OrnamentalbulbousSome care needed

Bearded iris

Iris germanica

The classic early-summer border iris, and the plant most often killed by being treated well. It grows from a fat rhizome that must sit ON the soil surface in full sun to bake — mulched, shaded or buried, it produces perfectly good leaves and stops flowering entirely.

Position: Full sun
Water: low demand
Drainage: Free-draining
Grows to: 40–100 cm × 30–45 cm
Hardiness: H7
Flowers: May and June
Difficulty: Some care needed

Described view

A bearded iris rhizome planted with its upper surface exposed above the soil, beside one buried under mulch

August

Plant · Divide

Bearded iris’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	J	J	A	S
Plant			July.	August.	September.
In flower	May.	June.
Divide			July.	August.

Names that cause confusion

iris — Covers plants with completely opposite requirements. Bearded irises grow from surface rhizomes and need a dry sunny baking; Siberian and water irises want damp or wet ground; bulbous reticulata irises are small spring bulbs. Advice for one will kill another.

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: Very hardy
Hardiness rating: H7 (RHS)
Grows best at: 12–28 °C
Soil: Loam, Sandy, Chalky
Soil pH: 6.5–7.8
Drainage: Free-draining
Water needs: low
Drought: good tolerance
Waterlogging: poor tolerance
Heat: good tolerance
Wind and exposure: good tolerance

Where these figures come from

LightSourced guidancemoderate confidence

Royal Horticultural Society: Bearded iris — position

Checked 2026-08-13

FrostSourced guidancehigh confidence

Royal Horticultural Society: Bearded iris — 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: Bearded iris — temperature

Checked 2026-08-13

SoilSourced guidancemoderate confidence

Royal Horticultural Society: Bearded iris — soil

Checked 2026-08-13

Soil pHSourced guidancemoderate confidence

Plant Finder — Missouri Botanical Garden: Iris germanica — culture

Checked 2026-08-13

DrainageSourced guidancemoderate confidence

Royal Horticultural Society: Bearded iris — 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

Rhizome rot follows wet ground quickly.

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	Bearded iris 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 Bearded iris as it stands: The free drainage is exactly what it wants. Sandy soil is among the soils it is recorded as suiting. It stands dry conditions better than most, which this soil will test.
Chalky and alkaline	Prefers this soil	Chalky and alkaline suits Bearded iris as it stands: The free drainage is exactly what it wants. Chalky soil is among the soils it is recorded as suiting. It stands dry conditions better than most, which this soil will test.
Loam	Prefers this soil	Loam suits Bearded iris as it stands: The pH suits it: it wants 6.5 to 7.8, 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 Bearded iris as it stands: The pH suits it: it wants 6.5 to 7.8, 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	Bearded iris 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 Bearded iris as it stands: The free drainage is exactly what it wants. Loam is among the soils it is recorded as suiting. It stands dry conditions better than most, which this soil will test.
Made ground and urban soil	Works, with one condition	Bearded iris 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: 40–100 cm
Mature spread: 30–45 cm
Rooting depth: 25 cm
Spacing: 30–45 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: Bearded iris — 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: 25 cm

Where the container figures come from

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

Awkward in a pot and worth saying so: the rhizome has to sit on the surface in full sun and bake, the leaves are large for the root volume, and a container that is watered as a container normally is will rot it. If you do grow one, use a wide shallow pot, a very gritty loam-based compost, put the rhizome on top with only the roots buried, and keep it 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: Not a realistic container plant

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: Rhizome
Survives winter in the ground: Yes — plant once and leave it
Planting depth: 0–0 cm
Naturalises: Stays where it is put

Where these figures come from

Storage organSourced guidancehigh confidence: Royal Horticultural Society: Iris germanica — propagation
Checked 2026-08-13
Survives winter in the groundSourced guidancehigh confidence: Royal Horticultural Society: Iris germanica — hardiness
Checked 2026-08-13
Planting depthSourced guidancemoderate confidence: Royal Horticultural Society: Iris germanica — 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.

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. Never mulch over the rhizome. It must sit on the surface and bake through the summer to initiate flower buds, and a plant covered by compost, bark or an encroaching neighbour makes healthy leaves and stops flowering — which is nearly every complaint about a non-flowering iris.

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	Marginal source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13

Growing it

PlantingSet the rhizome so its top is exposed to the sun with the roots spread beneath it, and never mulch over it. A bearded iris needs the rhizome baked through the summer to initiate flower buds, so covering it — with compost, with bark, or with an encroaching neighbouring plant — produces a healthy clump of leaves that never flowers again. Nearly every complaint about a non-flowering iris is this.
PropagationDivide in mid to late summer, cutting the rhizome with a knife rather than pulling it apart. Keep the young vigorous outer sections with a fan of leaves attached, trim the leaves back by half so the wind does not rock them before they root, and throw the old woody centre away.
WateringDo not water an established bearded iris, and take some care not to water near one. The rhizome sits on the surface on purpose and has to bake dry through the summer to set flower buds for the following year, so this is a plant that should be kept out of borders on an irrigation line and away from anything that gets a regular soaking. Water a newly planted rhizome only enough to settle it while the roots take, in its first few weeks. Soft rot at the rhizome — a smelly, slimy patch rather than a dry one — is a wet, shaded, mulched-over rhizome almost every time.
FeedingFeed low and never with nitrogen. A light dressing of sulphate of potash in early spring and again after flowering is the standard and is enough; a general-purpose or high-nitrogen fertiliser produces broad soft leaves, no extra flowers and a marked increase in rot. Keep the feed off the rhizome itself and work it into the soil around the roots. If an old clump has stopped flowering the cause is almost never hunger — it is congestion, or shade, or a rhizome that has been buried by mulch and neighbours.

Where this guidance comes from

PlantingSourced guidancehigh confidence: Royal Horticultural Society: Bearded iris — planting depth
Checked 2026-08-13
PropagationSourced guidancehigh confidence: Royal Horticultural Society: Bearded iris — division
Checked 2026-08-13
WateringSourced guidancehigh confidence: Royal Horticultural Society: Bearded iris — cultivation
Checked 2026-08-13
FeedingSourced guidancehigh confidence: Royal Horticultural Society: Bearded iris — 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
Iris rhizome rot	occasional source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13	A buried or damaged rhizome turns to foul-smelling slime.
Planted at the wrong depth	common source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13
Natural summer dormancy	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.

If something is wrong with it

Leaves yellowing and flopping after flowering — 2 causes GrowingHQ holds for bearded iris

Something else? Work through it with the diagnostic tool.