Canna lilies are easy to grow, but they get particular about winter storage. Gardeners north of USDA Hardiness Zone 8 need to lift and store the rhizomes indoors each year, since cannas can’t survive a hard freeze in the ground.
The process is straightforward in theory, but rushing it can wipe out an entire season’s growth. I learned that firsthand. To be fair, I was dealing with a broken foot that disrupted my usual routine, but the result was the same: when spring arrived, nearly every rhizome had turned to black mush. Here’s how to overwinter canna lilies correctly, and what to avoid.
How to overwinter canna lilies
1. Dig after a frost, but before the ground freezes
Cannas, dahlias, gladiolus, and elephant ears all go dormant once temperatures drop below freezing. That’s when the rhizomes have finished storing energy for the following year, so it’s the right time to dig.
Waiting until after the first light frost lets the foliage die back naturally, which makes the job easier. However, don’t wait too long. Once the ground freezes, digging becomes difficult and cleaning the rhizomes is a chore. Aim to dig while the soil is still workable, using a shovel, spade, or garden fork.
2. Divide and inspect while you’re at it
You can trim the stalks before digging, leaving a 2- to 3-inch stub as a handle, though I prefer to lift everything first and cut back the stems with pruning shears afterward. Because canna rhizomes spread horizontally and produce new shoots quickly, dig at least 12 inches out from the stems to avoid damage.
Autumn is also the right time to divide large clumps into smaller sections. Each piece should have at least three visible “eyes” for strong spring growth. While dividing, inspect each rhizome carefully. Any dark or soft spots, or a foul smell, are signs of rot or disease. Discard those, and don’t store them with healthy rhizomes.
3. Cure them before storing
Curing is what prevents rot during storage. Spread the rhizomes out for about a week in a warm, dry, well-ventilated spot, such as a garage or basement, at around 70 to 80 degrees Fahrenheit. Brush off excess soil and make sure they’re fully dry before packing.
Some gardeners disinfect rhizomes with a diluted bleach solution, but I skip that step. Getting them clean and properly dried has always been enough.
4. Use the right containers and packing material
Once cured, lay the rhizomes in a single layer in a cardboard box so they don’t touch. Pack with peat moss, coconut coir, wood shavings, or a perlite-and-vermiculite mix. These materials hold moisture at the right level, dry enough to prevent rot but not so dry that the rhizomes shrivel.
Avoid plastic containers. They trap moisture and encourage mold. This is exactly where things went wrong for me. Unable to move easily with my broken foot, I stuffed the rhizomes into plastic trash bags, packed them tightly together, and left them in the crawl space. Total loss.
5. Store in the right spot and time the replant correctly
Canna rhizomes need cool, dark, and slightly humid conditions, ideally between 40 and 60 degrees Fahrenheit. Attics and unheated garages often run too cold. A basement, cellar, or heated garage is a better option.
In spring, once frost risk has passed and soil temperatures climb above 60 degrees, it’s time to replant. Check each rhizome for rot or pests before it goes back in the ground. If you want to speed up dormancy break, soak them in warm water for 12 to 24 hours first. Otherwise, plant directly with the eyes facing up.
What I’d do differently
Overwintering cannas isn’t difficult, but it does require some patience. The plastic bag mistake cost me a full season, and it was entirely avoidable. Cardboard boxes, proper airflow, and a consistent temperature are all it takes. If you’re storing for the first time, check on them once a month through winter and remove anything that’s starting to soften before it spreads to the rest.
For more plant care and gardening guides, browse Gabi’s List home and garden picks.