Cannas are tropical and subtropical flowering plants that are grown for their large, colorful blooms. While cannas are perennials in warm climates, in colder regions they must be dug up and stored indoors over winter. Properly storing canna bulbs is crucial for their survival and successful winter storage allows gardeners to regrow cannas year after year.
Cannas form large underground rhizomes or bulbs that store energy and allow the plants to resprout each year. The key factors for successful winter storage of canna bulbs are proper timing, careful digging and handling, proper curing and drying, and storage conditions that prevent rotting, shrivelling and premature sprouting. By following some simple best practices, northern gardeners can successfully overwinter cannas bulbs for many years of enjoyment.
When to dig up canna bulbs?
Canna bulbs should be dug up after the foliage has been killed by frost but before the ground freezes. This generally occurs 4-6 weeks after the first frost. The foliage must be allowed to die back naturally to provide nourishment to the underground rhizomes. But digging must be completed before the ground freezes solid, which makes removal difficult to impossible without damage.
Ideally, lift canna rhizomes on a dry, mild day when the soil is moderately moist but not wet. Digging in very wet, muddy conditions can lead to injury. Try to dig at least 2 weeks before the first expected freeze or hard frost in your area so bulbs have time to dry and cure properly before storing.
How to dig and handle canna bulbs?
Use a garden fork or shovel to carefully loosen the soil and lift the rhizomes. Take care when digging to avoid puncturing, breaking or bruising the rhizomes. Damaged rhizomes are more prone to rotting during curing and storage.
Gently shake or brush off loose soil but do not wash the bulbs as excess moisture encourages rot. Washing also removes the papery outer shells that protect the rhizomes from drying out.
Handle cannas carefully to avoid nicks, cracks and other damage. Be very gentle when separating clusters of bulbs so as not to break the fragile fleshy rhizomes. Any broken or damaged portions should be dusted with a fungicide powder to prevent rotting.
Cut off and discard any very soft, mushy, diseased or rotting bulbs or sections of rhizomes. Healthy canna rhizomes are firm with visible growth nodes or eyes where new shoots will emerge.
Curing and drying canna bulbs
Freshly dug canna bulbs must be cured and dried properly before storage. This hardening off process toughens the bulbs, allows minor wounds to heal and removes excess surface moisture that could cause rotting.
Spread out the bulbs in a single layer on newspaper, cardboard, window screen or other breathable material. Provide good air circulation around the bulbs while protecting from direct sun. Cure bulbs at temperatures of 60-80°F for 1-2 weeks.
Canna bulbs are sufficiently cured when the skin is dry and papery. The rhizomes will feel firmer as excess moisture evaporates. When fully cured, store promptly to prevent shriveling.
Storing canna bulbs indoors
There are a few options for storing cured canna bulbs over the winter:
Pack bulbs in peat moss, vermiculite or shredded newspaper in boxes or ventilated plastic bags. Keep in a cool (40-50°F), dark place like a basement, garage or unheated room.
Bury bulbs in buckets filled with vermiculite, shredded leaves or bark mixed with peat moss. Store in a cool spot around 45°F.
Layer bulbs with dry peat, sand or vermiculite in plastic tubs or wooden crates. Place in a cool, dark location.
The ideal storage temperature for canna bulbs is 40-50°F. Warmer conditions can stimulate premature sprouting. Temperatures below 40°F may damage bulbs. Ensure bulbs do not freeze.
Store bulbs in a dark place to prevent growth. Check regularly over winter for any signs of rotting, shriveling, sprouting or pest damage. Discard any compromised bulbs immediately to prevent issues spreading.
Planting stored canna bulbs
When spring arrives, canna bulbs can be planted back outdoors once all danger of frost has passed:
In mid to late spring after soils have warmed above 60°F, plant canna rhizomes 2-4 inches deep and 12-18 inches apart in a sunny, well drained garden spot.
Water thoroughly after planting and provide consistent moisture until plants are growing strongly. Fertilize with a balanced fertilizer once new growth emerges.
Remove any sprouts that form while bulbs are still indoors. Wait to see where sprouts and growth nodes form after planting outdoors before removing any foliage. This allows the plants to properly emerge and establish.
