In Nunavut, dahlias, cannas and gladiolus have to come out of the ground every fall. Lift them one to two weeks after a frost blackens the foliage. At Rankin Inlet that puts the job roughly between mid-September and early October, later if the frost holds off. The coldest month there averages a daily minimum of -34.3 °C, so nothing tender survives the winter outdoors. The timing is tight, the storage is easy, and most losses come from lifting too early or checking too rarely.
Do you have to dig them up in Nunavut?
Yes, with no exceptions worth planning around. Natural Resources Canada’s Plant Hardiness Site, using 1991-2020 normals, puts Rankin Inlet in Canadian hardiness zone 0a. That is a Canadian zone, not a USDA zone, and the two do not convert. The Canadian system is built on seven climate variables, the USDA system on one, and NRCan itself notes there are no simple conversions between them. Its own example: Canadian zone 4a overlaps nine USDA zones, from 3a to 7a. So a number like 0a tells you the neighborhood is severe, not which American zone to borrow advice from.
The temperature figure is easier to read. Environment and Climate Change Canada’s 1981-2010 normals for the Rankin Inlet station give a mean daily minimum of -34.3 °C in the coldest month (that is -29.8 °F, for readers comparing with the Lower 48). Not a record low. The ordinary, expected cold of a normal January or February, day after day.
Dahlias, cannas and gladiolus come from warm climates, and their storage organs (tubers, rhizomes and corms) are packed with water. Once the soil around them freezes, ice forms inside the tissue, the cells rupture, and the whole thing turns to mush at thaw. A layer of mulch slows that process in places where the ground freezes shallowly and briefly. In a place where the ground freezes deeply and stays frozen for months, mulch only delays the inevitable. The decision to write down: lift every tuber, rhizome and corm each fall, and store them indoors.
One caveat on geography. Rankin Inlet is the only reference station behind these figures, and a territory this large is not one climate. Communities farther north run colder and see their first fall frost earlier, so they have less margin. Nothing in the numbers suggests a pocket where leaving these plants under mulch becomes a reasonable gamble, and I would treat dig-and-store as the plan across the whole territory.
This is a different situation from hardy spring bulbs, which are built to sit frozen. If you are weighing what can stay put, Which Spring Bulbs Survive Your Winter sorts that out, and Planting Spring Bulbs in Nunavut covers the ones that do not need lifting. The three plants here belong to the other camp: summer-flowering, tender, and a little more work.
When to lift them
Wait for the frost, then give the plants a week or two. That is the whole rule, and in a short northern season it is also the part people get wrong in both directions.
Reading the frost
Environment and Climate Change Canada’s 1981-2010 normals for the Rankin Inlet A station put the average first fall frost on September 13. Treat that as the middle of a window, not a safe date. In one year out of two the first frost lands later than the average, so a gardener who circles mid-September on the calendar will be wrong about half the time. (The normals also cover 1981-2010, an older period than the 1991-2020 normals used for most US figures, so the two are not a perfectly matched pair.) Communities farther north see the frost earlier than Rankin Inlet, and the lifting window moves earlier with it.
The signal to watch is not the date but the foliage. A frost that only nips the leaf edges is a warning. A frost that turns dahlia leaves and canna foliage dark and limp, and flattens gladiolus leaves, is the signal. Lift one to two weeks after that blackening frost. At Rankin Inlet, that works out to roughly mid-September into early October, and later in a late-frost year. Plan for lifting between mid-September and early October, counting one to two weeks from the frost that blackens the foliage. The shorter the season, the more it pays to have boxes, labels and a place to cure ready before the first cold night. The First and Last Frost Dates in Nunavut page gives the wider picture if your community sits well north of the station.
Why waiting pays off
It is tempting to lift early, especially when a forecast shows a cold snap. Resist it if you can. While the foliage is green, the plant is still sending energy down into the storage organ. The frost that kills the top growth is the plant’s cue to stop and seal itself up. The skin on a dahlia tuber toughens, canna rhizomes firm up, and a gladiolus corm finishes swelling. Lift too soon and you get thin-skinned, undersized, soft pieces that lose water quickly or start to rot in the box a few weeks later. The shortened season at this latitude means they are already running late, and an early lift makes them later still.
The flip side matters as well. If you leave them for weeks after the blackening frost, you risk the ground hardening to the point where a garden fork can no longer work it without slicing through tubers. Dahlia necks are brittle, and a stab through a clump costs you the piece. Lift while the soil is still workable.
Lifting without damage
Cut dahlia and canna stems back to a short stub, then push the fork in well out from the clump and lever upward, never yanking on the stem. Gladiolus corms lift more easily; loosen the soil beside the row and shake the plants free. If a cold snap is forecast before you are ready, a blanket or tarp over the bed overnight can buy a few days. Plants in pots are simpler: stop watering after the frost and carry the whole pot inside.
Storing them over winter
The goal is simple to state: keep them cool, dark and just damp enough that they neither rot nor shrivel. In practice that balance depends on which plant is in the box.
