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How to Grow Cannas: A Complete Planting and Care Guide
Cannas have a reputation for being coarse, and it is unfair. Planted badly they flop and look tatty. Planted well they are the most reliable source of height and colour in a late-summer border — three to five feet of paddle-shaped leaves topped with flowers that keep coming until the first frost.
This guide covers what actually decides whether they perform: timing, depth, water, feeding, and the one mistake most people make in autumn.
What a canna actually is
What you buy is a rhizome — a fat, knobbly underground stem, not a true bulb. It stores water and energy, has visible growing points, and cannot survive frozen ground. Everything about growing cannas follows from that: they want warmth, they want moisture in growth, and they want to be lifted before the ground freezes.
When to plant
Wait until the soil has warmed to about 60°F — usually two weeks after the last frost. Cold soil is the single most common reason cannas rot instead of sprouting.
In zones 8–11 you also get an autumn window: plant in October and the rhizomes sit through winter and shoot away in spring. In zones 3–7, start rhizomes in pots indoors four weeks before your last frost to buy back the season.
How to plant, step by step
- Do not pre-soak. A wet rhizome in cold ground is a rotting rhizome.
- Loosen the soil 10 inches deep and dig in compost. Cannas are heavy feeders and thirsty plants.
- Set the rhizome 4–6 inches deep, growing points up. If you cannot tell which end is up, lay it flat and it will sort itself out.
- Space 18–24 inches apart. They clump fast; crowded rhizomes flower less.
- Water once, then wait. No more water until the first shoot breaks the surface.
Water and feed
Once growing, cannas are thirsty. A deep soak twice a week beats a daily sprinkle, and a mulch of compost keeps roots cool and cuts watering by half.
Feed every three weeks until the flowers open, then stop. Extra nitrogen after that gives you leaves instead of flowers — the most common reason a healthy-looking canna never blooms.
Height, staking and spacing
Most garden varieties reach 3–5 feet without staking, provided they get full sun. In shade they stretch and flop. If you are planting in an exposed spot, put them where a wall or taller shrub breaks the wind rather than reaching for a stake.
Pots
Cannas are excellent in containers — one rhizome in a 12-inch pot, three in an 18-inch pot. Use a heavy compost so the pot does not blow over, and expect to water daily in hot weather. Dwarf varieties stay around 2–3 feet and are the better choice for a patio.
After flowering: the step people skip
Leave the foliage until the first frost blackens it. The leaves are still feeding the rhizome for next year — cutting them back in September is why a lot of cannas flower well once and then fade in later seasons.
- Zones 8–11: cut back after frost, mulch 4 inches deep, leave in the ground.
- Zones 3–7: lift with a fork, shake off (don’t wash) the soil, dry for a week, store in barely-damp peat at 45–55°F. Check monthly and bin anything soft.
Problems you will run into
| No flowers, only leaves | Too much shade, too much nitrogen, or rhizomes that are still sizing up. |
| Yellow, drooping leaves | Usually waterlogging, not drought. Check drainage before watering more. |
| Rotting rhizome | Bacterial soft rot from cold, wet soil. Discard it — it will not recover and it spreads in storage. |
| Canna leaf roller | Rolled leaves with a caterpillar inside. Cut the leaf off and destroy it; no spray needed. |
Choosing a colour
Colour matters more than most people expect, because cannas are large enough to set the tone of a whole border.
- Red reads as formal and stops the eye — use it at the end of a path or either side of a door. Red canna bulbs
- Pink is the quietest and the easiest to blend — good next to silver foliage or a white border. Pink canna bulbs
- Orange carries late summer, especially the speckled leopard types. Orange canna bulbs
- Yellow is the brightest thing in the garden in August — pair with blue or white, never pastel. Yellow canna bulbs
Shop the rhizomes
Canna Lily Bulbs – Pick Your Color
Red, pink, orange or yellow. Packs of 1–5 rhizomes from $12.10.
Frequently asked questions
Do cannas come back every year?
In zones 8–11, reliably. In colder zones you lift and store the rhizomes over winter, or grow them as annuals.
How tall do cannas grow?
Most varieties reach 3–5 feet. Dwarf types stay at 2–3 feet and work well in large pots.
Do cannas need full sun?
Yes — at least six hours. They flower poorly in shade and the stems stretch and flop.
When do cannas bloom?
60–90 days after planting, then continuously until the first frost.
Are cannas toxic to pets?
No, cannas are not listed as toxic to cats or dogs, unlike many tropical plants.