Houseplant · Begoniaceae
Rex Begonia
Begonia Rex Cultorum Group
With foliage that reads like fine textile, the rex begonia brings quiet drama to a bright, sheltered corner.
Bright indirect
66–73°F · 19–23°C
USDA 10–11
12–18 in · 30–46 cm
Overview
The rex begonia is a plant of presence, kept for the way its leaves hold a room rather than for any bloom. Its foliage carries silver, plum, rose, and deep green in a swirl that draws the eye without shouting, while the small pink-white flowers stay politely in the background. It belongs to the Rex Cultorum Group, a broad family of hybrids descended from a wild begonia of the eastern Himalayan foothills.
Low and unhurried, it grows from a creeping rhizome and settles at 12 to 18 inches (30 to 46 cm) tall with a matching spread. That compact, spreading habit makes it a natural for a shallow bowl on a console, a shelf, or a side table where its color can do the work of an accent.
None of this comes without attention. The rex begonia is a demanding plant that asks for steady warmth, humid air, and gentle movement around it, and it registers any lapse in the look of its leaves. Given a considered spot and a light hand, it repays the care with a display few houseplants can rival, yet it turns quickly in stale air or wet soil.
Care
The short version: set it in bright, indirect light, keep the soil evenly moist in a porous mix that never turns heavy, hold the room around 66°F to 73°F (19°C to 23°C), and lift the humidity through the surrounding air rather than by wetting the leaves.
Light
Give it bright, indirect light, and spare it hot, direct sun, which scorches the patterned leaves and dulls the effect you keep it for. It manages in partial to full shade, though the color quiets there, and a discreet fluorescent fixture stands in where a window cannot reach.
Water
Keep the soil evenly moist, letting the surface dry a little between waterings, and never leave it standing wet. Water at the soil or from below rather than over the top, since damp leaves undo both the health and the look of the plant. Ease off through the winter rest.
Soil
Plant it in a porous, well-drained mix rich in organic matter, a light soilless or African-violet blend. A slightly acidic pH of 5.5 to 6.5 suits it, and a shallow pot flatters the creeping rhizome far more than a deep one.
Temperature
A steady room between 66°F and 73°F (19°C to 23°C) keeps it at its best, and growth slows once nights fall much below that. Keep it away from cold drafts and abrupt chills.
Humidity
This is a plant for high humidity, around 50% to 75%, more than most rooms hold through winter. Raise it with a pebble tray or by misting the air around the plant, never the leaves, since damp foliage is the quickest route to fungal trouble.
Feeding
Through the spring-to-fall growing season, offer a balanced liquid fertilizer at half strength every couple of weeks at alternate waterings. Set the feeding aside once fall and winter arrive and the plant rests.
Pruning
It asks for little pruning. Lift away dead or ailing leaves as they appear, which keeps the plant looking its best and the air moving against fungus. A pinch at the tips coaxes it to branch and fill its pot.
Repotting
Repot in spring when the roots have filled the pot, choosing a shallow vessel suited to the creeping rhizome. Roots circling the root ball are the signal that a move is due.
Size & spacing
A mature rex begonia stays compact at 12 to 18 inches (30 to 46 cm) tall and about as wide, an easy scale for a tabletop or shelf. Leave a little space on each side so air can move and the leaves stay dry.
Troubleshooting
Most of what unsettles a rex begonia comes back to water and air. Heavy, wet soil and still, damp air open the door to the rots and mildews, while a dim placement drains the color that gives the plant its point. Read the signs below and respond early, while the look is still easy to restore.
A wilting plant over a dark, softened base
Soil that stays soggy brings on crown and root rot. When the rhizome turns soft and dark, stop watering and let the mix dry out. Repot into fresh, porous media in a shallow pot, trim away the rotted tissue, and return to watering with a lighter hand.
Fix:
- Stop watering and allow the mix to dry
- Repot into fresh porous, well-draining mix and a shallow pot, trimming away rotted tissue
- Resume careful watering, avoiding waterlogged soil
A dusty white film that will not rub away
That pale film is powdery mildew, a fungus that arrives where the air is still and the humidity runs high. Take off the marked leaves and open the space so air can circulate around the plant. Keep water off the foliage as well, since wet leaves are what carry it along.
Fix:
- Remove and discard affected leaves
- Improve air circulation around the plant
- Avoid wetting foliage; spray the surrounding air rather than the leaves to raise humidity
A grey, fuzzy mold over softening leaves
This is botrytis, the grey mold that settles where foliage stays wet in stagnant, damp air. Remove the affected parts and discard them rather than composting. Water at the soil instead of overhead, and open up the space around the plant so it can dry.
Fix:
- Remove and destroy affected plant parts
- Increase air circulation and lower ambient moisture on foliage
- Stop misting/wetting leaves; water at the soil
Cottony clusters, fine webbing, or stippled new leaves
A few sap-feeders leave distinct calling cards. Cottony white clusters in the leaf axils mark mealybugs, faint webbing over stippled leaves points to spider mites, and a rise of tiny insects when the plant is disturbed signals whiteflies. Dab the mealybugs with rubbing alcohol, set the plant apart from the rest, and keep treating until they clear.
