Rex begonia (painted-leaf begonia) care

Light

Rex begonia thrives in bright indirect light — the conditions just back from a sunny window, with plenty of ambient brightness but rarely any direct rays on the leaves themselves. Bright indirect light. Direct sun bleaches the colour patterns out of the leaves. If you are not sure whether your spot is bright enough, a free phone lux-meter app at midday is the quickest way to check; aim for 800-1,500 lux.

Watering

Water rex begonia when the top 1-2 cm of soil is dry, every 5-7 days. The actual day count varies with pot size, light level, and the season — the finger test (or, better, lifting the pot to feel its weight) is more reliable than a calendar. Empty any drainage saucer after watering so the pot is never sitting in water. Water from the side of the pot, never onto the foliage. Soggy crowns are a common cause of rot.

Soil and pot

Rex begonia grows best in light, peat-free potting mix with perlite. A light moisture-retentive mix with 20-30% perlite. Rhizomatous rex roots are shallow, so wide shallow pots suit them. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Rex begonia sits happiest at around 50-70% humidity and 16-24°C (60-75°F). High humidity keeps the foliage glossy; under 40% leaves crisp at the edges. If you keep the room above 16 year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed rex begonia sparingly. Quarter-strength balanced feed every 3-4 weeks during the growing season. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on rex begonia in the Growli community. Each is annotated with the most common cause so you know where to start.

• Crispy leaf edges — Low humidity or direct sun.
• Mushy stems — Crown rot from water on the rhizome; let the surface dry between waterings.
• Powdery mildew — Improve air movement and avoid wetting the leaves.
• Faded colours — Either too much direct sun or too little light overall.

Propagation

Leaf cuttings — slice a healthy leaf across the veins and lay it on moist mix under a humidity dome. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Rex begonia is toxic to pets. ASPCA lists Begonia species as toxic to cats and dogs due to soluble calcium oxalates. Most-toxic part is the underground rhizome. Symptoms include vomiting and mouth irritation. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Rex begonia deep-dive guides

Every aspect of rex begonia care, each with its own calibrated guide:

• Rex begonia watering schedule
• Rex begonia light requirements
• Best soil mix for rex begonia
• Rex begonia fertilizing guide
• When to repot rex begonia
• How to propagate rex begonia
• Rex begonia growth rate & size
• Rex begonia cold hardiness
• Rex begonia temperature & humidity
• Is rex begonia toxic to cats & dogs?

Related guides

Rex begonia is also commonly called painted-leaf begonia or king begonia.

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• All 200 plant care guides in the Growli library