frost-free and barely damp. Get the storage conditions right and they come back strongly.

Quick answer

Lift after the first frost, dry, and store frost-free and barely damp

When to lift: After the first frost blackens the foliage, before hard frost.
Preparation: Cut stems to about 10 cm, lift, and let the tubers dry.
Storage medium: Barely damp compost, vermiculite or newspaper in a box.
Conditions: Frost-free and cool — roughly 5–10°C — and check monthly.

Why lift at all?

Dahlias are tender: their tubers survive only where the ground stays above freezing. In cold or wet winters, left in the ground they either freeze or rot, especially in heavy soil. Lifting them and storing them somewhere frost-free turns a single plant into one you can grow again next year — and, once divided, into several.

When to lift

Timing matters. Leave the plants as long as you can so the tubers mature and store better, but do not let them meet hard frost.

After the first light frost blackens the leaves, cut the stems down — the plant is finished for the year.
Before hard frost, when the ground itself begins to freeze, dig the tubers up.
If you garden in a mild area, some growers leave dahlias in the ground under a deep mulch; that is a judgement call, not a guarantee.

Lifting and preparing

Cut the stems back to about 10 cm above the tuber to make a handle and reduce rot.
Dig wide — well outside the clump — to avoid spearing the tubers.
Lift the whole clump and shake off as much soil as will come away.
Dry it. Turn the clump upside-down for a couple of weeks somewhere airy and frost-free so water drains from the hollow stems.
Remove loose soil and any damaged or soft tubers before storing.

Do not wash the tubers unless they are very muddy; dry-cleaning them off is safer. Wet tubers rot in store.

Storing over winter

The aim is to keep them frost-free, dark and just moist enough to stop them shrivelling.

Pack in barely damp compost, vermiculite, wood shavings or newspaper in a box or crate. Damp, not wet.
Keep at roughly 5–10°C — a frost-free garage, shed or cool cupboard.
Label the box with the variety, since tubers look alike.
Check monthly. Remove any soft or mouldy tuber immediately so rot does not spread, and moisten the packing only if the tubers are starting to shrivel.

Rot spreads quickly

A single mouldy tuber can spoil the box. Check it over regularly and set aside anything that feels soft or smells.

Signs of trouble in store

Check the box about once a month and act early, because problems spread between tubers sharing a crate.

What you find	What it means	What to do
Soft, mushy tuber	Rot	Remove it at once; check the rest
White or grey mould	Too damp or too little airflow	Remove affected tubers, dry the box, ventilate
Shrivelled, wrinkled tubers	Too dry	Mist the packing lightly or add slightly damp material
Green shoots in midwinter	Too warm	Move somewhere cooler; pot up if growth is strong

Dividing the clump in spring

Stored clumps can be split before you plant them out, which turns one plant into several. Once shoots appear, cut the clump into pieces with a sharp knife, making sure each piece carries at least one healthy shoot and its own share of tuber. Dust the cut faces and pot each division up, or plant straight out once the danger of frost has passed. The same lifting-and-splitting method applies to other perennials in how to divide hostas and daylilies.

How many tubers to keep

A single large dahlia clump can hold many tubers, but the only ones that matter are those with an "eye" — a small growing point where a shoot will form. Blind tubers with no eye never grow, however healthy they look. Before storing, run a hand over the clump and keep it whole; division is easier in spring when the eyes swell. When you do split it, a piece with two or three tubers and at least one eye makes a strong plant, and the rest can be shared or composted.

Frequently asked questions

Can I leave dahlias in the ground over winter?

In mild, well-drained gardens, some gardeners do, under a thick mulch. In cold or wet ground the tubers usually rot or freeze, so lifting is the safer choice.

Should I wash the tubers before storing?

Better not to. Dry them off and knock off loose soil, but avoid soaking them, which invites rot.

When do I start them again in spring?

Pot them up indoors a few weeks before the last frost so they have shoots before they go outside. See the guide to dividing perennials for splitting the clump at that point.

Sources and research notes

Storage advice follows UK horticultural guidance for tender dahlias; exact temperatures are comfort ranges, not exact requirements.

Written and edited by the Seedledge Editorial. Every guide answers one real growing question, is checked against the sources listed above, and is updated when guidance changes. We are an independent editorial desk, not horticultural professionals — read how we research and update our guides.