Canna lilies are tropical perennials that produce beautiful blooms in a range of colors during the summer months. While cannas are not winter hardy in most climates, you can dig up the rhizomes (bulbs) in fall and store them over winter so you can replant them again in spring. Properly preparing your canna bulb bed for winter storage is important for ensuring the rhizomes survive the cold months and sprout new growth when replanted. This involves digging up the bulbs at the right time, cleaning and drying them, and then storing them in a cool yet frost-free spot until spring. With the right winter care, your canna lily bulbs can produce vibrant blooms year after year.
When to dig up canna rhizomes
Timing is important when digging up cannas for winter storage. You’ll want to dig up the rhizomes once the foliage and stems have been killed off by frost and the plants are completely dormant. This typically occurs after the first hard frost in fall. Digging up the rhizomes too early means they could potentially keep trying to grow. Waiting too long risks damage from freezing temperatures if the ground freezes over. The ideal window is generally late fall once the plants have experienced a killing frost but before the ground freezes.
Signs cannas are ready for digging
Here are some signs your cannas are ready to be dug up for winter storage:
– Foliage has turned yellow or brown after being damaged by frost
– Stems are limp and falling over
– Entire plant looks dried up and dead
– Hard frost has occurred and nighttime temperatures are consistently below 45°F (7°C)
– The ground is still thawed and not frozen over
Pay close attention to weather forecasts in your area to help determine when the first hard frost is expected. Once nighttime temperatures drop below freezing for an extended period, it’s time to dig up those canna rhizomes.
How to dig and store canna rhizomes
Follow these steps for properly digging up and storing your canna bulbs:
1. Cut back foliage
Once the foliage has been damaged by frost, cut off the dead foliage and stems to within a few inches of the ground. This removes top growth that is no longer necessary and makes digging easier.
2. Dig up rhizomes
Carefully dig around and under each canna plant to loosen the soil and access the whole rhizome clump. Lift the entire plant out of the ground. Knock off excess soil but be careful not to damage the rhizomes.
3. Allow to dry and cure
Lay the rhizome clumps out on newspaper or cardboard in a frost-free location out of direct sun. Allow them to dry and cure for 1-2 weeks. The drying and curing process help seal any cuts and prevent rotting during storage.
4. Clean rhizomes
Once cured, use a brush to clean off any remaining soil. Cut off any soft, mushy sections that may have rotted with a clean, sharp knife. Healthy rhizomes will be firm.
5. Divide clumps
Large rhizome clumps can be divided into smaller sections, ensuring each piece has at least 1-3 growth eyes or buds where new shoots emerge. Dividing helps stimulate growth next season.
6. Treat for disease prevention
Soak cleaned, dried rhizomes for 30 minutes in a fungicide/bacteria solution to prevent rot over winter. Or dust with a fungicide powder. Allow to dry again before storage.
7. Store in cool location
Place the dried, treated rhizomes in plastic bags, ventilated crates, or cardboard boxes filled with peat moss, vermiculite, or shredded paper. Store in a cool yet frost-free spot around 45-55°F. A basement, garage, or crawl space are ideal overwintering spots.
Preparing the bed for spring planting
Once you’ve dug up and properly stored your canna rhizomes for winter, the next step is preparing the garden bed so it’s ready for replanting in spring. Here are a few tips:
– Remove all plant debris
Clear away any remaining plant debris or dead foliage that was left behind when you dug up the cannas. Debris can harbor pests and disease over winter.
– Turn over soil
Turn over the soil using a shovel or garden fork to aerate and mix it. This eliminates any remaining clumps and works in any amendments to enrich the soil. Cannas prefer nutrient-rich, well-draining soil. Adding compost or manure in fall helps improve moisture retention and nutrients.
– Consider adding mulch
Spread 2-4 inches of shredded bark, leaves, straw or other organic mulch over the cleaned garden bed. The mulch insulates the soil, reduces weeds and keeps the soil evenly moist over winter. It can be pulled back in spring before replanting.
– Check drainage
Cannas don’t tolerate wet, soggy soil. Ensure the bed has adequate drainage by digging small trenches if needed to prevent water from pooling. Improving drainage prevents bulb rot over winter.
– Mulch around other plants
If you have any other non-hardy plants still in the bed like dahlias, mulch heavily around the base to protect the roots from freezing. The insulated soil retains some heat and increases their chance of survival.
When to replant canna rhizomes in spring
Once spring arrives, you can replant your overwintered canna rhizomes back in the garden after the last expected frost has passed and soil temperatures have warmed to at least 60°F. This is typically around 4-6 weeks before the average last spring frost date for your area.
Consistent soil temperatures in the mid 60s F indicate warm enough conditions for actively growing canna rhizomes. Planting too early in still cool soil causes slowed, stunted growth. Waiting until soil has sufficiently warmed avoids this issue.
Monitor soil temperature at planting depth (about 4 inches) with a thermometer probe. Refer to your local frost date averages. When soil and air temperatures align with historic frost-free dates, it’s safe to replant the cannas.
How to replant canna rhizomes in spring
Follow proper planting techniques in spring for strong, healthy canna growth:
– Soak rhizomes first
Soak the dried rhizomes in room temperature water overnight before planting. This rehydrates them and stimulates growth.
– Prepare garden bed
Work compost or fertilizer into the soil. Dig holes for each rhizome clump, spacing 2-3 feet apart. Holes should be at least 6 inches deep and wide.
– Plant at proper depth
Place rhizomes horizontally in the holes 4 inches deep, growth buds facing up. Cover lightly with soil, water thoroughly after planting.
– Provide support
Insert stakes next to cannas as they grow tall. Tie stems loosely to stakes to keep plants upright but not restrict them.
– Water and fertilize
Water frequently after planting while roots establish. Fertilize every 4-6 weeks to fuel growth. Apply mulch around plants to retain moisture and reduce weeds.
Ongoing canna care
Once your cannas are happily growing again in spring, a little regular care keeps them looking their best:
– Water and fertilize regularly
Provide consistent moisture and monthly feeding with a balanced fertilizer. Drought stress causes leaf scorching and stunted blooms.
– Stake and tie tall stems
Add taller stakes and loosely tie stems as needed to keep them vertical and prevent damage in wind/storms.
– Remove spent flowers
Deadhead faded blooms back to a leaf node to encourage more flowering. Prune off damaged foliage as needed.
– Watch for pests
Check regularly for common canna pests like aphids, spider mites, Japanese beetles. Treat promptly to avoid spread.
– Prep for winter dormancy
Cut back foliage and stems after frost. Dig and divide rhizomes for winter storage once they go dormant.
With proper care both before and after winter dormancy, canna lily rhizomes can provide striking, tropical appeal in gardens year after year. Pay close attention to timing when digging and replanting the bulbs. Provide ideal storage conditions over winter and resume care promptly each spring. Prep the bed well in fall and spring to optimize growth. A bit of diligence in overwintering will allow you to enjoy a healthy stand of gorgeous canna lilies every summer.