Rex Begonia

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Plenty of light but no direct sun, which can scorch its thin, patterned leaves. Medium light farther into the room works too, though growth likely slows.

Wild Begonia rex grows in rocky, forested valleys and on slopes from the eastern Himalaya into Myanmar (Missouri Botanical Garden; Kew), under trees rather than out in the open. Outdoors, the Garden rates rex begonias for part shade to full shade.

Sun landing on the leaf is the threat to all that silver and plum, so choose the window to shield it. An east-facing sill behind a sheer curtain is likely a good fit, as is an unobstructed north-facing window. With south or west windows, keep it several feet from the glass, where light fills the space but the rays fall short.

Mind the cold too. NC State notes begonias don’t tolerate temperatures below 55°F, and a window in January can run colder than the air around it, so in deep winter give the pane a little room.

Bright and shaded, those leaves hold their depth of color.

About every 5-7 days in summer and 7-10 in winter, keeping the soil lightly damp, not soggy; water the soil, not the leaves, and skip the mister. Its rhizome creeps along the soil’s face, so a wet pot can rot it.

Here’s its contradiction: it loves humid air and dislikes wet leaves. NC State puts its humidity needs above 75% and calls rex begonias excellent terrarium plants, while Missouri Botanical Garden sets the bar above 50%, with some varieties wanting more. NC State suggests bathrooms and kitchens as good spots.

So retire the spray bottle. NC State advises against misting to prevent disease, since botrytis and powdery mildew can take hold on the foliage; moving air helps keep both away.

Radiator season is when it shows the strain: leaf edges that brown and crisp, and patterns that lose their gloss. If that bothers you, give it a season in the bathroom or a terrarium; it can limp through a winter either way, though it looks its best in the steam.

Gone for a while? A week is about its limit, so water it the day you leave.

Broad leaves fan off a creeping rhizome in a mound 12-18 inches high, for a side table, shelf, or terrarium. Keep it at or below eye level; the leaves turn toward the light, so turn the pot to face the pattern your way.

That rhizome is a thickened stem (UConn Extension), so the clump widens more than it climbs; Missouri Botanical Garden recommends a shallow pot to match.

Leaves on the wild species can reach a foot long and 8 inches across (Missouri Botanical Garden), which is how a plant barely a foot tall can spread its leaves well past the rim of its pot.

Every named variety you buy is a clone. Rex begonias root from leaf cuttings (Penn State Extension), and those cuttings come true to the parent, so a patented cultivar is copied leaf by leaf, exactly as its breeder found it (US plant patents).

A chewed leaf may make a dog or cat drool or vomit, and that usually passes; the ASPCA lists it as toxic to both. For kids, CHOP lists begonias as non-poisonous, though the sap can irritate skin.

Most of its irritant sits in the roots, so a pet digging in the pot is more of a worry than one nibbling a leaf.

Begonias carry soluble calcium oxalates (ASPCA), which explains the drool and the upset stomach. The ASPCA links them to kidney failure in grazing animals that eat a great deal. For a pet that only nibbles, the signs it lists stop at drooling and vomiting.

For kids, the news is good. CHOP and Poison Control list begonias as non-poisonous, so a curious bite is nothing harmful. The sap can irritate skin, and a quick hand wash after pruning or repotting takes care of it.

If a pet’s stomach doesn’t settle or anything worries you, call your vet or the ASPCA Animal Poison Control Center (a fee may apply). For a child, Poison Control can help.

A rex begonia stays low, so a high shelf or a plant stand lifts its leaves above nose height. A dog that digs, or a cat that treats potting soil like a litter box, gets past the leaves to the rhizome. A pot cover or a room they rarely visit keeps paws out of the soil.

1. ASPCA: mild for dogs (rates the whole genus).
2. ASPCA: mild for cats (rates the whole genus).
3. CHOP: safe for kids.

Dogs: Only the ASPCA rates it for dogs, and the signs it lists are mild.

Cats: Only the ASPCA rates it for cats, and the signs it lists are mild.

Kids: CHOP and Poison Control list it as non-poisonous. Care note: oxalate in the plant may irritate skin (not confirmed by CHOP or Poison Control).

Warm, humid rooms suit it: 63-80°F, not below 60°F, and away from cold winter glass. It likes 75-90% humidity, and dry air crisps the leaf edges.

Temperature

63-80°F

Humidity

75-90%

Mealybugs are the common guest: check the leaf axils, the base of the leaf stalks, and the undersides. Spider mites, whiteflies, and thrips are occasional; scale sits on stems and stalks. Mites favor hot, dry air.

• Mealybugs
• Spider mites
• Thrips
• Whiteflies
• Scales

Mildew and rot are the bigger worries; bugs turn up now and then.

Powdery mildew shows as white, dusty patches on the leaves. Pick off the worst leaves, give it more air around it, and keep water off the leaves; NC State Extension’s advice is good circulation and clearing away dead leaves.

Botrytis, a gray, fuzzy mold on leaves and stalks, and stem rot, soft dark stalks at the soil line, both come from damp, still conditions. Remove the affected parts, let the soil dry slightly before the next watering, and never let it sit in a wet saucer.

Mealybugs look like tufts of white cotton where the leaves meet the stalks: dab them with a cotton swab dipped in rubbing alcohol. Whiteflies and spider mites hide under the leaves; an insecticidal soap spray, aimed at the undersides, takes care of both.

Remove dead or mildewed leaves all year, and feed at quarter strength every 2-3 weeks in spring and summer, stopping in October. Each spring, repot once the rhizomes reach the pot sides, dividing every few years.

• Feed10× a year
• Clean leaves12× a year
• Repot1× a year
• Divide1× a year

A rich potting mix that drains fast, in a pot with a drainage hole and not too big, since extra soil stays wet.

Repot in spring, once the roots circle the pot, one size up; Clemson Extension says that’s also the time to divide a crowded plant.

A balanced liquid fertilizer at half strength every other watering while it’s growing (Clemson’s rule), and none in winter.

Each broad leaf is painted in its own swirl of silver, plum, and pink, so no two look alike. The surface is glossy and deeply textured, and the leaves overlap to cover the soil completely.