Identity & taxonomy
- Scientific name
- Begonia masoniana Irmsch. ex Ziesenh.
- Family
- Begoniaceae
- Genus
- Begonia
- Order
- Cucurbitales
- IUCN status
- Vulnerable (VU)
- Wikidata
- Q4881894
- Iron cross begoniaen
- Mason's begoniaen
- Järnkorsbegoniasv
- Jernkors-begoniano
- Jernkors-begoniada
- Rautaristibegoniafi
- Eisernes-Kreuz-Begoniede
Southern China (Guangxi) · Northern Vietnam
How to identify it
Growth habit. Rhizomatous begonia with a creeping above-ground rhizome that produces leaves on individual long petioles. The rhizome creeps slowly along the soil surface (3–6 cm per year indoors), producing new leaves at intervals. Older leaves yellow and detach from the rhizome over time. Mature plants form a low spreading mound 30–45 cm wide. Small pink-and-white flowers occasionally appear on long stalks above the foliage in late spring — minor ornamental value compared to the foliage.
Leaves. Heart-shaped (cordate) leaves 15–25 cm long and 12–20 cm wide on long red-tinged petioles 15–25 cm. Upper surface is bright apple-green with a distinctive deep chocolate-brown five-armed pattern radiating from the leaf base — resembling the German Iron Cross or Maltese Cross. Surface texture is bullate (covered in small puckered bumps) — a 3D quilted appearance that catches light dramatically. Underside is paler with prominent reddish veins. Margins are toothed and slightly hairy.
Flowers. Small pink-and-white five-petalled flowers 10–15 mm across on tall flowering stalks in late spring. Flowers carry minor ornamental value compared to the foliage and many growers cut flower stalks off to direct energy back into leaf production.
- Apple-green leaves with chocolate-brown five-armed iron-cross pattern.
- Bullate (puckered/blistered) leaf surface texture.
- Rhizomatous habit — creeping above-ground rhizome, no upright stem.
- Heart-shaped leaves on long red-tinged petioles.
- Toothed slightly hairy leaf margins.
Commonly confused with
Rex begonia
Hundreds of cultivars with vivid silver, pink, purple, and red leaf patterns — but never the simple chocolate-brown five-armed cross of masoniana on apple-green ground. Rex begonias also tend to have less-puckered, more painted-looking surfaces.
Eyelash begonia
Smaller plant with leaves featuring chocolate-brown markings around the leaf margin and along veins, but the marking is around the leaf edge rather than radiating from the base. Distinctively hair-fringed (eyelash) leaf margin.
Polka dot begonia
Tall upright cane begonia, NOT rhizomatous. Asymmetrical wing-shaped leaves with white spots on dark green and bright red underside. Completely different growth habit and leaf shape.
Tiger paws begonia
Small rhizomatous begonia with brown markings on green leaves but in a paw-print spotted pattern, not a centred five-armed cross. Smaller leaves overall.
Care
Light
Bright indirect light; never direct sun.
An east window or 1.5 m back from a south or west window with a sheer curtain. Begonia masoniana is a forest-floor species and burns under direct unfiltered sun within hours. Below 5,000 lux, growth slows dramatically and the iron-cross pattern fades as the plant produces less anthocyanin pigment.
Seasonal: Nordic latitudes above 55°N: dim winters cause some pattern fading. The brightest available indirect spot from October–March keeps the plant in good condition.
Water
Top 2 cm dries — every 5–7 days; water at the rhizome, never the leaves.
Water carefully at the rhizome base, NEVER on the leaves. Wet leaves develop fungal spots within days, and the bullate leaf surface holds water in the puckered bumps where it can sit and rot. Water thoroughly until runoff, then let only the top 2 cm dry. The rhizome itself rots quickly if kept saturated.
Seasonal: Reduce frequency by about a third in winter when growth slows.
Soil
Light, peat-free, fast-draining mix with bark and perlite.
Two parts peat-free houseplant mix, one part fine bark, one part perlite. Begonia masoniana is a rhizomatous begonia from limestone karst — a freely draining habitat. Heavy or compacted soil causes rhizome rot within weeks. The mix should drain water in seconds, not minutes.
Humidity
60–70 %; tolerates 50 % grudgingly.
High humidity is required for the puckered leaves to develop their full ornamental texture. Below 50 % the bullate surface flattens slightly and leaf margins crisp. Run a humidifier nearby through heating season; avoid misting (which puts water on leaves and invites fungal spots — see watering note above).
Temperature
18–24 °C; damage below 15 °C.
A warm-room plant. Cold draughts cause leaf yellowing and drop within days. Below 15 °C the rhizome may go semi-dormant; below 10 °C tissue damage occurs.
Fertilizer
Quarter to half-strength balanced feed monthly in growing season.
A light feeder. Half-strength balanced NPK monthly April–September. Over-fertilising shows as crispy leaf margins and excessive flower stalk production at the expense of foliage. Skip feeding October–March.
