Cannas: A Historical Lesson for Growing and Overwintering Them Indoors and Out

Cannas are bold, tropical-looking plants with paddle-shaped leaves and spikes of bright flowers. Gardeners in cold-winter regions often treat them as annuals, buying fresh rhizomes each spring. But a historical practice—lifting and storing those rhizomes over winter—explains why cannas are both reliable garden plants and excellent houseplants for a sunny window. Understanding how cannas were managed in the past clarifies what they need today, whether you grow them in a border, a patio pot or a sunlit room.

A short history of a long garden life

Cannas reached European gardens from the Americas in the sixteenth century and became fashionable conservatory plants. In an era when heated glasshouses were expensive, gardeners kept cannas in large pots that moved between the conservatory and the summer border. The plants were valued for their lush foliage and for flowering over a long season. The practical insight from that system is simple: cannas are not delicate. They are vigorous perennial plants that respond to warmth, sun and generous moisture. Treating them as movable plants—inside in the cold months, outside in summer—was not a workaround but a genuine way to enjoy them for years.

That same logic applies today. In hardiness zones where winter temperatures drop below freezing, cannas can be lifted and stored dry, or grown in containers and brought indoors. In frost-free climates, they stay in the ground and multiply into large clumps. The historical greenhouse practice still points to the most flexible method for home gardeners.

Cannas as outdoor summer performers

Cannas grow from thick underground stems called rhizomes. They send up upright stems with broad leaves that unfurl from the centre, creating a column of tropical foliage. In summer, these stems produce clusters of flowers in shades of red, orange, yellow, pink or cream. Flowering continues over weeks rather than all at once, especially if older flower heads are removed before they set seed.

Outdoors, cannas need full sun for the strongest stems and the most flowers. They tolerate partial shade but grow leggier and bloom less. Soil should be rich and moisture-retentive. Cannas are heavy feeders in active growth; a slow-release fertilizer at planting plus occasional liquid feeding keeps leaf colour strong and flowering steady. Water deeply when the top few centimetres of soil dry, but do not leave rhizomes sitting in waterlogged ground, which can encourage rot.

For borders, cannas create a strong architecture: tall cultivars work as the back layer, while compact ones suit the middle or a large patio pot. Their bold leaves contrast well with fine-textured plants such as grasses or small-flowered perennials. Where space is tight, a container restricts size, but the plant still needs a generous pot—cannas are vigorous rooters.

Moving cannas indoors for winter

The historical conservatory model translates easily to a bright room or sunroom. Before the first frost, move container-grown cannas indoors. A cool, frost-free room is ideal for semi-dormancy, but cannas can also be kept actively growing on a sunny windowsill. The key distinction is warmth and light. In a cool room, let the plants rest: water sparingly, and foliage may die back naturally. In a warm, bright position, continue regular watering and feeding, and you may get winter flowers. Either method works if you match care to the plant's state.

If you lift rhizomes from garden beds, trim the stems to about ten centimetres, shake off loose soil and let them dry for a day or two out of direct sun. Store them in a frost-free, dark place in slightly damp peat-free compost, sand or sawdust, checking occasionally for shrivelling or mould. Do not let them freeze, and do not keep them soaking wet. This dry-storage method is what made cannas practical for unheated gardeners in the past, and it remains the most space-efficient way to keep a collection over winter.

Planting and propagating for more plants

Cannas multiply by division of the rhizome. In spring, or when moving container plants, separate rhizomes with at least one healthy growth bud or eye. Use a sharp knife, dust cuts with sulphur if desired, and pot divisions individually. Start them in warmth, about twenty to twenty-five degrees Celsius, in a light, moist potting mix. New shoots appear within a few weeks. This is also how to increase a favourite cultivar; seed-grown cannas vary.

In the garden, plant rhizomes after the last frost when the soil has warmed. A depth of five to ten centimetres protects them from cool nights. For container display, choose a pot at least forty centimetres across for a single compact canna, or larger for a mixed planting. Use a peat-free, free-draining but moisture-retentive medium and add slow-release fertilizer.

Choosing cannas and useful tools

Cultivars differ in height, flower colour and leaf colour. Tall red-flowered kinds suit the back of a border; orange and yellow types glow in low evening light. Dark-leaved cannas, with burgundy or bronze foliage, add contrast even before flowers open. For a small balcony, compact cultivars stay manageable. When buying rhizomes, look for firm, plump pieces with visible eyes. Mail-order rhizomes are convenient, but inspect on arrival and discard any soft, rotting pieces.

Useful equipment makes the indoor-outdoor routine easier. A root-pruning or deep pot with handles simplifies moving plants under cover. A moisture metre removes guesswork from winter watering of dormant rhizomes—use it to confirm the storage medium is barely moist, not wet. A soil thermometer helps you time spring planting: cannas need soil above roughly fifteen degrees Celsius to start quickly. These tools are not gimmicks; they solve the two real risks in canna growing: rot from waterlogged roots and cold from early planting.

Pests, diseases and realistic limitations

Cannas are generally robust, but indoor plants may attract spider mites in dry air, and outdoor plants can suffer slug damage on new shoots. Provide good air circulation indoors and inspect leaf undersides when foliage loses colour. In warm spells, the plants are thirsty—do not let containers dry to the point of wilting. One limitation worth knowing: cannas grown as houseplants need a bright, direct-light position for at least several hours a day. In low light they will persist but will not flower well. Match your space honestly before buying.

None of this is complicated. The historical lesson is that cannas repay a simple routine of lifting, storing and replanting. Whether they spend winter in a conservatory, a spare room or a dry box in the shed, the same principle holds: keep the rhizome alive and off cold, wet ground, then give it summer sun and ample water. That cycle explains why a plant once treated as a glasshouse treasure can be a straightforward resident of garden beds, patio pots and bright windowsills today.