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Canna overwinter: When to dig up the rhizomes of the tropical plant and how to store them properly in the winter?

Canna plants are one of the easiest tropical plants for the gardener to overwinter – which is especially handy since they are also one of the most versatile plants for the summer garden. With their large, often colorful leaves and unusual, ever-blooming flowers in bright, cheerful colors, they give garden beds and containers a lush, exotic look. The plants also feel at home in water features on a semi-shaded patio. How to overwinter canna, learn from our article!

How to overwinter canna

Autumn and frosty temperatures signal that it's time to dig up the rhizomes

To overwinter canna, you do not need a greenhouse. The thick, fleshy rhizomes can easily be stored in a cool basement, garage or cellar in complete darkness – without heat lamps, timers or expensive lighting systems. So if you’ve worked hard to grow a beautiful collection of tropical cannas this season and hate to see them die through a cold winter, follow these simple steps to keep them blooming and reproducing in your garden for many years to come.

When should you dig up the rhizomes?

While cannas send tropical leaves skyward during the growing season, they also spread in the soil, forming shallow-rooted clumps of thick but brittle rhizomes. Fall and frosty temperatures signal that it’s time to dig up the rhizomes for overwintering. Wait until frost has visibly blackened the plant’s foliage before digging – usually in mid to late fall. The trick is to get the plants out of the ground before temperatures drop sharply and the ground freezes.

How to dig up canna lilies for overwintering.

Overwintering canna - separate the rhizomes with your hands

Use a digging fork to carefully pry the clump out of the ground. Since canna lilies root shallowly, this is easier than you think! If you are overwintering canna in pots, you can either store the plants along with the pot or remove the clump from the pot and proceed as you would with garden-grown plants, depending on how much space you have. Plants grown in pots need to be planted in fresh soil the next season for best results.

Separate the rhizomes with your hands. Proceed gently, but don’t worry if they break. The fleshy roots will dry out during storage.  If the rhizomes have been stored in garden soil, do not wash them as this will cause disease problems during storage. Instead, remove the soil and brush them lightly. However, if they were in a swampy area or pool of water (cannas are great pond plants!), it is advisable to remove the dirt and debris from a long season.

If the rhizomes have been stored in garden soil, do not wash them

Using a clean knife, cut off the old leaf stalks 1-2 inches above the rhizome. Then carefully inspect the rhizomes for rot or animal damage and discard those with signs of disease. If it is a large rhizome, you can use a clean knife to cut off rotten or damaged areas down to the clean, white flesh. Remember that different canna varieties look the same bare. If you dig up several varieties at once, place them in large, labeled cups (even if it’s just a piece of paper to go with them).

Properly store the rhizomes in winter

To overwinter canna, you do not need a greenhouse

Now comes the easiest part of all – the preparation of plants for storage. Traditionally, they are stored in containers or bags filled with slightly moistened peat moss or wood chips. However, if you are short on time or do not have any of these materials available, you can overwinter cannas by simply placing the sorted rhizomes in heavy-duty trash bags. The trash bags will help maintain a good moisture level without adding additional moisture. However you store the rhizomes, be sure to carefully label the bags or pots.

Recommended storage locations for overwintering.

When to dig up the rhizomes of the tropical plant and how to store them properly in the winter.

Find a cool, dark place that stays above freezing but below 13 degrees Celsius throughout the winter. Non-fluctuating temperatures are best as they prevent early sprouting. Some recommended storage locations are:

Crawl space
Unfinished basements
Unheated garages
Deep cold frames

Avoid outbuildings (barns, greenhouses, etc.) as temperatures often drop below freezing in the depths of winter.

When to plant flowers back in the garden

When can you plant the flowers again in the garden

As temperatures rise and spring returns, recheck your rhizomes – discard any that are rotten or diseased, and if some begin to sprout in storage, lightly moisten them with water to replenish resources. Cannas are tropical warm season plants. Not only will they be damaged if you plant them too early in the garden, but they will not grow vigorously until temperatures are warmer.

Natural timing for canna rhizomes.
Keep your storage areas cool, and once there is no danger of frost, plant the rhizomes outdoors or in containers in nutrient-rich soil with a small amount of a balanced fertilizer. It will take a while for the foliage to sprout again, but then it will be ready for the summer garden. If you plant it in a water feature, be sure to cover the bottom of the container with at least 5 inches of gravel to keep the soil firmly in the pot.

Wintering Canna: practical tips to make the job easier.

How to overwinter the beautiful cannas

  • If you are using a garage or other space, start making room in late summer.
  • Look for multi-tiered rolling carts so you can keep all your dormant plants in one place and easily put them away when needed.
  • Turn a raised vegetable bed into a mini-greenhouse in early spring with flexible PVC pipe and 6-ml plastic so you can get your cannas growing early.
  • If you have many specimens of a particular variety after many winters, consider overwintering some of the rhizomes in place and covering them with a thick layer of mulch (16-20 cm) – especially if they are in well-drained, sandy soil.