How to store dahlia tubers over the winter

At the end of the growing season, exhibition dahlias should be removed from the ground and stored for the winter in a frost-free place. These tips will show you the proper way to lift and store your dahlias so the following spring they can be used for stem cuttings, or be divided and replanted.

How to store dahlia tubers over the winter

1. When to lift dahlia tubers

  1. Immediately after the first frosts in fall have blackened the foliage, cut the stems back to about 15 centimetres (six inches) above the ground. The roots can be left in the ground for two or three more weeks if light frosts come early in your area, but they should be lifted immediately if there happens to be a hard frost.
  2. With a fork loosen the soil around the tubers, being careful not to damage them, and lift them by pressing back on the handle.
  3. Using a blunt-ended stick, gently remove surplus soil from between the tubers.
  4. Take care not to break off any of the old stems.
  5. Tie labels to the stumps of the stems for easy identification.

2. Where to store dahlia tubers

  • Place the tubers upside down in a dry, airy place for about two weeks to allow the moisture to drain out of the stems.
  • If it collects there, it will cause the necks to rot, and although the tubers may not be damaged, the area of new growth will be lost.
  • The tubers must be completely dry before they are stored for the winter.
  • Dust the tubers with sulphur to prevent fungous attack, and store them in a cool, dry, frost-free place away from drafts.
  • Where winter temperatures stay above −9°C (16°F), a simple and easy way to store tubers is to place 15 centimetres (six inches) of dry leaves or peat moss in the bottom of a 60-centimetre-deep (25-inch-deep) cold frame.
  • Space out the tubers on the leaves, keeping them 20 centimetres (eight inches) from the sides of the frame.
  • Cover tubers with another layer of dry leaves or peat moss at least 30 centimetres (12 inches) deep.
  • Finally, cover with a piece of burlap or similar material to absorb condensation. The leaves will insulate the roots against heavy frosts.
  • Replace the frame top.
  • Alternatively, you can store the tubers in trays of dry sand or peat moss beneath the benches in a cool greenhouse or in a dry cellar or cupboard at 4° to 7°C (39° to 45°F).
  • Never store them in a warm cupboard, however; they will simply dry out and shrivel rapidly under such conditions.
  • When only a few tubers are to be stored, netting or sealing the roots will provide adequate protection.
  • For netting, first wrap the roots in straw.
  • Place tubers inside garden netting drawn tightly into a hammock shape; hang from the ceiling of a frost-free building until spring.
  • The tubers can also be placed in a box lined with one-centimetre-thick (half-inch-thick) sheets of Styrofoam (available at hardware stores and home centres).
  • Alternatively, store tubers by placing them in a heavy-grade, black plastic bag without additional packing material, and seal the bag tightly with wire. This will prevent the roots from dehydrating; however, there is a danger that they will sweat and rot.
  • You can also keep the tubers in a frost-free shed or indoors underneath the basement stairs if you have such a space.
  • In spring new shoots will have developed on the crowns.
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