Storing Canna Rhizomes: Digging, Drying and Winter Storage
The short answer
Storing canna rhizomes lets cold climate gardeners save these tropical plants for next year. Extension guides say to let frost kill the tops, cut stems back, dig clumps with a fork, dry them briefly and store them cool and dry. Iowa State suggests 40 to 50 degrees Fahrenheit. Check them through winter for rot or shriveling.
When should you dig canna rhizomes?
Cannas are tender in cold winters. NC State Extension says cannas are native to tropical Africa and Central and South America and will sustain injury if left in the ground below 25 degrees Fahrenheit. It advises gardeners in zones 6a and 6b to cut plants to the ground right after the first frost and lift the rhizome clumps.
Timing matters. University of Wisconsin Extension says to let frost kill the tops but not to let clumps face a hard freeze, which turns the stem to mush. It notes that once frost kills the foliage, you should dig within a few days so rot organisms do not enter through damaged top growth. Iowa State University Extension says to dig a few days after a hard killing frost. Purdue Extension says to let frost killed tops dry for several days first. Pair the job with your fall garden cleanup after cannabis harvest.
How do you dry canna rhizomes?
Dig with care. Wisconsin says a digging fork is less likely than a shovel to cause injury, and that pathogens readily enter injured areas and cause rot in storage. Loosen the soil several inches back from the plant on all sides before lifting.
Cannas need only brief drying. Iowa State says to leave a little soil on the clumps and let them dry for several hours. Purdue says to turn the clump over and dry it for a few hours. Wisconsin says to dry the roots for a day or two, out of direct sun in a dry, ventilated area at 60 to 70 degrees Fahrenheit.
How should canna rhizomes be stored?
| Step | Why | Notes |
|---|---|---|
| Cut tops to 4 to 6 inches | Makes clumps easy to handle | Iowa State figure |
| Dig with a fork | Avoids wounds that rot | Wisconsin advice |
| Dry a few hours to two days | Firms the surface | Out of direct sun |
| Pack in a dry medium | Holds steady moisture | Peat or vermiculite |
| Store at 40 to 50 °F | Holds dormancy | Never let clumps freeze |
Sources: Iowa State University Extension, University of Wisconsin Extension, NC State Extension, Purdue Extension.
Iowa State says to place cannas in big boxes, wire crates or mesh bags. Purdue says to set clumps on shelves or racks or hang them in mesh bags so air moves freely, and to store them where the temperature won’t go over 50 degrees Fahrenheit. NC State suggests a dry medium such as peat or vermiculite in a spot that doesn’t fall below 40 degrees. Wisconsin says cleaned roots can be wrapped in newspaper or layered in peat moss. Store them in paper bags or cardboard boxes at 45 to 50 degrees. It warns against airtight containers, since they build moisture and promote decay. Label each bag with the cultivar name.
How to: step by step
- Wait until frost kills the tops, but dig before a hard freeze.
- Cut stems back to 4 to 6 inches.
- Loosen soil all around, then lift clumps with a fork.
- Dry the clumps for a few hours to two days out of direct sun.
- Pack them in peat, vermiculite or newspaper in a box or paper bag.
- Store at 40 to 50 degrees Fahrenheit and check them through winter.
- Replant after the last spring frost, 4 to 6 inches deep.
Troubleshooting
Soft, rotting rhizomes: storage is too moist or clumps were bruised. Wisconsin says to remove rotting pieces. Air dry very moist bulbs for a few days before repacking in dry material.
Shrunken or wrinkled rhizomes: storage is too dry. Wisconsin says to moisten the packing a little with a spray bottle and repack.
Mushy stems at digging: a hard freeze hit first. Dig sooner next year.
Clumps freezing: the spot is too cold. Move them somewhere that stays above 40 degrees. Store your tools well too, see cleaning and storing garden tools for winter.
Ready for spring planting
Cannas come back reliably when dug on time, dried briefly and stored cool and dry. Divide in spring, then feed the bed with ideas from fertilizer and compost for growing outdoors on the Kind Seed Co blog.
Sources
- How do I overwinter cannas indoors?, Iowa State University Extension and Outreach
- Winter storage of geranium, canna, gladiolus, caladium and begonia (HO 85), Purdue Extension
- Storing tender bulbs for winter, University of Wisconsin Extension Horticulture
- Canna, NC State Extension Gardener Plant Toolbox
FAQ
Do cannas need to be dug every year?
In cold areas, yes. NC State Extension says cannas will sustain injury if left in the ground below 25 degrees Fahrenheit and advises gardeners in zones 6a and 6b to lift the rhizome clumps after the first frost for winter storage.
How warm can stored cannas get?
Purdue Extension says to store cannas where the temperature will not go over 50 degrees Fahrenheit. Iowa State University Extension suggests a cool, dry spot at 40 to 50 degrees. NC State Extension says the spot should not fall below 40 degrees.
Should canna clumps be divided?
Wait until spring. University of Wisconsin Extension says to wait until spring to divide and to leave at least three eyes per division. Purdue Extension adds that each division needs a piece of old stem base, since new growth buds sit in the old stem.
When should stored cannas be replanted?
NC State Extension says to return the rhizomes to the ground in spring after the last frost. Plant them 4 to 6 inches deep and space them 12 inches to 3 feet apart, in rich, well drained soil with full sun to partial shade.
Can I store cannas in a sealed plastic tub?
University of Wisconsin Extension warns against airtight containers because they cause moisture buildup and promote decay. Use a ventilated cardboard box, paper bags, mesh bags or wire crates so air can move around the clumps through winter.
