Digging & Storing Tender Bulbs Through Alberta Winter

Timing

Wait for the first hard frost that blackens the foliage. Don’t dig before then — the plant is still moving energy from leaves to tubers, and digging early reduces next year’s vigour. After frost, you have 1–2 weeks before the ground freezes hard enough to make digging difficult. In Edmonton this is usually mid- to late September; later further south.

If a hard frost hasn’t hit by mid-October, dig anyway — tubers will keep going indefinitely if left, but you can’t dig frozen ground.

Digging

• Cut foliage to 10–15 cm above ground.
• Dig wide — start a spade-width away from the stem and work in. Tubers spread further than you expect, and a sliced tuber rots.
• Lift the whole clump gently. Don’t pull on the stem — tubers detach from the central stem easily.
• Brush off (don’t wash) loose soil. Wet tubers rot in storage.
• Label by variety with a permanent marker on the stem stub or a tag tied through the clump. You will not remember in March.

Curing

Set tubers in a single layer somewhere cool (10–15°C) and well-ventilated for 1–2 weeks. The skins toughen, surface moisture evaporates, and small wounds dry over. A garage, basement, or covered porch works. Don’t cure in direct sun (drying too fast cracks tubers) or warm rooms (sprouts the buds prematurely).

Storage

After curing, pack tubers in slightly damp (not wet) peat moss, vermiculite, sawdust, or coarse sand. Use a cardboard box, mesh bag, or paper grocery bag — never sealed plastic, which traps moisture. Tubers should be surrounded by medium, not touching each other directly.

Store at 5–10°C. Most basements and unheated garages stay in this range over Alberta winters; an old root cellar is ideal. Avoid spots that swing above 12°C (sprouts) or below freezing (kills).

Species notes

• Dahlias: Most demanding. Divide clumps now or in spring — each piece needs at least one “eye” (growth point) at the crown plus one tuber. Dust cuts with garden sulfur to prevent rot.
• Cannas: Hardiest of the tender bulbs. Cut foliage, lift entire root mass, store in barely-damp medium. Forgiving of slightly dry storage.
• Gladioli: Cure differently — warm and dry (15–20°C) for 2–3 weeks until the old corm under the new one breaks off easily. Then store the fresh corms cool. Discard the old shrivelled bottom corm.
• Tuberous begonias: Store dry in a paper bag at 5–10°C. Don’t use peat moss — they prefer drier storage than dahlias.

Monthly check-ins

Once a month through winter, look through the storage box. Compost any tuber that’s gone soft, mouldy, or shrivelled to a husk — rot spreads fast through a packed box. Mist the medium lightly if everything looks dry and shrivelled; the medium should feel just barely cool-damp, not wet.

By March, eyes will start to swell on dahlias — that’s your cue to wake the tubers up by potting them indoors for an early start, or to wait a few more weeks before planting back out after last frost.