Fix:
- Dab mealybugs with rubbing alcohol on a cotton swab
- Isolate the plant to prevent spread
- Treat repeatedly until pests are gone, raising humidity to discourage spider mites
Fading pattern and stretched, reaching stems
When the markings pale and the stems reach, the plant is telling you it has too little light. Move it to a brighter position with generous indirect light, keeping it clear of hot, direct sun. Where a window falls short, a fluorescent fixture makes up the difference.
Fix:
- Move to a brighter spot with plenty of bright, indirect light (avoid direct, hot sun)
- Supplement with fluorescent lighting if natural light is limited
Stalled growth and falling leaves in winter
A rex begonia that quiets and sheds leaves in the cold season is simply entering winter dormancy, prompted by shorter days and cooler air. The rhizome holds firm beneath the thinning foliage. Water less, pause feeding until spring, and resume the usual routine when growth picks up again.
Fix:
- Reduce watering and keep the soil barely moist
- Stop fertilizing until new spring growth appears
- Resume normal care when active growth resumes in spring
Toxicity
For all its polish, this is a plant to place with care, because the rex begonia is toxic. Every part holds soluble calcium oxalate, and the hidden rhizome holds the most. A pet that chews the leaves will drool and grow unwell, grazing animals can face kidney effects, and the sap can irritate skin, so give it a home well clear of pets, livestock, and small children.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Moderate
Leaves chewed by a cat tend to bring drooling and vomiting as the calcium oxalate irritates the mouth and stomach. The rhizome underground holds the most, so a cat digging at the base takes a heavier dose.
Dogs Moderate
A dog that mouths the foliage tends to drool, paw at its face, and grow queasy. The greater risk lies in the rhizome, where the toxin is most concentrated.
Horses Severe
Grazing animals come off worst. The soluble oxalates can travel through the body and burden the kidneys, so a horse that browses the plant may end up far sicker than a light taste would suggest.
Rabbits Toxic
Rabbits feed low and steadily, which makes the same kidney-stressing oxalates a true hazard. Keep the plant well beyond their reach and never let any part become food.
Livestock Toxic
Goats, sheep, and cattle share the systemic oxalate risk that affects horses, with mouth irritation and possible kidney trouble following a graze. Fence the plant off completely.
Birds Caution
The oxalates that trouble mammals make the plant a poor companion for pet birds as well. Treat any pecking at the leaves as a concern and keep inquisitive birds away.
People Caution
No part of the plant belongs on a plate, and the sap can leave sensitive skin itchy or rashy after handling. Wash your hands after pruning, and keep small children from bringing leaves to their mouths.
NC State and UConn note the sap contains calcium oxalate and can cause skin irritation/contact dermatitis in some people when handling
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
The Rex Cultorum Group runs to countless named hybrids, every one chosen for its foliage. One earns a mention in the botanical record.
Begonia rex-cultorum 'Super Curl'
A named selection from the much-hybridized Rex Cultorum Group, grown as the whole line is for ornamental patterned leaves rather than for its flowers.
How to propagate
One rex begonia readily becomes several, which makes it easy to carry its look into other corners of a home. The season for it is spring and summer, when the plant is in active growth.
Leaf cuttingsModerate
Spring to summer · Plantlets form in 1-3 months
Leaf cuttings are the route to try in spring or summer, while the plant is in growth. Cut across the major veins on the underside and lay the whole leaf flat on moist media, or divide it into wedges that each keep a main vein. New plantlets rise from the cuts over the next one to three months.
DivisionEasy
At repotting in spring · Several weeks
Division is the simplest approach, done as the plant is repotted in spring. Separate the rhizome into pieces, each keeping its own roots and leaves, and pot them individually. They settle in within a few weeks.
Stem cuttingsModerate
Spring to summer · Several weeks
Stem cuttings taken through the spring and summer season work as well. Root a cutting in moist media and it takes hold within a few weeks.
Myths
Rex begonias are grown mainly for their flowers.
The appeal here is all in the leaves, not the flowers. Their foliage carries the color and pattern that define the plant, while the blooms stay small, pinkish-white, and easy to overlook. A rex begonia earns its place through its leaves.
A begonia's calcium oxalate is the same harmless mouth-irritant found in aroids.
The two differ in a way that matters. Aroids hold insoluble oxalate crystals that sting the mouth and then pass, but the ASPCA identifies the begonia's toxin as soluble calcium oxalate, which the body can absorb. In grazing animals, that can mean kidney failure rather than passing discomfort.
Misting the leaves is the best way to give a rex begonia the humidity it wants.
It seems sensible, yet it works against the plant. Rex begonias do want humid air, but wet leaves invite the very fungi that trouble them, powdery mildew and botrytis in particular. Raise the humidity in the surrounding air instead, with a pebble tray or a light spray of the space nearby. Leave the foliage itself dry.
Sources
- ASPCA Animal Poison Control
- NC State Extension Gardener Plant Toolbox
- Clemson Cooperative Extension HGIC
- Missouri Botanical Garden Plant Finder
- University of Connecticut Home & Garden Education Center
- Pet Poison Helpline
- University of Illinois Extension
- Plants of the World Online, Royal Botanic Gardens Kew