Cure first, then clean lightly
Straight out of the ground, everything carries surface moisture, and moisture sealed into a box is how rot starts. Spread the pieces out in a sheltered spot indoors, out of direct sun and away from heat, and let the skin dry until it feels dry to the touch. Brush off loose soil by hand. A light cleaning is enough; scrubbing and soaking can nick the skin and invite rot. Trim any broken or soft bits and keep those pieces separate from the good ones.
Location matters more in Nunavut than in most places. With coldest-month minimums averaging -34.3 °C at Rankin Inlet, an unheated shed, porch or entryway will freeze, and frozen storage organs are dead ones. Keep the boxes inside the heated envelope of the building, in a cool back room or closet, away from heaters and vents and out of the light.
Three plants, three needs
| Plant | What you store | Moisture | Packing |
|---|---|---|---|
| Dahlias | Tubers with a bit of crown | Barely damp | Boxed in a lightly moist, loose material such as peat moss or wood shavings |
| Cannas | Fleshy rhizomes | Slightly moister than dahlias; they dislike drying out completely | Boxed in lightly moist material, with some soil left clinging |
| Gladiolus | Corms (new corm separated from the old one) | Dry | Mesh or paper bag with good airflow, no damp packing |
Dahlias sit in the middle: enough moisture in the packing to keep the tubers plump, not enough to wet them. Cannas want a little more of it, because their rhizomes shrivel faster when the air is dry, and they should never be cured to a papery state. Gladiolus corms are the odd ones out. They want a longer, drier cure until the outer husk feels papery, and then they go into a bag where air moves around them. Pull off the shriveled old corm from the base, keep the plump new one, and the tiny cormels can be saved if you want to grow them on.
The monthly check
Storage is not a set-it-and-forget-it job. Look through every box once a month, from lifting until spring. You are looking for three things: soft or moldy pieces (pull them out immediately before they spread), wrinkled, light, rubbery pieces (add a few drops of water to the packing, or close the lid more tightly), and condensation inside a closed container (open it for a day to air out). Five minutes per box. It is the single step that saves the most plants, because both rot and shriveling are easy to stop when caught early and hard to reverse later.
What goes wrong
Most failures fall into four patterns, and each has a recognizable look.
Rot shows up as soft, dark, sour-smelling patches, sometimes with gray or white mold. It starts where the skin was cut or bruised, or where moisture sat in a sealed box. Prevention is dull but reliable: cure fully before packing, discard damaged pieces, use packing that is only barely damp, and give the box some air. When you find rot during a monthly check, cut it out cleanly, let the cut dry, and keep that piece apart from the rest.
Shriveling is the opposite problem. Tubers turn wrinkled, light and leathery, and badly dried ones never recover. It happens in rooms that are too warm or dry, or in packing that was left bone dry. Cannas show it first. The fix is a little moisture in the packing and a cooler spot, found early enough to matter. Gladiolus corms are the exception, since they store dry by design and a slight wrinkling in the husk is normal.
Lifting too early produces both of those problems at once. Thin-skinned, immature pieces lose water fast and rot easily, and it is hard to tell the cause by midwinter. The prevention is patience: wait for the frost that blackens the foliage, then give it the week or two.
The fourth is geographic: leaving them in the ground on the strength of advice written for milder places. A guide that says cannas or dahlias overwinter under mulch in some zone is describing ground that freezes shallowly, and Canadian zone 0a at Rankin Inlet is not that place. Even if you were tempted to translate zone numbers across the border, NRCan warns against it. Dig them up, every year, and look at the Spring Bulbs section for the plants that really can stay put.
Common questions
Can I leave dahlias in their pots and just bring the pots inside?
Yes, and in a short season it is the easiest route. Stop watering once frost blackens the foliage, cut the stems back, and move the whole pot to a cool, dark spot inside the heated part of the building. Keep the soil barely damp, not wet. Check the pot monthly, the same as you would a box of loose tubers.
What if the first frost has not come by early October?
The September 13 figure is a mean from the Rankin Inlet A station, so half of all years run later. Keep waiting while the soil is still workable, since the plants are still maturing. But if a hard freeze is about to lock up the ground, cut the foliage back and lift anyway. Slightly immature tubers that you can store and watch are better than ones frozen in the soil.
Do tulips and daffodils need the same treatment?
No. Hardy spring bulbs are built to sit through a frozen winter and generally stay in the ground. The lifting routine applies to the tender summer bloomers. You can compare the two groups in Spring Bulbs, and Which Spring Bulbs Survive Your Winter sorts out which spring bulbs can handle your conditions.
Does the Rankin Inlet date apply to my community?
Only as a starting point. The frost average comes from one station and from 1981-2010 normals, an older period than the 1991-2020 figures used for the US, and colder communities farther north see frost earlier and should lift earlier. Watch your own foliage and your own forecast rather than the calendar, and browse the other Nunavut guides for local timing.