Polka dot begonia
Sources last read 14 September 2026.
Difficult One of the harder ones, and one of the reasons the diagnosis tool exists.
Also called trout begonia.
Polka dot begonia is toxic
- Toxic to cats. Toxic principle: Soluble calcium oxalates. Clinical signs: Kidney failure (in grazing animals), vomiting, salivation in dogs/cats. Most toxic part is underground. ASPCA ASPCA names the genus (Begonia spp.), not the species.
- Toxic to dogs. Toxic principle: Soluble calcium oxalates. Clinical signs: Kidney failure (in grazing animals), vomiting, salivation in dogs/cats. Most toxic part is underground. ASPCA ASPCA names the genus (Begonia spp.), 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: Begonia spp (ASPCA, genus only). Citations below point at the name its source uses.
- Light
- Partial shadeRHS · read 13 September 2026
- Water
- Moist but well-drained or 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
- Clay, Loam, Sand; pH Acid or NeutralRHS · read 13 September 2026
- Toxic to cats
- ToxicASPCA names the genus (Begonia spp.), not the species.ASPCA, filed as Begonia spp. · read 13 September 2026
- Toxic to dogs
- ToxicASPCA names the genus (Begonia spp.), not the species.ASPCA, filed as Begonia spp. · 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 polka dot begonia the browning starts furthest from the midrib and works inward, and it crumbles rather than smears. The centre of each leaf blade is untouched.
Transpiration rises as the air dries, and the tissue furthest from a vein loses first. Penn State Extension notes there is no single humidity figure that suits every indoor plant, which is why this site publishes a range rather than a number.
Telling it apart: Whether the damage advances. Dry air marks a leaf and stops; rot keeps going.
Penn State ExtensionPolka dot begonia brown leaf tips and edges: causes- Pale, undersized leaf blades at the tips of the stems
The newest leaf blades on the polka dot begonia are the palest and smallest, and the stems carrying them bend toward the brightest side of the room.
Partial shade is where its source places it. Below that the plant spends stored sugar faster than it makes it, and reaching is what that looks like from outside.
Telling it apart: Whether it leans. A plant reaching for a window is answering a light question, and it leans before it pales.
RHSPolka dot begonia leaves turning yellow: causes- Yellow, limp leaf blades at the base
Yellow spreads upward through the polka dot begonia a few leaf blades at a time, and the compost darkens and stays cold to the touch.
Soil described as moist but well-drained or well-drained is a drainage instruction as much as a watering one. Compost that stays saturated suffocates the fine roots that do the drinking.
Telling it apart: The soil, not the leaf. Wet compost under yellowing leaves points one way and dry compost the other, and the leaves alone will not tell you which.
RHSPolka dot begonia leaves turning yellow: causes
Not sure which it is? Ask the diagnosis questions for Polka dot begonia.
Routine care
- Watering
- Does not cope with constant direct sun or with waterlogging. During growth, water moderately and give a balanced liquid fertiliser at every other watering.RHS · read 13 September 2026
- Feeding
- While growing, water moderately, adding a balanced liquid fertiliser at every other watering.RHS · read 13 September 2026
- Propagation
- Increase from stem cuttings.RHS · read 13 September 2026
- Pruning
- In late spring, shorten overlong canes, leaving 2 or 3 buds.RHS · read 13 September 2026
- Pests and diseases
- Can be troubled by aphids, vine weevil, glasshouse thrips, mites, 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 maculata, the polka dot begonia, is a species of begonia native to southeast Brazil. It grows naturally in the understory of the Atlantic rainforest, with occurrences confirmed in the Brazilian states of Espírito Santo and Rio de Janeiro. It has been introduced into Mexico, Cuba, the Dominican Republic, and Argentina.
From Wikipedia, CC BY-SA 4.0 · read 13 September 2026
- Native range
- Brazil (Rio de Janeiro)World Checklist of Vascular Plants, June 2026 release, CC BY.Kew WCVP · read 13 September 2026BrazilRHS · read 13 September 2026
- Climate
- wet tropicalWorld Checklist of Vascular Plants, June 2026 release, CC BY.Kew WCVP · read 13 September 2026
- Growth form
- shrub or treeWorld Checklist of Vascular Plants, June 2026 release, CC BY.Kew WCVP · read 13 September 2026Bushy (evergreen)RHS · read 13 September 2026
- Size
- Height 0.5-1 metres; spread 0.1-0.5 metres after 2–5 yearsRHS · read 13 September 2026
- Flowering
- Flowers pink in summer; white in summerRHS · read 13 September 2026
Common problems with Polka dot begonia
Other Begonia
Rex begoniaBrown brittle margins with a green centre
- No photograph yetBegonia taliensisSourced care, difficulty not yet judged
Begonia venosaSourced care, difficulty not yet judged
Elephant-Ear BegoniaSourced care, difficulty not yet judged
Iron Cross BegoniaSourced care, difficulty not yet judged
- No photograph yetMaple Leaf BegoniaSourced care, difficulty not yet judged
More of the Begoniaceae family
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.