← The Notebook
Notebook · Guide 8 October 2026 · seasonal

Waking dahlia tubers in spring (and getting free plants from cuttings)

Pot stored dahlia tubers up under cover in early spring, barely damp, then plant out after the last frost, usually late May. The first shoots make easy, free cuttings.

seasonalsave your money

Your dahlia tubers have spent the winter in a box in the shed, and now they look like a bundle of dry, wrinkled sausages. The good news: they're almost certainly fine. Pot them up under cover in spring, keep them only just damp, and they'll wake up. Start them early and warm, and the first shoots give you free plants as cuttings. The one mistake that ruins it is overwatering before the shoots appear.

01At a glance

  • When: spring, under cover. For cuttings or dividing, start earlier and warmer, in late winter to early spring.
  • How: top of the tuber just below the compost surface, frost-free, good light, compost only slightly moist.
  • The big risk: rot. The RHS warns that overwatering can quickly rot tubers that are slow to sprout.
  • Plant out: once there's no danger of frost, usually late May, or early to mid-June in colder areas.
  • Free plants: basal cuttings from the new shoots, or divide the clump once shoots show.

02Potting up stored tubers

  1. Check each tuber for rot. Cut away or discard any part that is soft and mushy.
  2. Find the right way up. The RHS describes them as a cluster of sausages joined at the top by the old stem. The old stem goes uppermost.
  3. Pot up in peat-free multipurpose compost, with the top of the tuber just below the surface.
  4. Keep them frost-free and in good light, in a greenhouse, porch or bright windowsill.
  5. Keep the compost only slightly moist. Water lightly and sparingly once leafy shoots appear. Some tubers are slow, so don't keep watering one that hasn't moved.

No greenhouse or windowsill? The RHS says you can plant dormant tubers straight into the ground in mid to late April. Shoots typically appear by early June. You'll get flowers later than with pot-started plants.

See our dahlia profile for the rest of the year, from staking to lifting.

03Free plants from basal cuttings

This is the best bargain in the dahlia year. Each new shoot that comes from the tuber can become a new plant, true to its parent.

  1. Start the tubers early and warm. The RHS suggests late winter to early spring, in a heated propagator or on a warm windowsill.
  2. Wait for sturdy shoots. The RHS's general guidance for basal cuttings is shoots 7–10cm high, with the leaves just unfolding.
  3. Cut as close to the base as possible, taking a sliver of the firmer tissue where the shoot joins the tuber. Use a clean, sharp knife.
  4. Strip the lower leaves and pinch out the soft tip.
  5. Insert into peat-free cuttings compost and keep it moist.
  6. Give them warmth and humidity. The RHS suggests bottom heat of 18–24°C in a closed propagator, or a clear plastic bag in a warm spot, aired at least twice a week.
  7. Expect roots in about 2–4 weeks. Then pot on into slightly larger pots as they grow.

04Dividing a clump

If you'd rather split the tubers than take cuttings, the RHS method is simple.

  1. Start the clump into growth in early spring in a shallow tray of peat-free compost.
  2. When the shoots are about 2.5cm tall, lift the clump and cut it into pieces.
  3. Every piece needs both roots and a shoot. As the RHS puts it, as long as there's a green bud at the top of each piece, it will make a plant.
  4. Pot each piece up and grow on somewhere bright and frost-free until late May or early June.

05Planting out without losing them

  • Wait for the frost to pass. The RHS says usually late May, or early to mid-June in colder regions. Dahlias are frost-tender.
  • Harden them off first, moving them outside by day for a while before planting.
  • Protect against slugs and snails. Young shoots are especially vulnerable. The RHS advice is to plant out sturdy pot-grown plants rather than tiny ones, use cloches where you can, and go out with a torch on mild, damp evenings to pick them off.
  • Pinch out the tip when the main stem is about 40cm tall for a bushier plant with more flowers.

06Mistakes that cost you plants

  • Watering a tuber that hasn't sprouted. The commonest way to lose one.
  • Planting the tuber upside down. The old stem goes at the top.
  • Dividing with no bud on the piece. It'll sit there and never grow.
  • Planting out in early May and losing it to a late frost.
Save your money
Don't buy new tubers before you've checked the old ones. Pot them up and give them time; slow ones often sprout later than you'd expect.
Take cuttings instead of buying more plants. One tuber can give you several new dahlias for the cost of some compost.
Skip copper tape and eggshells for slugs. An RHS study found no reduction in slug damage from copper tape, bark mulch, eggshells, sharp grit or wool pellets. A torch and an evening walk work better.

Dahlia sap can irritate skin, so wear gloves when taking cuttings or dividing. Before handling or planting where children or pets can reach, check the safety flags on our dahlia profile.

How we checked this

Every care and safety claim on this page is verified against horticultural and veterinary sources.

Sources: RHS — How to grow dahlias · RHS — Softwood cuttings · RHS — Slugs and snails

Checked 8 October 2026. If our advice ever conflicts with the RHS, believe them and tell us.