Photo: Swallowtail Garden Seeds / Public domain

Rex Begonia Care

Begonia rex · Begoniaceae

⚠️ Toxic to pets 🎯 Moderate ☀️ Medium, bright indirect 💧 Every 5–9 days

🕮 8 min read 🕓 Last reviewed: 2026-08-23

Care at a glance

Watering

Every 5–9 days

Light

Medium, bright indirect

Temperature

18–24 °C (64–75 °F)

Humidity

High

Soil

standard well-draining potting mix

Difficulty

Moderate

Mature size

25–45 cm (10–18 in)

Pet safety

Toxic to pets

Care effort High

The short version

A little attention keeps it happy.
Give it Medium, bright indirect.
Water every 5–9 days.
Keep away from cats and dogs.

The Rex Begonia (Begonia rex) is a popular houseplant from the Begoniaceae family, native to Tropical Asia. It is rated Moderate to grow and typically reaches 25–45 cm indoors. Here is everything you need to keep it healthy — watering, light, humidity, feeding, propagation, and pet safety. It is a Moderate grower, putting on most of its growth in the warm, bright months of spring and summer.

Also known asBegonia rexレックスベゴニア蟆叶秋海棠Bégonia rexKönigsbegonie

📋Quick facts

Growth rate	Moderate
Mature size	25–45 cm (10–18 in)
Native region	Tropical Asia
Plant family	Begoniaceae
Toxicity	Toxic
Air-purifying	No

⚖️Pros & cons

Pros

Compact — fits a desk or shelf

Cons

Toxic to cats and dogs
Needs high humidity to look its best

📷Photos

Rex Begonia — Begonia rex (4) — Cliff from Arlington, Virg / CC BY 2.0

💧Watering

Water your Rex Begonia roughly every 5–9 days, letting the top few centimetres of soil dry out between waterings. Always empty the saucer so the roots never sit in water — overwatering is the most common way this plant is lost.

Not sure when to water? Push a finger 2–3 cm into the soil and water only when it feels dry at that depth — a cheap moisture meter or the weight of the pot works too. Water thoroughly until it runs from the drainage holes, then tip away anything left in the saucer. Soft, yellowing lower leaves usually mean too much water; crispy, curling leaves usually mean too little. Always ease off in the darker months, when the plant drinks far less.

Never forget to water

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☀️Light & placement

Give your Rex Begonia medium to bright indirect light. It adapts to a range of spots but avoids harsh midday sun on the leaves.

An east-facing window is close to ideal, or a spot about a metre back from a brighter south- or west-facing window. Sheer curtains soften harsh afternoon sun. Rotate the pot a quarter-turn each week so it grows evenly toward the light.

🌡️Temperature & humidity

Keep it between 18–24 °C and away from cold draughts and heating vents. It prefers High humidity; if your air is dry, group it with other plants or use a humidifier.

🪴Soil & feeding

Plant it in standard well-draining potting mix. Feed with a diluted balanced feed monthly in spring and summer, and stop feeding in autumn and winter when growth slows.

🗓️Season-by-season care

Season	Watering	What to do
Spring (Mar–May)	Resume regular watering as growth restarts.	The main growing season begins — start feeding again, repot if it is pot-bound, and take cuttings now for the best success.
Summer (Jun–Aug)	This is the thirstiest season; check the soil more often.	Keep feeding on schedule, watch for pests in the warmth, and shield the leaves from scorching midday glass. Higher humidity is welcome.
Autumn (Sep–Nov)	Let the soil dry a little longer between waterings.	Taper off feeding as growth slows, and move the plant away from cold windows and doorways before the first chills.
Winter (Dec–Feb)	Water sparingly — overwatering now is the number-one killer.	Stop feeding, give it the brightest spot you have, and keep it away from radiators, heat vents, and cold draughts.

🪟Repotting

Repot roughly every 2 years, ideally in spring as growth picks up. Move up just one pot size (2–3 cm wider) with drainage holes — too big a pot holds water and invites root rot. Signs it is time: roots creeping from the drainage holes or circling the surface, water running straight through, or growth that has stalled. In the years you do not repot, scrape off and replace the top few centimetres of soil.

✂️How to propagate, step by step

Spring and early summer, during active growth, give the best success. Here is how to do it, step by step:

leaf cuttings

Take a healthy leaf (with a short piece of stalk where relevant) using a clean cut.
Let succulent leaves dry and callus for a day; skip this for soft-leaved plants.
Lay or press the leaf onto moist, gritty mix.
Keep it warm and lightly moist in bright, indirect light.
Over several weeks, tiny roots and plantlets appear — pot them on once they are established.

division at repotting

Water the plant the day before to reduce stress on the roots.
Slide it out of its pot and gently shake off the loose soil.
Tease the root ball into sections, each with healthy roots and a few shoots.
Pot each section into fresh mix at its original depth.
Water them in and keep out of direct sun for a week while they recover.

🔬Classification

Plant type	Foliage houseplant
Genus	Begonia
Family	Begoniaceae · Begoniaceae
Native to	Tropical Asia

🩺Common problems

Symptom	Likely cause	What to do
Brown, crispy tips	Dry air, or salts and fluoride from tap water	Raise humidity and water with filtered or rested water.
Brown spots on leaves	Inconsistent watering, cold draughts, or fungal issues	Water evenly, keep it warm, and remove badly affected leaves.

🩺 Plant Doctor →

🐛Pests & prevention

The usual indoor pests are spider mites (fine webbing, speckled leaves), mealybugs (white cotton-wool tufts), scale (small brown bumps), and fungus gnats (tiny flies from soggy soil). Inspect any new plant before it joins the others, wipe the leaves now and then, and let the topsoil dry to keep gnats away. At the first sign, isolate the plant, wipe or rinse off what you can, and treat with insecticidal soap or neem oil every week until it is clear.

🐾Is it safe for pets?

The Rex Begonia is toxic to cats and dogs (soluble calcium oxalates). Keep it out of reach of pets and children. If you think an animal has chewed it, contact your vet or a pet poison line. If a curious cat or dog chews it, soluble oxalates can, in larger amounts, bind calcium and affect the kidneys — so ingestion should be taken seriously. It is rarely life-threatening in small amounts, but rinse the animal’s mouth, take away any plant pieces, and call your vet if symptoms are severe or last more than a short while.

Toxicity information is a general guide based on ASPCA data. If your pet or child may have eaten any part of a plant, contact a vet or poison control right away.