Pruning
Remove yellowed leaves and spent flower stalks at the rhizome.
Trim yellowed or damaged leaves at the petiole base, close to the rhizome, with sharp scissors. Cut spent flower stalks at the base. Many growers remove flower stalks as soon as they emerge to direct energy into leaf production. Wear gloves; some people experience contact dermatitis from begonia sap.
Repotting
Every 2 years in spring; use shallow wide pots.
Begonia masoniana has a creeping rhizome that grows horizontally rather than deep. Use shallow wide pots (azalea-style) rather than deep ones — a pot too deep stays wet at the bottom and rots roots. Move up by one pot size in spring.
Leaf cuttings
moderate~8–14 weeks to plantletsThe classic begonia leaf-cutting technique. Cut a healthy leaf with petiole intact, slice across the major veins on the underside (each cut produces a new plantlet), and pin the leaf flat onto moist potting mix or sphagnum, cuts down. Cover with a clear lid for high humidity at 22–25 °C. Plantlets emerge from each cut within 8–14 weeks. Once plantlets have 3–4 leaves, separate and pot individually.
Rhizome division
easy~Immediate; recovery 4–8 weeksAt repotting time, slice through the rhizome with a sharp knife to separate sections, ensuring each division has at least one leaf and a healthy section of root. Pot each into shallow free-draining mix. The most reliable propagation route for amateurs.
Stem cuttings
moderate~6–10 weeksLess common but possible — a section of rhizome with a leaf can be rooted in moist sphagnum at high humidity. The 'wedge cutting' technique using leaf sections with a bit of rhizome attached is a hybrid of leaf cutting and rhizome division.
Common problems
White or grey fuzz on leaves
Symptom
White powdery coating or grey fuzzy patches on leaf surfaces.
Cause
Powdery mildew or botrytis grey mould — both common in begonias with stagnant humid air or wet leaves.
Fix
Remove affected leaves. Improve airflow, never water leaves directly, and reduce overall humidity slightly. Treat remaining plant with a fungicide spray (sulfur-based or neem). Recovery requires changing watering technique to avoid recurrence.
Iron-cross pattern fading
Symptom
New leaves emerge with a much paler or absent brown cross pattern.
Cause
Light too low — anthocyanin pigment production depends on bright light.
Fix
Move to a brighter indirect spot (east window or 1.5 m back from south window with sheer curtain). New leaves emerge with full pattern within 6–10 weeks; existing faded leaves do not regain pattern.
Leaves crisping at margins
Symptom
Brown crispy margins on otherwise healthy leaves.
Cause
Humidity too low, salt build-up from over-fertilising, or fluoride/chlorine in tap water.
Fix
Run a humidifier aiming for 60 %+. Switch to rainwater or filtered water. Flush soil with 3× pot volume of rainwater. Trim crispy margins with scissors following natural leaf shape.
Rhizome going soft and brown
Symptom
The above-ground rhizome turns soft, brown, and mushy; whole sections collapse.
Cause
Rhizome rot from overwatering, soil too heavy, or pot too deep.
Fix
Lift the plant, cut away all rotted rhizome with a sharp clean knife, dust cuts with cinnamon or sulphur. Replant healthy sections into shallow wide pots with very free-draining mix. Reduce watering frequency. Severe rot may require salvaging only leaf cuttings.
Whole plant collapsing in winter
Symptom
Leaves yellow and drop rapidly; rhizome looks shrivelled and inactive.
Cause
Cold damage (below 15 °C) or natural semi-dormancy if temperatures dropped briefly.
Fix
Move to a warmer position (18–22 °C). If rhizome is firm but leafless, treat it like a dormant rhizome: water sparingly, hold off feeding, and wait. New leaves often emerge in spring as warmth returns. If rhizome is mushy, take healthy sections as cuttings.
- Mealybugs at petiole bases
- Spider mites in dry winter air
- Fungus gnats in damp soil
- Powdery mildew on leaves
- Botrytis grey mould on damp leaves
- Rhizome rot from overwatering
Toxicity & safety
Sap can cause mild contact dermatitis in sensitive people; ingestion produces oral burning, mild GI upset. Wear gloves during pruning and repotting.
Mechanism: Soluble calcium oxalates
Begonia — North Carolina Extension Gardener Plant ToolboxASPCA classifies all Begonia as toxic to cats. Symptoms include kidney failure (in grazing animals), vomiting, salivation, and oral burning. Soluble calcium oxalate mechanism is more dangerous than the insoluble raphides found in aroids — the oxalate is absorbed and can damage kidneys with sustained exposure.
Mechanism: Soluble calcium oxalates
Begonia — ASPCA Toxic and Non-Toxic PlantsASPCA classifies all Begonia as toxic to dogs. Symptoms include kidney failure, vomiting, salivation, and oral burning. Same mechanism as in cats.
