OrnamentalbulbousStraightforward

Crocosmia

Crocosmia × crocosmiiflora

Arching sprays of hot orange or red over stiff pleated fans of leaves in late summer, thriving on neglect. Its reputation is mixed for a good reason: the common naturalised montbretia is genuinely invasive in the wild, while the named garden cultivars are well-mannered clump-formers.

Position: Full sun or Partial shade
Water: moderate demand
Drainage: Moisture-retentive, Free-draining
Grows to: 60–120 cm × 20–40 cm
Hardiness: H5
Flowers: July to September
Difficulty: Straightforward

August

In flower

Crocosmia’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.

Activity	M	A	J	A	S
Plant	March.	April.
In flower			July.	August.	September.
Divide	March.	April.

Names that cause confusion

montbretia — Usually means the vigorous naturalised hybrid Crocosmia × crocosmiiflora, which is a listed invasive non-native in Britain and should not be planted or dumped in the wild. The large-flowered garden cultivars such as 'Lucifer' are far better behaved.

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, Partial shade
Frost: Hardy
Hardiness rating: H5 (RHS)
Grows best at: 12–26 °C
Soil: Loam, Sandy, Clay
Soil pH: 5.5–7.5
Drainage: Moisture-retentive, Free-draining
Water needs: moderate
Drought: moderate tolerance
Waterlogging: moderate tolerance
Heat: good tolerance
Wind and exposure: good tolerance

Where these figures come from

LightSourced guidancemoderate confidence: Royal Horticultural Society: Crocosmia — position
Checked 2026-08-13
FrostSourced guidancehigh confidence: Royal Horticultural Society: Crocosmia — 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: Crocosmia — temperature
Checked 2026-08-13
SoilSourced guidancemoderate confidence: Royal Horticultural Society: Crocosmia — soil
Checked 2026-08-13
Soil pHSourced guidancemoderate confidence: Plant Finder — Missouri Botanical Garden: Crocosmia — culture
Checked 2026-08-13
DrainageSourced guidancemoderate confidence: Royal Horticultural Society: Crocosmia — soil
Checked 2026-08-13
Water needsHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
DroughtHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
WaterloggingHorticultural consensusmoderate confidence: 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: 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.

Soil	Verdict	Why
Heavy clay	Works, with one condition	Crocosmia will crop on heavy clay, but one thing has to be dealt with first. It needs ground that drains, and this soil holds water. A plant that stays in the ground through winter with its roots in cold, saturated soil rots — which is what kills most of what fails on heavy ground, rather than the cold.Improve the drainage before planting — a raised bed, or bulky organic matter worked in over several seasons. Do not add sand to clay in small quantities; it makes the problem worse.
Sandy	Prefers this soil	Sandy suits Crocosmia as it stands: The pH suits it: it wants 5.5 to 7.5, and this soil is in that range. The free drainage is exactly what it wants. Sandy soil is among the soils it is recorded as suiting.
Chalky and alkaline	Grows well here	Crocosmia grows perfectly well on chalky and alkaline without special measures, though it is not the soil it would choose.
Loam	Prefers this soil	Loam suits Crocosmia as it stands: The pH suits it: it wants 5.5 to 7.5, and this soil is in that range. The free drainage is exactly what it wants. Loam is among the soils it is recorded as suiting. The soil holds moisture, which saves a great deal of watering.
Silty	Prefers this soil	Silty suits Crocosmia as it stands: The pH suits it: it wants 5.5 to 7.5, and this soil is in that range. The free drainage is exactly what it wants. The soil holds moisture, which saves a great deal of watering.
Peaty and acid	Works, with one condition	Crocosmia will crop on peaty and acid, but one thing has to be dealt with first. It needs ground that drains, and this soil holds water. A plant that stays in the ground through winter with its roots in cold, saturated soil rots — which is what kills most of what fails on heavy ground, rather than the cold.Improve the drainage before planting — a raised bed, or bulky organic matter worked in over several seasons. Do not add sand to clay in small quantities; it makes the problem worse.
Shallow over rock	Prefers this soil	Shallow over rock suits Crocosmia as it stands: The free drainage is exactly what it wants. Loam is among the soils it is recorded as suiting.
Made ground and urban soil	Works, with one condition	Crocosmia will crop on made ground and urban soil, but one thing has to be dealt with first. It needs ground that drains, and this soil holds water. A plant that stays in the ground through winter with its roots in cold, saturated soil rots — which is what kills most of what fails on heavy ground, rather than the cold.Improve the drainage before planting — a raised bed, or bulky organic matter worked in over several seasons. Do not add sand to clay in small quantities; it makes the problem worse.

