OrnamentalgroundcoverStraightforward

Hardy geranium

Geranium × oxonianum

The most useful herbaceous perennial in a British garden, and the least discussed. It flowers for months, smothers weeds, grows in sun or shade, needs no staking, and responds to a single hard cut in July by producing an entirely fresh mound of leaves and a second flowering.

Position: Partial shade or Full sun or Dappled shade
Water: low demand
Drainage: Moisture-retentive, Free-draining
Grows to: 30–60 cm × 45–90 cm
Hardiness: H7
Flowers: May to September
Difficulty: Straightforward

August

In flower

Coming next month: plant, divide.

Hardy geranium’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	M	J	J	A	S	O
Plant	March.	April.					September.	October.
In flower			May.	June.	July.	August.	September.
Prune					July.
Divide	March.	April.					September.

Names that cause confusion

geranium — Almost always means Pelargonium in a garden centre — the tender bedding and windowsill plants. True Geranium is a fully hardy herbaceous perennial and the two are not interchangeable in any respect.

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: Partial shade, Full sun, Dappled shade
Frost: Very hardy
Hardiness rating: H7 (RHS)
Grows best at: 8–26 °C
Soil: Loam, Clay, Chalky, Sandy
Soil pH: 5.5–7.8
Drainage: Moisture-retentive, Free-draining
Water needs: low
Drought: good tolerance
Waterlogging: moderate tolerance
Heat: good tolerance
Wind and exposure: good tolerance

Where these figures come from

LightSourced guidancemoderate confidence: Royal Horticultural Society: Hardy geranium — position
Checked 2026-08-13
FrostSourced guidancehigh confidence: Royal Horticultural Society: Hardy geranium — 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: Hardy geranium — temperature
Checked 2026-08-13
SoilSourced guidancemoderate confidence: Royal Horticultural Society: Hardy geranium — soil
Checked 2026-08-13
Soil pHSourced guidancemoderate confidence: Plant Finder — Missouri Botanical Garden: Geranium × oxonianum — culture
Checked 2026-08-13
DrainageSourced guidancemoderate confidence: Royal Horticultural Society: Hardy geranium — 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	Hardy geranium 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 Hardy geranium as it stands: The pH suits it: it wants 5.5 to 7.8, 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. It stands dry conditions better than most, which this soil will test.
Chalky and alkaline	Prefers this soil	Chalky and alkaline suits Hardy geranium 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 Hardy geranium as it stands: The pH suits it: it wants 5.5 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 Hardy geranium as it stands: The pH suits it: it wants 5.5 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	Hardy geranium 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 Hardy geranium 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	Hardy geranium 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: 30–60 cm
Mature spread: 45–90 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: Hardy geranium — 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.

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.

Foliage: Semi-evergreen — holds its leaves in a mild winter
In a container: Workable in a container, with conditions

Where these figures come from

FoliageSourced guidancehigh confidence: Royal Horticultural Society: Geranium × oxonianum — foliage
Checked 2026-08-13
In a containerHorticultural 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

PruningWhen the plant sprawls and goes tatty in July, cut the entire thing to the ground — leaves, flowers and all. It looks brutal for a fortnight and then produces a completely fresh low mound of foliage and usually a second flowering into autumn. This one technique transforms the plant and almost nobody does it.
PlantingUse it as weed-suppressing groundcover under roses and shrubs, where its habit of flopping outwards is a virtue rather than a nuisance. It is one of very few perennials that flowers well in part shade and covers ground densely enough to keep annual weeds out.
PropagationDivide in autumn or early spring. Lift the clump and pull or cut it into pieces with a growing point and roots on each; the outer sections are younger and establish faster than the woody centre, which is worth discarding. Most hardy geraniums also seed themselves around, and the seedlings of named forms will not match the parent.
WateringWater new plants in their first summer and thereafter only the ones in genuinely dry shade, which is the hardest position any of them are asked to fill. Established hardy geraniums are among the most self-sufficient plants in the border and the vigorous kinds will cover dry ground under shrubs where little else persists. A clump that goes tired, brown and sprawling in midsummer is not usually thirsty — shear the whole thing to the ground and it produces a fresh mound of leaves and often a second flush of flower within a few weeks.
FeedingNot necessary in ordinary soil, and counterproductive in good soil — a fed hardy geranium makes a great deal of leaf and sprawls over its neighbours, which is the usual reason one gets dug out. A spring mulch of garden compost is enough, and is most worth giving to plants in dry shade competing with tree roots. If a long-established clump is flowering less, lift and divide it in autumn or spring rather than feeding it.

Where this guidance comes from

PruningSourced guidancehigh confidence: Royal Horticultural Society: Hardy geraniums — the Chelsea chop and midsummer cut-back
Checked 2026-08-13
PlantingSourced guidancemoderate confidence: Royal Horticultural Society: Geranium — groundcover
Checked 2026-08-13
PropagationSourced guidancemoderate confidence: Royal Horticultural Society: Hardy geraniums — propagation
Checked 2026-08-13
WateringSourced guidancemoderate confidence: Royal Horticultural Society: Hardy geraniums — cultivation
Checked 2026-08-13
FeedingSourced guidancemoderate confidence: Royal Horticultural Society: Hardy geraniums — cultivation
Checked 2026-08-13

The bud you cut to becomes the new shoot, and it grows in the direction it points — which is why an outward-facing bud opens the plant up and an inward-facing one crosses the middle.

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
Spittlebug	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.