Rex Begonia Care: The Complete Guide to Growing Begonia Rex Indoors

Last updated: August 2026

Rex begonias need bright indirect light, evenly moist but never soggy soil, humidity above 50%, and warmth between 65-75°F. Water when the top inch of a chunky, peat-based mix dries, always from below the leaves, and feed weakly every two weeks in growth. Most problems trace back to wet soil, dry air, or cold drafts.

Rex begonias (Begonia rex-cultorum) are the most spectacularly patterned foliage plants you can grow on a windowsill. Silver spirals, black-and-pink starbursts, quilted purple ripples — no two cultivars look alike, and none of them look like anything else in a plant collection. They also have a reputation for being fussy, which is only half deserved. Rex begonias are not difficult, they are specific: they want particular things about water, air and soil, and once you give them those they grow steadily for years.

This guide covers everything from the exact soil mix we use in our greenhouse to diagnosing the three problems that kill most rex begonias indoors. If you are new to the genus as a whole, start with our broader begonia care guide, and browse the full genus in our begonia varieties identification guide.

What Makes a Rex Begonia Different

Begonias are divided into groups by growth habit, and that grouping tells you almost everything about care. Rex begonias are rhizomatous: they grow from a thick, knuckly, horizontal stem that creeps along the soil surface rather than from an upright cane or a fibrous crown. Leaves and roots both emerge from that rhizome.

Three practical consequences follow from that anatomy:

• They need wide, shallow pots. The rhizome spreads sideways. A deep pot holds a column of wet soil the roots never reach, and that is the single most common cause of rot.
• The rhizome must stay at the surface. Burying it invites rot. When repotting, set the rhizome so it sits half-exposed on top of the mix.
• They can rest. A rhizome stores energy, which is why a rex begonia can drop every leaf in winter and come back in spring. Cane types like our angel wing begonias do not do this.

Rex begonias were bred from Begonia rex, a species from northeast India, crossed with dozens of other Asian species. That heritage explains the care sheet: understory forest plant, warm year-round, high humidity, dappled light, thin leaf litter over fast-draining ground.

Light: Bright but Never Direct

Rex begonias want bright indirect light — roughly 200-500 foot-candles for 10-12 hours a day. In practical terms:

Exposure	Suitability	Notes
North window	Good	Ideal in summer; may be too dim Nov-Feb in northern states
East window	Best	Gentle morning sun, bright the rest of the day
West window, 2-3 ft back	Good	Sheer curtain needed for the late afternoon
South window, direct	Poor	Bleaches and scorches patterned leaves within days
LED grow light	Excellent	12-14 in above the plant, 12 hr timer

Colour is your feedback loop. Deep silvers and reds intensify in good light and fade toward flat green in low light. Leaves that look bleached, papery or bronzed are getting too much. Leaves that stretch on long petioles toward the window and sit widely spaced are getting too little. If your windows cannot deliver, a grow light works beautifully — see our comparison of LED, fluorescent and full-spectrum grow lights.

Watering: The Skill That Decides Everything

Rex begonias want soil that is evenly moist, never wet, never bone dry. That is a narrower window than a pothos tolerates, and it is where most plants are lost.

The method

1. Check the top inch with a finger or a wooden skewer. Water only when it reads dry.
2. Pour slowly at the soil surface, on the opposite side from the rhizome crown, until water runs from the drainage hole.
3. Empty the saucer within ten minutes. Rex begonias must never stand in water.
4. Keep water off the leaves. Wet foliage plus still air equals powdery mildew and bacterial leaf spot.

Indoors that typically means every 5-10 days in summer and every 10-18 days in winter, but the interval is an outcome, not a rule. Bottom watering is a reasonable alternative and keeps foliage dry — set the pot in an inch of water for 10-15 minutes, then remove it.

Overwatering symptoms are mushy stems at the rhizome, yellowing lower leaves and a sour soil smell. Underwatering shows as sudden wilting with dry, curling leaf margins. If you struggle to tell them apart, our guide on overwatered vs underwatered plants walks through the differences, and if the rhizome has already gone soft, read root rot treatment immediately — rex begonias decline fast once rot starts.