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

Space and spacing

Mature height: 60–120 cm
Mature spread: 20–40 cm
Rooting depth: 25 cm
Spacing: 15–25 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: Crocosmia — spacing
Checked 2026-08-13

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: 10 litres or more
Minimum depth: 30 cm

Where the container figures come from

Minimum volumeHorticultural consensusmoderate confidence: Royal Horticultural Society: Crocosmia — cultivation
Checked 2026-08-13
Minimum depthHorticultural consensusmoderate confidence: Royal Horticultural Society: Crocosmia — cultivation
Checked 2026-08-13

Works in a large pot and a pot has one real advantage — the vigorous varieties spread hard in open ground and a container stops that. The clump is dense and dries out quickly in summer, so expect to water. Divide and repot every second or third year, because the corm chain rises and a congested pot flowers poorly.

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: Workable in a container, with conditions

Where these figures come from

In a containerHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13

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: Corm
Survives winter in the ground: Yes — plant once and leave it
Planting depth: 8–10 cm
Naturalises: Increases and spreads where it is happy

Where these figures come from

Storage organSourced guidancehigh confidence: Royal Horticultural Society: Crocosmia × crocosmiiflora — propagation
Checked 2026-08-13
Survives winter in the groundSourced guidancehigh confidence: Royal Horticultural Society: Crocosmia × crocosmiiflora — hardiness
Checked 2026-08-13
Planting depthSourced guidancemoderate confidence: Royal Horticultural Society: Crocosmia × crocosmiiflora — planting depth
Checked 2026-08-13
NaturalisesHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13

A solid swollen stem base, not layered. The old corm is used up each season and a new one forms on top of it, often with small cormlets around the base that take a year or two to reach flowering size.

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.

After flowering. Each corm is replaced annually by a new one on top of the old, so a clump builds a vertical chain and gradually rises out of the ground — which is why an old planting flowers less and looks stranded. Lift, split and replant at depth every third or fourth year.

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.

Method	Suitability	What it needs
Open ground	Well suited source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13
Traditional dug bed	Well suited source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13
Raised bed	Well suited source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13
Container	Workable source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13

Growing it

PropagationLift and divide every few years. Each corm is replaced annually by a new one on top of the old, so a clump builds a vertical chain of spent corms and gradually rises out of the ground — which is why an old planting flowers less and looks stranded on the surface. Splitting it and replanting at proper depth restores it completely.
ProtectionNever dispose of crocosmia in a hedgerow, on a verge or in a green-waste heap that will be spread. Crocosmia × crocosmiiflora is established across western Britain and Ireland from exactly that route, and it displaces native vegetation on banks and cliffs.
WateringAn established clump needs no watering — crocosmia is one of the toughest things in the border and in the right soil is closer to a nuisance than a worry. Water a new planting through its first summer while it roots, and water pots, which dry quickly because the clump is dense. In very dry summers the flower spikes on an unwatered clump come shorter and fewer, which is the plant economising rather than suffering. It does not want winter wet, and a corm chain sitting in cold sodden clay is the one thing that will actually kill it.
FeedingRarely needed and easy to regret. Crocosmia in fed, rich soil makes a great deal of leaf and flops, and the varieties that spread readily spread faster. Where an old clump is flowering poorly the answer is division rather than fertiliser: each corm is replaced annually by a new one on top of the old, so a long-established planting is a vertical chain slowly rising out of the ground with the working corm stranded near the surface. Lift it, take the top corms, discard the spent chain and replant deeper.

Where this guidance comes from

PropagationSourced guidancehigh confidence: Royal Horticultural Society: Crocosmia — division
Checked 2026-08-13
ProtectionSourced guidancehigh confidence: Royal Horticultural Society: Invasive non-native plants
Checked 2026-08-13
WateringSourced guidancehigh confidence: Royal Horticultural Society: Crocosmia — cultivation
Checked 2026-08-13
FeedingSourced guidancemoderate confidence: Royal Horticultural Society: Crocosmia — cultivation
Checked 2026-08-13

The rule is the same in all four: the new piece needs both a growing point and roots of its own. A cutting is the exception that has to make its roots afterwards, which is why the node matters so much.

What goes wrong

Problem	How often	Notes
Congested bulb clump	common source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13

Sources for this page

GrowingHQ editorial synthesis · Plant Finder · Royal Horticultural Society

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.