Rex begonia
Sources last read 14 September 2026.
Difficult One of the harder ones, and one of the reasons the diagnosis tool exists.
Also called fan plant and painted-leaf begonia.
Rex begonia is toxic
- Toxic to cats. Contains soluble calcium oxalates, most concentrated in the parts below ground. Dogs and cats may vomit and drool; kidney failure is recorded in grazing animals. ASPCA
- Toxic to dogs. Contains soluble calcium oxalates, most concentrated in the parts below ground. Dogs and cats may vomit and drool; kidney failure is recorded in grazing animals. ASPCA
- 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.
If your pet ate this plant, call your vet or a pet poison hotline right away.
What the sources say about its care
- Light
- 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.
H1B — 10–15°C 10–15 °CRHS · read 13 September 2026- Soil
- Chalk, Loam, Sand; pH Acid or Alkaline or NeutralRHS · read 13 September 2026
- Toxic to cats
- Contains soluble calcium oxalates, most concentrated in the parts below ground. Dogs and cats may vomit and drool; kidney failure is recorded in grazing animals.ASPCA · read 13 September 2026
- Toxic to dogs
- Contains soluble calcium oxalates, most concentrated in the parts below ground. Dogs and cats may vomit and drool; kidney failure is recorded in grazing animals.ASPCA · read 13 September 2026
- Harmful to people
- No harm is recorded, only a note: the bulbs are ornamental and should not be eaten. Use gloves and protective gear when handling it.RHS · read 13 September 2026
How it usually goes wrong
- Brown brittle margins with a green centre
On a rex begonia the browning starts furthest from the midrib and works inward, and it crumbles rather than smears. The centre of each leaf is untouched.
Leaf margins are the end of the water supply, so they are the first tissue to run short when the air takes more than the roots can send. Penn State Extension cites 30% to 60% as the recommended indoor range, and a heated room in winter sits below it.
Telling it apart: Whether the damage advances. Dry air marks a leaf and stops; rot keeps going.
Penn State ExtensionDiagnose brown tips and edges on this Rex begonia- Leaves soften and curl inward
The rex begonia hangs evenly all over, and the potting mix has gone pale and hard. Nothing is spotted or rotten; the plant is simply short of water.
Water stored in the leaves is spent first and the tissue creases as it empties. That is the reserve doing its job rather than the plant failing.
Telling it apart: Whether water runs straight through. Potting mix dried hard sheds water down the sides, which is itself a sign of drought.
RHSDiagnose a soft, mushy stem on this Rex begonia- Long bare stretches of stem between leaves
Nothing browns and nothing drops; the rex begonia simply makes less, and what it makes is stretched and thin.
Its source places it in partial shade. In less light than that the plant cannot fund full-sized leaves, so it makes smaller ones and spends the difference on stem.
Telling it apart: What the newest growth looks like beside the oldest. Light changes what arrives next; feeding changes what is already on the plant.
RHSDiagnose leggy growth on this Rex begonia
Not sure which it is? Ask the diagnosis questions for Rex begonia.
Routine care
- Propagation
- Increase from seed, leaf cuttings or rhizome sections.RHS · read 13 September 2026
- Pruning
- Pruning is not needed.RHS · read 13 September 2026
- Pests and diseases
- Can be troubled by aphids, vine weevil, thrips, tarsonemid mite, mealybugs and caterpillars. Diseases: rhizome rot, stem rot, powdery mildews and grey moulds.RHS · read 13 September 2026
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Photographs
About the plant
Begonia rex, the king begonia, fancy-leaf begonia, or painted-leaf begonia is a species of flowering plant in the family Begoniaceae. It is a rhizomatous begonia first brought to England from Assam, and documented in 1857.
From Wikipedia, CC BY-SA 4.0 · read 13 September 2026
- Native range
- S. Bhutan to N. MyanmarWorld Checklist of Vascular Plants, June 2026 release, CC BY.Kew WCVP · read 13 September 2026AssamRHS · read 13 September 2026
- Climate
- subtropicalWorld Checklist of Vascular Plants, June 2026 release, CC BY.Kew WCVP · read 13 September 2026
- Growth form
- rhizomatous geophyteWorld Checklist of Vascular Plants, June 2026 release, CC BY.Kew WCVP · read 13 September 2026Clump forming (evergreen)RHS · read 13 September 2026
- Size
- Height 0.1-0.5 metres; spread 0.1-0.5 metres after 2–5 yearsRHS · read 13 September 2026
- Flowering
- Flowers pink in winterRHS · read 13 September 2026
Common problems with Rex begonia
Other Begonia
Plants with similar care
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.