Humidity and Air: The Non-Negotiable

Rex begonia leaves are thin, large and hairless in most cultivars, which means they lose moisture fast. Target 50-60% relative humidity. Below 40% you will get crispy edges no matter how well you water, because the problem is atmospheric, not in the pot.

What actually works, in order of effectiveness: a small ultrasonic humidifier near the plant; grouping several plants together; a cabinet or glass-fronted shelf; a bathroom with a window. What does not work: misting the leaves (brief, and it invites mildew) or a pebble tray (raises humidity by a couple of points at best). Our humidity guide covers the measurements behind those claims.

The complication is that rex begonias want humid air but not stagnant air. Humid and still is exactly the condition powdery mildew needs. A small clip fan on low, aimed past rather than at the plant, solves it. This is why rex begonias often struggle in sealed terrariums but thrive in a humid room with a fan.

Soil, Pots and Repotting

Rex begonias need a mix that holds moisture but drains within seconds. A standard bag of potting soil is too dense. Our greenhouse mix:

• 2 parts peat- or coir-based potting mix
• 1 part perlite or pumice
• 1 part fine orchid bark or coarse coco chips
• A handful of horticultural charcoal

Use shallow, wide pots — a 6-inch azalea pot or bulb pan beats a 6-inch standard pot. Terracotta is a real advantage here because it wicks moisture from the sides and shortens the wet period after watering; see terracotta vs plastic pots for the trade-offs. Whatever you choose, it must have a drainage hole.

Repot every 12-18 months in spring, going up only one pot size. Rex begonias resent being overpotted. Set the rhizome half-exposed at the surface and firm the mix gently rather than packing it. If you are unsure whether it is time, check the signs of a root-bound plant, and follow the general repotting walkthrough for technique.

Feeding

Feed a balanced liquid fertilizer at quarter to half strength every two weeks from March through September, then stop entirely for the winter rest. Rex begonias are light feeders and their fine surface roots burn easily. A 20-20-20 or a 3-1-2 ratio both work; higher-nitrogen formulas produce larger but flimsier leaves with weaker colour.

Flush the pot with plain water every third or fourth feeding to clear accumulated salts, which otherwise show up as a white crust on the soil and brown leaf tips that look exactly like a humidity problem. Full details on ratios and timing are in our indoor plant fertilizer guide.

Temperature and Winter Dormancy

Keep rex begonias between 65-75°F during the day and above 60°F at night. They tolerate a little cooler, but below 55°F growth stops and leaf drop begins. They hate drafts specifically — an open winter window, an air-conditioning vent or a door to a cold garage will strip leaves in a week.

Expect a genuine seasonal slowdown. As days shorten, many cultivars drop half or all of their leaves and look dead. Do not throw the plant away and do not try to water it back into growth. Instead:

• Cut watering back to barely moist, roughly monthly
• Stop fertilizing completely
• Keep the rhizome warm and out of drafts
• Leave it in the same pot

New leaves usually push in February or March. Resume normal watering and feeding once you see them. Our winter houseplant care guide covers the seasonal shift across a whole collection.

Popular Rex Begonia Cultivars

Cultivar	Look	Difficulty
'Escargot'	Spiralled snail-shell leaves, silver and olive	Moderate; largest leaves, most humidity-sensitive
'Fireworks'	Silver leaves with purple-black centres and margins	Easy for a rex
'Jurassic' series	Big ruffled leaves, many colourways	Easy; bred for vigour
'Red Kiss'	Deep burgundy with a black star centre	Moderate
'Silver Limbo'	Compact, pewter-silver, small leaves	Easiest; small leaves lose less water
'Harmony's Red Robin'	Puckered scarlet-and-bronze	Moderate

If you want the look with fewer requirements, start with a small-leaved cultivar like 'Silver Limbo' — leaf size correlates strongly with humidity fussiness.

Propagating Rex Begonias

Rex begonias are among the easiest houseplants to multiply, and leaf propagation is genuinely reliable.

