How to Dig, Divide and Store Dahlia Tubers

The first hard frost of the season turns a dahlia patch from a wall of colour into blackened stems overnight. It's a bittersweet moment — the end of a long flowering season — but it also marks the start of the last big job of the year: getting your tubers out of the ground, divided, and safely into storage for spring.

This is the highest-value task in the whole dahlia calendar. Every clump you dig can become five, ten, even twenty new plants for next season — but every division that's handled carelessly is a bed space lost for a whole year. Here's exactly how we do it at Pure Maiden Farm, from lifting the clump to tucking labelled divisions away for winter.

1. Digging (Lifting)

Dahlias are lifted in autumn, once the first hard frost has blackened the foliage — this is the plant's own signal that it has gone dormant and the tubers have finished bulking up underground.

1. Wait for a hard frost to blacken the plant before you lift anything. Don't rush this — the tubers are still bulking up right until dormancy sets in.

2. Clear the bed first. Remove all stakes, twine and drip irrigation before you start digging.

3. Cut the stems back to the ground.

4. Lift each clump with a pitchfork, not a shovel. This is a small technique change that makes a real difference — the tines let soil fall away from the clump, while a flat shovel blade tends to slice straight through tubers you wanted to keep.

5. Shake off the excess soil by hand.

6. Place clumps into deep, ventilated crates. Don't wash them yet if you're planning to divide within the next few days — a light coating of soil actually helps stop the tubers shrivelling while they wait.

7. Store the crates in a cool dark room at 5–10°C (40–50°F) until you have time to sit down and divide properly. This isn't a job to rush through in the field.

Why the pitchfork matters: lifting is unavoidably slow, physical work, but one simple tool swap — fork instead of shovel — meaningfully cuts tuber damage without costing you any extra time.

2. Dividing

This is the step that takes the most care, and the one new growers need the most practice at. A division is only viable if it keeps an intact eye and an intact neck — get this step wrong and you can lose an entire clump's worth of next season's plants.

What is "the eye"? The eye is the small, swollen growing node found on the neck of the clump, close to where the old stem was cut off. This is the only place next season's shoot will grow from. A tuber without a visible, undamaged eye and neck — no matter how big and healthy it looks — will simply never sprout.

Standard Work

1. Rinse the clump thoroughly with a hard spray of water from the hose to wash off all the soil. If you have sandy loamy soil, you can skip this step.

2. Let it drip dry. Wet clumps are harder to divide accurately, and a wet tuber makes your blade more likely to slip.

3. Gather your tools: sharp secateurs, a heavy-duty pair of loppers, and good lighting. Don't try to do this job in dim shed light.

4. Split the large clump roughly in half first, using the loppers or secateurs. This gives you smaller, more workable pieces before you start hunting for individual eyes.

5. Work from the halved clump, cutting individual tubers away one at a time. Check every single cut for a visible eye and an unbroken neck before you commit to it.

6. If you have plenty of a variety, it's fine to leave two or three tubers joined together rather than forcing a division down to a single tuber. A slightly bigger division gives the neck more strength and the plant a faster start in spring.

7. If the neck breaks, discard the tuber immediately. It's tempting to try and save it, but a broken-neck tuber will almost always rot in storage instead of sprouting — don't waste storage space or hope on it.

8. Dust the fresh cut surfaces with fungicide powder before the divisions go into storage.

9. Label every division by variety before it leaves the work area. Mixed-up stock is the kind of mistake that doesn't get caught until the wrong colour flowers next summer.

Be ruthless on the front end. Discarding a doubtful tuber the moment you spot the problem is far cheaper than the storage space — and the bed space next spring — wasted on a tuber that was never going to sprout.

3. Storing and Pre-Sprouting

1. Store labelled divisions in a cool, dark room at 5–10°C (40–50°F), in ventilated crates. On a smaller scale, layering tubers between damp media like potting mix, wood shaving, vermiculite in a lined bin works well — a little vermiculite in the base, a layer of tubers, more vermiculite, and repeat until the bin is full. Individually wrapping tubers (plastic wrap works fine) is another option if you're only storing a handful.

2. Check crates periodically over winter. Shrivelled tubers mean the storage area is too dry — mist them lightly. Soft or mouldy tubers mean it's too wet — improve airflow, and remove any affected tuber immediately before rot spreads to its neighbours.

3. In early spring, pre-sprout divisions in trays of damp propagating mix for 2–3 weeks before you plant them out in the field.

4. Only plant divisions that show visible new growth from the eye. Anything that hasn't broken dormancy by planting time should be left out of the bed — it's a far cheaper check to make in a tray than to discover a gap in the row weeks later.

Getting your first dahlia stock established is a genuine investment of time and money — but once you have a healthy base, every tuber you plant can produce five to twenty more by the end of a single season. Divide and store well, and by spring you'll have far more tubers than you started with, ready to fill next year's beds (and probably enough spares to share).

For everything on the other end of the cycle — bed prep, planting depth, pinching and season-long care — see our companion guide: How to Plant Dahlias