Mechanism: Soluble calcium oxalates
Begonia — ASPCA Toxic and Non-Toxic PlantsWhy iron cross begonia is hard but worth the effort
Begonia masoniana sits in an awkward position on the begonia difficulty spectrum. The flashy, demanding rex begonias are notoriously high-maintenance: they want greenhouse humidity year-round, rot at the slightest soil error, and live for 1–2 years in most homes. The tough, easy-going begonias like Begonia bowerae and the simple cane begonias survive almost any conditions but lack the dramatic patterned leaves people fall in love with.
Iron cross begonia falls between. It has the dramatic patterning — arguably the most striking of any begonia — but doesn't need full greenhouse conditions. With 60 % humidity (achievable with a humidifier), bright indirect light, and careful watering at the rhizome rather than the leaves, it lives 5+ years and grows steadily into an impressive specimen. The trade-off is that it really does need that 60 % humidity; in dry centrally-heated rooms below 45 % the leaves crisp at the margins and the bullate surface flattens.
The single most common kill mechanism is wet leaves. The bullate (puckered) leaf surface holds water in the small bumps, where it sits and grows fungal spots within days. Watering this plant is a hand-skill: a long-spouted watering can to deliver water to the rhizome at soil level, never overhead and never misting. Once you adopt that habit, masoniana becomes one of the more rewarding and longer-lived patterned begonias.
How leaf-cutting propagation works (and why begonias are special)
Begonias are famous in horticulture for being one of the few plant groups that propagate readily from leaf cuttings — a single leaf can produce multiple new plants. Most plants don't do this; cuttings of a leaf alone usually rot without rooting because cells in mature leaf tissue have lost the ability to regenerate roots and shoots. Begonia leaf cells retain that totipotency, especially at the cuts across major veins.
The technique for Begonia masoniana: take a healthy mature leaf with intact petiole. Place the leaf upside-down on a clean surface and slice across each major vein on the underside with a sharp blade — typically 4–6 cuts radiating from the petiole. Each cut will eventually produce a small plantlet. Pin the leaf flat onto moist potting mix or sphagnum, cuts down, with the petiole buried. Cover with a clear lid (a cake dome works) for high humidity at 22–25 °C. Within 8–14 weeks small plantlets emerge from each cut.
Once plantlets have 3–4 of their own leaves, separate them and pot individually. A single Begonia masoniana leaf can yield 4–8 new plants this way. The original donor leaf eventually senesces but can persist for many months while the plantlets establish. This is why begonias are one of the standard species used in school botany lessons on tissue regeneration.
Begonia masoniana was discovered in cultivation by Maurice Mason at his nursery in King's Lynn, Norfolk in 1952, after a friend brought back unidentified plants from Singapore market. The species was not formally described from wild populations until 1972, when Edgar Irmscher and Lyman Smith published the original description from cultivated material — making this a rare case where the type specimen for a species came from horticulture rather than the wild. The wild populations were subsequently located in limestone karst forest in Guangxi, southern China and northern Vietnam.
Frequently asked · 5
Is iron cross begonia (Begonia masoniana) toxic to cats and dogs?+
Yes — toxic to both. ASPCA classifies all Begonia species as toxic, including masoniana. The mechanism is soluble calcium oxalates, which can cause kidney failure with sustained exposure plus immediate vomiting, salivation, and oral burning. Households with pets that graze on plants should choose a non-toxic alternative.
Why are my iron cross begonia leaves getting fuzzy white patches?+
Powdery mildew or botrytis grey mould — both common in begonias with stagnant humid air or wet leaves. Remove affected leaves, improve airflow, never water the leaves directly (only the rhizome), and treat remaining plant with a sulfur-based fungicide. Recovery requires changing watering technique to prevent recurrence.
How do I propagate Begonia masoniana?+
The classic begonia leaf-cutting technique. Cut a healthy mature leaf with petiole, slice across major veins on the underside (4–6 cuts), and pin the leaf flat onto moist potting mix or sphagnum, cuts down. Cover with a clear lid for high humidity at 22–25 °C. Plantlets emerge from each cut within 8–14 weeks; a single leaf yields 4–8 new plants. Rhizome division is also easy at repotting time.
Why is my iron cross begonia's pattern fading?+
Light too low. The chocolate-brown five-armed cross pattern is produced by anthocyanin pigment that the plant only produces under bright light. Move to an east window or 1.5 m back from a south window with a sheer curtain. New leaves emerge with full pattern within 6–10 weeks; faded leaves do not regain colour.
Why is the rhizome of my iron cross begonia going mushy?+
Rhizome rot — the leading killer of this species. Causes: overwatering, soil too heavy, pot too deep, or watering in the centre of the rhizome rather than around it. Lift the plant, cut away all rotted sections with a clean knife, dust cuts with cinnamon, and replant healthy sections in a shallow wide pot with very free-draining mix. Severe rot may require leaf cuttings to save the genetic line.