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OrnamentalbulbousSome care needed

Canna

Canna × generalis

Grown for enormous paddle-shaped leaves — often bronze, purple or striped — with the flowers a bonus on top. It is the plant that makes a British border look subtropical in August, and it is a yearly commitment: the rhizomes are lifted before the first frost or the plant is lost.

Position
Full sun
Water
high demand
Drainage
Moisture-retentive, Tolerates wet ground
Grows to
100–200 cm × 50–80 cm
Hardiness
H3
Harvest
October and November
Difficulty
Some care needed

Described view

A lifted canna rhizome with the stems cut to about 10 cm, sitting in a box of barely-moist old compost, beside a dry-stored dahlia tuber for comparison

August

In flower

Canna’s year

Resolved for United Kingdom (general). Every window is stored against a climate event rather than a date, so a late frost pocket runs later than the band shows. What else August calls for.

ActivityJFMAMJJASOND
PlantMay. June.
In flowerJuly. August. September. October.
HarvestOctober. November.

Names that cause confusion

canna lily — Not a lily and not related to one. Cannas grow from rhizomes and belong to their own family; true lilies are true bulbs in the Liliaceae.

Timing that travels

The band above resolves this plant's windows into months for one region. These are the windows themselves, stored against a climate event rather than a date — which is the form that survives being carried to a colder garden, a frost pocket, or next year.

Conditions it needs

Light
Full sun
Frost
Frost tender
Hardiness rating
H3 (RHS)
Grows best at
16–30 °C
Soil
Loam, Peat-free compost, Silt
Soil pH
6–7.5
Drainage
Moisture-retentive, Tolerates wet ground
Water needs
high
Drought
poor tolerance
Waterlogging
good tolerance
Heat
good tolerance
Wind and exposure
poor tolerance
Where these figures come from
LightSourced guidancemoderate confidence
  • Royal Horticultural Society: Canna — position

Checked 2026-08-13

FrostSourced guidancehigh confidence
  • Royal Horticultural Society: Canna — hardiness

Checked 2026-08-13

Hardiness ratingSourced guidancemoderate confidence
  • Royal Horticultural Society: RHS hardiness ratings

Checked 2026-08-13

Grows best atSourced guidancemoderate confidence
  • Royal Horticultural Society: Canna — temperature

Checked 2026-08-13

SoilSourced guidancemoderate confidence
  • Royal Horticultural Society: Canna — soil

Checked 2026-08-13

Soil pHSourced guidancemoderate confidence
  • Plant Finder — Missouri Botanical Garden: Canna — culture

Checked 2026-08-13

DrainageSourced guidancemoderate confidence
  • Royal Horticultural Society: Canna — soil

Checked 2026-08-13

Water needsHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

DroughtHorticultural consensusmoderate confidence

Large leaves lose water fast; it wants constant moisture.

No external citation — see the evidence type above.

Checked 2026-08-13

WaterloggingHorticultural consensusmoderate confidence

Happy in a wet border or at a pond margin.

No external citation — see the evidence type above.

Checked 2026-08-13

HeatHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Wind and exposureHorticultural consensusmoderate confidence

Big leaves shred in wind.

No external citation — see the evidence type above.

Checked 2026-08-13

On your soil

Computed by comparing this plant's recorded requirements against each soil's recorded characteristics. A recorded horticultural fact overrides the comparison where GrowingHQ holds one.

SoilVerdictWhy
Heavy clayPrefers this soilHeavy clay suits Canna as it stands: The pH suits it: it wants 6 to 7.5, and this soil is in that range. It tolerates ground that stays wet, which most crops do not. The soil holds moisture, which saves a great deal of watering.
SandyWorks, with one conditionCanna will crop on sandy, but one thing has to be dealt with first. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering.Water and mulch will carry it through. On this soil the watering is not optional in a dry spell, which is the difference between a crop and a failure.
Chalky and alkalineWorks, with one conditionCanna will crop on chalky and alkaline, but one thing has to be dealt with first. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering.Water and mulch will carry it through. On this soil the watering is not optional in a dry spell, which is the difference between a crop and a failure.
LoamPrefers this soilLoam suits Canna as it stands: The pH suits it: it wants 6 to 7.5, and this soil is in that range. Loam is among the soils it is recorded as suiting. The soil holds moisture, which saves a great deal of watering.
SiltyPrefers this soilSilty suits Canna as it stands: The pH suits it: it wants 6 to 7.5, and this soil is in that range. Silt is among the soils it is recorded as suiting. The soil holds moisture, which saves a great deal of watering.
Peaty and acidGrows well hereCanna grows perfectly well on peaty and acid without special measures, though it is not the soil it would choose.
Shallow over rockWorks, with one conditionCanna will crop on shallow over rock, but one thing has to be dealt with first. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering.Water and mulch will carry it through. On this soil the watering is not optional in a dry spell, which is the difference between a crop and a failure.
Made ground and urban soilGrows well hereCanna grows perfectly well on made ground and urban soil without special measures, though it is not the soil it would choose.

