Zonal geranium
Sources last read 14 September 2026.
Forgiving Among the more tolerant plants here.
Also called horseshoe geranium and zonal pelargonium.
Zonal geranium is toxic
- Toxic to cats. Toxic principle: Geraniol, linalool. Clinical signs: Vomiting, anorexia, depression, dermatitis. ASPCA ASPCA names the genus (Pelargonium species), not the species.
- Toxic to dogs. Toxic principle: Geraniol, linalool. Clinical signs: Vomiting, anorexia, depression, dermatitis. ASPCA ASPCA names the genus (Pelargonium species), not the species.
- Not assessed for people. RHS publishes no harm statement for this plant. That is not a finding of safety: none of the sources read for this site gives an answer either way. Treat it as unknown.
What the sources say about its care
Sources file this plant under other names: Pelargonium species (ASPCA, genus only). Citations below point at the name its source uses.
- Light
- Full sun, Partial shadeRHS · read 13 September 2026
- Water
- Well-drainedRHS · read 13 September 2026
- Humidity
No source read publishes a humidity figure for any plant on this site. What follows is general guidance for foliage plants.
ASHRAE recommends indoor relative humidity between 30% and 60% 30–60%Penn State Extension · read 13 September 2026- Temperature
How cold this tolerates, not what it prefers. No source read for this site publishes a preferred range for a plant indoors.
H1C — 5–10°C 5–10 °CRHS · read 13 September 2026- Soil
- Loam, Sand; pH Acid or Alkaline or NeutralRHS · read 13 September 2026
- Toxic to cats
- ToxicASPCA names the genus (Pelargonium species), not the species.ASPCA, filed as Pelargonium species · read 13 September 2026
- Toxic to dogs
- ToxicASPCA names the genus (Pelargonium species), not the species.ASPCA, filed as Pelargonium species · read 13 September 2026
- Harmful to people
- No statement of harm to people is published for this plant; that absence is not evidence it is safe.RHS · read 13 September 2026
How it usually goes wrong
- Bleached patches on the side facing the glass
On a zonal geranium the marks are patchy and one-sided. Leaves on the shaded side of the plant keep their colour entirely.
Glass concentrates what would be tolerable outdoors, because it holds the heat and removes the moving air that carried it away. Its source describes full sun, partial shade.
Telling it apart: Whether the undersides are affected. Light damages what it reaches and nothing else.
RHSDiagnose spots on the leaves on this Zonal geranium- Brown tips on the newest leaves first
Leaves on the side of the zonal geranium nearest a heater or vent brown at the edges while those on the far side stay clean.
Dry air takes water from the leaf surface continuously, and the tissue at the edge is last in the queue for what the roots send up. Penn State Extension notes there is no single humidity figure that suits every indoor plant.
Telling it apart: Look at the pot rim and the soil surface. A white crust points at a build-up from tap water or feed rather than at the air. Penn State also reports misting and pebble trays do little to the humidity around a plant.
Penn State ExtensionZonal geranium brown leaf tips and edges: causes- Buds form and fall before they open
The zonal geranium sets buds normally, and they yellow at the stalk and drop before they colour.
Its source places it in full sun, partial shade. A bud formed in that light and then turned away from it, or left in drying compost, is the first thing the plant gives up.
Telling it apart: What happened in the fortnight before the buds dropped. A move, a turned pot or a dry spell is the usual answer.
RHSDiagnose leaf drop on this Zonal geranium- The plant goes limp and the compost shrinks from the pot
The zonal geranium hangs evenly all over, and the compost has gone pale and hard. Nothing is spotted or rotten; the plant is simply short of water.
With well-drained soil taken past dry, there is nothing left for the roots to move, and the plant gives up its shape before it gives up its colour.
Telling it apart: Whether water runs straight through. Compost dried hard sheds water down the sides, which is itself a sign of drought.
RHSZonal geranium drooping or wilting: causes
Not sure which it is? Ask the diagnosis questions for Zonal geranium.
Routine care
- Repotting
- For overwintering, raise small plants from cuttings in late summer, or reduce old plants by a third and lift them to store somewhere frost-free, then repot in spring once growth starts again.RHS · read 13 September 2026
- Propagation
- Root softwood cuttings in summer and keep the plants frost-free over winter, or root softwood cuttings in spring.RHS · read 13 September 2026
- Pruning
- Deadhead often. In spring, old plants can be renewed with a hard cut back.RHS · read 13 September 2026
- Pests and diseases
- Aphids, fungus gnats, thrips, caterpillars, leafhoppers and vine weevil can attack it. Disease risks: a virus, Pelargonium rust, grey moulds, and root and foot rots where soil is wet.RHS · read 13 September 2026
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About the plant
Pelargonium zonale is a species of Pelargonium native to southern Africa in the western regions of the Cape Provinces, in the geranium family. It is one of the parents of the widely cultivated plant Pelargonium × hortorum, often called "geranium", "horseshoe geranium", "zonal geranium" or "zonal pelargonium".
From Wikipedia, CC BY-SA 4.0 · read 13 September 2026
- Native range
- Cape Prov. to KwaZulu-NatalWorld Checklist of Vascular Plants, June 2026 release, CC BY.Kew WCVP · read 13 September 2026Temp S AfricaRHS · read 13 September 2026
- Climate
- subtropicalWorld Checklist of Vascular Plants, June 2026 release, CC BY.Kew WCVP · read 13 September 2026
- Growth form
- subshrub or shrubWorld Checklist of Vascular Plants, June 2026 release, CC BY.Kew WCVP · read 13 September 2026Bushy (evergreen)RHS · read 13 September 2026
- Size
- Height 1-1.5 metres; spread 0.5-1 metres after 2–5 yearsRHS · read 13 September 2026
- Flowering
- Flowers pink in summer; purple in summer; white in summerRHS · read 13 September 2026
Common problems with Zonal geranium
Other Pelargonium
Plants with similar care
Blue passion flowerA thin dry rim that crumbles between the fingers
Bush lilyDry, curled edges on leaves near a heater
Dog roseEdges of the leaves brown while the middle stays sound
English lavenderBuds form and fall before they open
Flaming KatyA thin dry rim that crumbles between the fingers
Hardy fuchsiaBrown, papery patches on the leaves nearest the glass
Sources
- ASPCA · read 13 September 2026
- Kew WCVP · read 13 September 2026
- Penn State Extension · read 13 September 2026
- RHS · read 13 September 2026
- Wikipedia · read 13 September 2026
What this does not cover
The figures above are what published sources say, not measurements of the plant in your room. They say nothing about your pot size, your water, the season, or how far from the glass the plant stands, and those decide more than any figure here does.
Humidity has no species figure because no source read for this site publishes one, and the only temperature published for this plant is a cold floor. The simulator fills those gaps with general figures for its kind of plant, marked as general and listed on how we read sources. Where a toxicity row says the plant was not assessed, that is the absence of a finding and not a finding of safety.
If something is already wrong, the diagnosis tool asks about the soil, the window and the watering, which is where the answer usually is.