With proper winter storage, cannas will quickly resume growth. You may get blooms the first year after overwintering bulbs. Mature plants grow rapidly and provide a tropical flair to gardens.
Storing canna bulbs in pots
An alternative to digging and storing bare canna rhizomes is to overwinter the bulbs right in their pots. This avoids any damage to the delicate bulbs that can occur during digging and replanting each year.
When overwintering potted cannas:
Before frost, cut back canna stems and foliage to 6 inches. Move pots to an unheated garage, shed or similar area that stays between 40-50°F over winter.
Water sparingly, just enough to keep bulbs from completely drying out. Aim for the soil to remain slightly moist but not wet.
In spring, move pots back outside once danger of frost has passed. Cut back any remaining foliage and provide water and fertilizer to stimulate new growth.
The bulbs may sprout earlier when overwintered in pots. Just remove any shrivelled foliage or stems that die back to allow new sprouts to emerge in spring.
Overwintering cannas indoors
In very cold winter climates, gardeners can overwinter cannas indoors as houseplants. When overwintering as houseplants:
Dig up bulbs after frost as usual and cure for 1-2 weeks in a frost-free location.
Pot up individual rhizomes or clusters of 2-3 bulbs in pots with drainage holes, using a well-drained potting mix. Bury bulbs 2-3 inches below the soil surface.
Water sparingly at first, keeping the potting mix barely moist until plants are actively growing.
Place pots in the brightest window available. Provide at least 4-6 hours of direct sunlight if possible.
Grow cannas at normal indoor room temperatures around 65-75°F. Avoid hot rooms or heat sources that may prematurely wake bulbs.
Fertilize monthly with a diluted houseplant fertilizer once plants are actively growing. Keep soil evenly moist but not wet.
In spring, acclimate plants to outdoor conditions before moving outside permanently after danger of frost. Gradually introduce to longer hours of sun.
Common problems overwintering canna bulbs
With proper handling, curing, drying and storage, canna bulbs can be successfully maintained from one growing season to the next. However, bulbs may suffer damage or fail to survive winter for various reasons:
Rotting from excess moisture is the most common issue. Ensure bulbs are dried properly before storage and kept just barely moist (never wet) while stored. Discard any soft or mushy bulbs showing signs of rot immediately.
Too dry conditions can cause bulbs to shrivel and desiccate over winter. Check stored bulbs occasionally and provide a little moisture if needed to plump them up.
Rodents like mice may chew on bulbs if they are not stored safely out of reach. Use rodent-proof containers and areas for storage.
Bulbs that sprout while in storage deplete their energy reserves. Remove sprouts until ready to replant. Maintain an ideal storage temperature around 45°F.
Inadequate curing or nicks/bruises to bulbs can allow decay organisms to invade and cause rotting. Handle bulbs gently and cure properly after digging. Disinfect any cut surfaces.
Insufficient soil moisture after replanting may inhibit sprouting. Ensure newly planted bulbs receive regular watering until up and growing.
Tips for success overwintering canna bulbs
Follow these tips to safely store your canna collection and enjoy their return year after year:
– Allow foliage to die back fully before digging bulbs
– Handle bulbs gently to avoid damage during cleaning and dividing
– Cure bulbs properly in warm, dry conditions for 1-2 weeks
– Select well-drained storage medium like peat or vermiculite
– Check stored bulbs periodically; discard any rotting bulbs immediately
– Keep stored bulbs moist but never wet; aim for 40-50°F temperatures
– Remove any sprouts that form on bulbs while in storage
– Repot in fresh, well-drained soil mix when replanting in spring
– Gradually acclimate potted bulbs before placing outside permanently
Conclusion
While cannas are tender perennials that cannot survive freezing winters, gardeners in colder climates can still enjoy their bold tropical flair. Carefully lifting the underground rhizomes in fall and properly storing them over winter enables regrowth year after year. With attention to harvesting, curing, and storage method, canna bulbs can be successfully maintained indoors and replanted once danger of frost has passed. By providing suitable winter care, northern gardeners can reliably grow cannas as if they were hardy perennials.
