Dig and store canna bulbs after the first hard frost

Canna lilies, more commonly known as simply cannas, provide a lot of bang for the buck in any flower garden. Some varieties are grown for their flowers, others for their showy foliage.

The main disadvantage to them is they are tropical plants, so are not hardy in our area. That means if you would like to grow them in your garden next year, you will have to either buy more roots or dig and store them over winter.

The roots are often referred to as bulbs but they are in fact rhizomes, a type of root structure that grows underground and is the way the plants reproduce asexually. Virtually all canna varieties are grown from rhizomes.

Our cannas had a nice long growing season, but the first hard frost we had a couple of weeks ago brought that to an abrupt end.

At frost time a gardener has to make a decision: Do you dig and store them, or let them freeze and buy new ones next year?

Since I have such a hard time throwing out plants, I always dig as many as I can and try to find room for them somewhere. Or barring that, give away as many as possible. I know I’m not the only gardener who has the problem of too many canna roots. After all, that’s how I ended up with this latest batch of cannas. About three years ago another gardener gave me several roots and now I have barrels full of them.

It’s relatively easy to save them for planting next spring. Once the plants have been frozen by the frost (but not before) cut the stalks off about 6 inches from the ground. That gives you something to hold on to when digging and handling the roots.

There are very serious gardeners who insist that the stalks must be cut before the leaves thaw and turn brown from the frost. I was one of those intrepid gardeners who got up before dawn on a frosty fall morning and went out to cut my canna stalks. I did that every fall until one year I was not able to do it and found very little, if any, advantage to cutting the stalks like that. Still, there was something special about watching for frost alerts and anticipating an early morning trek to the garden.

A garden fork is the tool of choice for digging rhizomes. The distance between the tines makes it less likely you will hit and cut off a rhizome than by using the blade of a shovel. Also, less soil is dug up along with the roots. The process of digging and storing plant roots is called “lifting.”

Dig down with the fork about a hand’s width away from the stub of the stalk that you left trying to avoid hitting the roots. After one or two tries, you’ll have a good idea how close you can safely dig.

Leave most of the soil on the roots. Large clumps of soil may be carefully removed.

Set the dug roots in a garage or someplace away from freezing temperatures — the warmer the better — and let them dry for a few days. This drying period is preferable but because of time constraints I often pack up the roots right as I dig them from the garden.

I pack my roots in trash barrels with layers of damp straw alternating with a layer of roots until the barrel is full. In the past I’ve used peat moss or sawdust to pack my roots. Whatever is used must be ever so slightly damp and not wet. Some longtime gardeners swear they get better results by placing their roots upside down in the storage container.

You may leave the 6-inch stalk stub on the roots during storage. I usually trim them back to a couple of inches to save on storage space.

Storing cannas in packing material is not always used or necessary. Some gardeners place their cannas in a root cellar with just garden soil clinging to them. This works if the storage area has just the right combination of humidity and temperature. I’ve used that method in the past and have had success doing it that way.

Potted canna may be stored right in the container they were growing in.

It’s critical for storage temperature to be well above freezing all winter long; aim for not lower than 45 to 50 degrees. Colder temperature will chill the roots and cause decay to set in. Some gardeners will keep their roots as warm as 60 degrees. At higher temperatures the roots may dry out so will need to be checked more often.

When the roots are taken out of storage in the spring, the soil may be rinsed off and the roots cut into pieces if desired.

Cannas are usually planted directly into the garden once the soil warms up to around 60 to 65 degrees. If you want to get a head start on the season, you can take the roots out of storage and grow them in pots for a few weeks before planting them into the garden.

Even though the first filling frost in our area happened a couple of weeks ago, the soil still has enough residual warmth to protect canna roots from frosts for a while. So, if you haven't lifted yours yet, there is still time to do so. You can't wait too long though; eventually the ground will freeze and that will be the end of the cannas.

Here’s to more beautiful blooms next year!