Not sure which you have? Four hand tests will settle it.

Space and spacing

Mature height
100–200 cm
Mature spread
50–80 cm
Rooting depth
35 cm
Spacing
45–60 cm apart
Where these figures come from
Mature heightHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Mature spreadHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Rooting depthHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

SpacingSourced guidancemoderate confidence
  • Royal Horticultural Society: Canna — spacing

Checked 2026-08-13

How far apart to plant cannaThree canna plants drawn in a row at their recorded spacing of 45–60 cm between plants. The spacing is drawn to scale against a one metre rule; the plants themselves are symbols rather than scale drawings, so the distance between them is the part to read.45–60 cmone metre
Measured centre to centre. Plants set closer than this compete for light and water long before they look crowded, and the crowding cannot be undone once they are in.

In a container

Minimum volume
25 litres or more
Minimum depth
35 cm
Where the container figures come from
Minimum volumeHorticultural consensusmoderate confidence
  • University of Maryland Extension — University of Maryland: Canna

Checked 2026-08-13

Minimum depthHorticultural consensusmoderate confidence
  • University of Maryland Extension — University of Maryland: Canna

Checked 2026-08-13

A very good container plant and a demanding one. It wants a large pot of rich moisture-retentive compost, generous water all summer and weekly feeding, and it will still be thirstier than anything else on the patio in August. The pot is also how it overwinters: bring it under cover after the first frost blackens the foliage and keep the rhizome barely moist rather than dry.

Habit and ultimate size

What the plant becomes, rather than what it is when you buy it. The gap between the two is where most planting mistakes live.

In a container
Good in a container long-term
Where these figures come from
In a containerHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Bulb, corm, rhizome and tuber comparedFour underground storage organs drawn in section at the same scale. A true bulb is layered scales around a growing point on a flat basal plate, and multiplies by offsets that pull apart by hand. A corm is a solid swollen stem base with a bud on top, the previous year's spent corm beneath it and small cormlets at its sides. A rhizome is a horizontal swollen stem that sits at soil level with roots below and a growing point at one end, and must not be buried. A tuber is a swollen stem with growth buds scattered over its whole surface and no basal plate, so a cut piece without a bud on it cannot grow.True bulbbasal plateDaffodil, tulip, lilyPull offsets apart by hand.Cormspent corm below, cormlets asideCrocus, gladiolus, crocosmiaReplaced yearly by a new one on top.Rhizomesoil level — top stays exposedBearded irisCut with a knife. Must not be buried.Tuberbuds scattered, no basal plateCyclamen, potatoA cut piece without a bud will rot.
All four are sold as 'bulbs'. The differences are internal, which is why they are drawn rather than photographed — and each one changes what you physically do with the thing in your hand.
Storage organ
Rhizome
Survives winter in the ground
No — lift and store, or treat as annual
Planting depth
8–10 cm
Naturalises
Stays where it is put
Where these figures come from
Storage organSourced guidancehigh confidence
  • Royal Horticultural Society: Canna × generalis — propagation

Checked 2026-08-13

Survives winter in the groundSourced guidancehigh confidence
  • Royal Horticultural Society: Canna × generalis — hardiness

Checked 2026-08-13

Planting depthSourced guidancemoderate confidence
  • Royal Horticultural Society: Canna × generalis — planting depth

Checked 2026-08-13

NaturalisesHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

A swollen stem growing horizontally at or just below the surface. Divided with a knife, and the cut piece needs both roots and a growing point. Burying a rhizome that wants to sit in the sun is the commonest reason it stops flowering.

How deep to plant a bulb, drawn to scaleEight geophytes drawn at one scale against a soil surface line, each at the depth the catalogue records for it. A bearded iris rhizome sits on top of the soil with only its roots buried. A cyclamen tuber and a nerine bulb are barely covered, at 2 to 3 centimetres, the nerine with its neck standing proud. Snowdrops and crocuses go at 8 to 10 centimetres, a daffodil at 10 to 15, a tulip at 15 to 20 and a lily deepest at 15 to 25 centimetres. Most sit at roughly two to three times their own height, and the shallow exceptions are shallow because the organ must bake in the sun to flower.soil surface5 cm10 cm15 cm20 cmBearded irison topon the surfaceCyclamen2 cmjust coveredNerine2 cmneck proudSnowdrop9 cmCrocus9 cmDaffodil13 cmTulip18 cmplant deepLily20 cmstem roots
Two to three times the bulb's own height is the working rule, and the four plants that break it are the four most often planted wrong. A bearded iris buried by mulch or a tidy neighbour will make leaves for years and never flower again.
Lifting and storing. Lift after the first frost blackens the foliage, cut the stems back to about 10 cm, and store the rhizomes in barely-moist old compost somewhere frost-free. The distinction that matters is against the dahlia standing next to it: a dahlia tuber is stored dry, and a canna rhizome stored dry shrivels and often fails to shoot.
source

Horticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

After flowering. In a mild sheltered garden with sharp drainage some gardeners leave them out under a thick dry mulch. It works most years, which is a different claim from working.
source

Horticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Where and how you can grow it

Each way of growing is assessed separately, and “not assessed” is a real answer rather than a gap we have filled in with a guess.

