When and How to Lift Dahlia Tubers for Winter

Lifting dahlia tubers correctly at the end of the season is the foundation of a healthy growing stock for the following year. Done well, you will carry most or all of your tubers through winter with minimal losses. Done carelessly, you risk the damage and rot that can wipe out a season's worth of accumulated tubers. The process is straightforward once you know what you are doing.

When to Lift — Reading the Signals

In most of the UK and Northern Europe, dahlias should be lifted after the first killing frost blackens the foliage — typically October to early November. The frost does two useful things: it kills the foliage and signals to the tubers that the growing season is over, and it begins the process of drying down the stems. You do not need to lift immediately after the first light frost — a few days' wait is fine — but do not leave tubers in the ground through a prolonged wet, cold period after a hard frost, as the risk of rot increases significantly.

The Lifting Process

Cut the stems down to approximately 15 cm above soil level. Insert a garden fork into the soil about 30 cm from the stem and work around all four sides of the plant, gradually loosening the soil before attempting to lift. Never lever directly under the crown — this risks snapping tuber necks and losing the eyes that are needed for next year's growth. Once the soil is sufficiently loose, place the fork under the root mass and lift gently, supporting the crown from below rather than pulling on the stem. Shake off the bulk of the soil by hand.

Labelling — Do Not Skip This Step

Label every clump as you lift it. In the excitement of lifting a large clump of tubers it is tempting to assume you will remember which variety is which — you will not, three months later when everything looks identical. Tie a weather-resistant label to the stem stub before you move the plant from its lifting position, recording the variety name and any notes (colour, height, performance this season). This information is invaluable when dividing and selecting tubers the following spring.

Draining and Initial Drying

Dahlia stems are hollow and fill with water during the growing season. After lifting, turn the clump upside down (crown downward, roots upward) and leave it in a frost-free, sheltered position — a greenhouse, shed, or porch — for 24–48 hours to allow water to drain from the hollow stems. This step significantly reduces the moisture content of the clump going into storage and is one of the most important factors in preventing rot. After draining, move the clump to a warm, well-ventilated area to continue drying for five to seven days before packing away.

Cleaning and Inspecting Tubers

Once the initial drying period is complete, remove any remaining loose soil from around the tubers — a stiff brush works well. Inspect each tuber individually for soft spots, discolouration, or mould. Cut away any damaged tissue with a clean knife and dust the cut surfaces with sulphur powder. Dispose of any tubers that are significantly rotted or clearly shrivelled and non-viable. Keep only firm, plump tubers with visible or potentially viable eyes near the crown neck.

Lifting Summary

• Lift after the first killing frost blackens the foliage — October to early November
• Cut stems to 15 cm before lifting
• Loosen soil all the way around before lifting — never lever through the crown
• Label every clump immediately on lifting
• Invert clumps for 24–48 hours to drain hollow stems
• Dry in a warm, ventilated space for 5–7 days before final storage