MethodSuitabilityWhat it needs
Open groundWell suited
source

Sourced guidancemoderate confidence

  • Royal Horticultural Society: Growing method suitability

Checked 2026-08-13

Traditional dug bedWell suited
source

Sourced guidancemoderate confidence

  • Royal Horticultural Society: Growing method suitability

Checked 2026-08-13

Raised bedWell suited
source

Sourced guidancemoderate confidence

  • Royal Horticultural Society: Growing method suitability

Checked 2026-08-13

ContainerWell suited
source

Sourced guidancemoderate confidence

  • Royal Horticultural Society: Growing method suitability

Checked 2026-08-13

Growing it

  • HarvestingLift after the first frost has blackened the leaves, cut the stems to about 10 cm, and store the rhizomes barely moist in old compost somewhere frost-free. Bone dry kills them, which is the difference between a canna and a dahlia and the commonest reason a stored one fails to shoot.
  • WateringIt is a marginal aquatic in origin and will not be over-watered in summer. A canna in a pot that dries out once has scorched leaf edges for the rest of the season, because the damaged leaves are not replaced.
  • ProtectionLift the rhizomes once the first frost has blackened the foliage and store them in barely damp compost somewhere frost-free at around 7–10 °C — dry storage shrivels them, which is the difference between a canna and a dahlia. In a mild garden with genuinely free-draining soil they can stay in the ground under 15 cm of dry mulch, but a heavy wet winter soil will rot them whatever the temperature does.
  • FeedingCannas are hungry in a way most ornamentals are not: a plant putting up two metres of thick leaf in a single season needs it. Feed a container-grown plant weekly with a balanced liquid feed from May until the end of August, and mulch a border planting with well-rotted manure in spring. Stop feeding in early September — pushing soft growth into autumn on a plant that has to be lifted before the first frost gives you more material to cut off and a rhizome that has moved less of its reserve back into store.
Where this guidance comes from
HarvestingSourced guidancehigh confidence
  • Royal Horticultural Society: Canna — overwintering

Checked 2026-08-13

WateringSourced guidancemoderate confidence
  • Plant Finder — Missouri Botanical Garden: Canna — culture

Checked 2026-08-13

ProtectionSourced guidancehigh confidence
  • Royal Horticultural Society: Canna — overwintering

Checked 2026-08-13

FeedingSourced guidancemoderate confidence
  • University of Maryland Extension — University of Maryland: Canna

Checked 2026-08-13

Harvesting

  • When it is readyThere is nothing to pick — the harvest question for canna is when to lift the rhizomes, and the answer is once the first frost has blackened the foliage, usually October or November. In a mild garden with free-draining soil they can be left in the ground under a thick dry mulch instead, but a wet winter kills more cannas than a cold one.
  • How to pick itCut the stems down to about 10 cm, fork the clump up whole and shake off most of the soil without washing the rhizomes clean. Let them dry for a few days only — canna rhizomes shrivel if dried hard — then pack them in barely damp compost.
  • Keeping itStore in barely moist compost in a frost-free place around 7–10 °C. Unlike dahlias they must not dry out completely; check every few weeks and mist the compost if it goes dust dry.
Where the harvest guidance comes from
When it is readySourced guidancehigh confidence
  • Royal Horticultural Society: Canna — overwintering

Checked 2026-08-13

How to pick itSourced guidancehigh confidence
  • Royal Horticultural Society: Canna — lifting

Checked 2026-08-13

Keeping itHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Safety and edibility

Cats and dogs

Listed as non-toxic to cats and dogs

Canna appears on published non-toxic lists for cats and dogs. That is a statement about the plant's chemistry, not a guarantee: any plant eaten in quantity can upset an animal, so it is still worth discouraging heavy chewing.
source

Sourced guidancehigh confidence

  • ASPCA Animal Poison Control Center — toxic and non-toxic plant list — American Society for the Prevention of Cruelty to Animals: Canna generalis — non-toxic plants list

Checked 2026-08-13

    Sources for this page

    GrowingHQ editorial synthesis · Plant Finder · Royal Horticultural Society · University of Maryland Extension

    Each figure on this page carries its own citation, under the “where these figures come from” note in its section. Record last reviewed 2026-08-14.