Leaf-vein cuttings (highest yield)

1. Take a healthy mature leaf with a short stub of petiole.
2. Turn it upside down and slice cleanly across each main vein, about an inch from the centre.
3. Lay it face-up on moist, sterile mix and pin it flat with hairpins or small stones so every cut touches soil.
4. Cover with a clear dome or bag; keep at 70-75°F in bright indirect light.
5. Vent briefly every couple of days. Plantlets emerge from the cuts in three to six weeks.

Wedge cuttings

Cut the leaf into pie-shaped wedges, each containing a main vein, and insert the pointed end an inch into moist mix. Slightly slower but easier to manage in small pots.

Rhizome division

At repotting, cut the rhizome into 2-inch sections, each with at least one growth point, and lay them on moist mix. Fastest route to a full-size plant. Our general houseplant propagation guide covers the sterile technique that keeps rot out of any of these methods.

Troubleshooting Rex Begonia Problems

Symptom	Likely cause	Fix
Crispy brown leaf edges	Humidity under 40%, or salt buildup	Humidifier to 50-60%; flush pot with plain water
White powdery patches	Powdery mildew (humid + still air)	Remove leaves, add airflow, potassium bicarbonate spray weekly
Mushy rhizome, sour smell	Overwatering / rot	Unpot, cut to clean tissue, repot shallow in fresh airy mix
Sudden total leaf drop, autumn/winter	Normal dormancy	Reduce water, stop feeding, keep warm, wait for spring
Sudden leaf drop, any season	Cold draft or temperature swing	Move away from vents, doors and single-pane glass
Faded, flat green colour	Too little light	Move to an east window or add a grow light
Bleached, papery patches	Direct sun scorch	Filter with a sheer curtain or pull back 2-3 ft
Fine webbing, stippled leaves	Spider mites (dry air)	Raise humidity, rinse, treat with insecticidal soap
Tiny black flies over soil	Fungus gnats in wet mix	Let top inch dry; see the gnat guide below
Leggy stretched petioles	Insufficient light	Increase light; prune leggy growth in spring

Rex begonias attract the usual indoor pests, with spider mites and mealybugs the most common. Because the leaves are thin and often hairy, always test any spray on one leaf first. Use our visual pest identification guide to confirm what you are dealing with, and the fungus gnat guide if the problem is in the soil rather than on the leaves. If a plant is already far gone, our plant revival walkthrough gives you a triage order.

Should You Let It Flower?

Rex begonias produce small pink or white flowers on wiry stems, usually in late winter or spring. They are unremarkable, and flowering diverts energy from the foliage you actually bought the plant for. Most growers pinch the flower stems out as soon as they appear. It is a preference, not a rule.

A Note for Pet Owners

Rex begonias are toxic to cats and dogs. The rhizome carries the highest concentration of soluble calcium oxalates, and chewed leaves cause mouth irritation, drooling and vomiting. If pets have run of the house, keep rex begonias on high shelves or choose from our pet-friendly houseplant collection instead — our roundup of 20 non-toxic plants for cats has patterned alternatives worth considering.

Where to Buy a Healthy Rex Begonia

Inspect the rhizome, not the leaves, when buying. It should be firm and pale, sitting on the soil surface with no soft brown spots. Check leaf undersides for mites and the soil for gnats. Avoid plants in deep pots of dense black soil — they are usually already halfway to rot.

Rex begonias ship well in spring and autumn but sulk in extreme heat or freezing weather, so buy from a grower who holds shipments during weather events. We grow, propagate and pack our own stock; browse our easy-care statement foliage, our new arrivals, or best sellers. If you are ordering live plants online for the first time, our plant shipping guide explains what to expect on arrival.

Quick Reference Care Card

Factor	Rex begonia requirement
Light	Bright indirect; east window ideal; no direct sun
Water	When top inch dries; never soggy; keep leaves dry
Humidity	50-60% with gentle air movement
Temperature	65-75°F day, above 60°F night, no drafts
Soil	Chunky peat/coir mix with perlite and bark
Pot	Wide and shallow, drainage hole, terracotta preferred
Fertilizer	Quarter to half strength, every 2 weeks, spring-autumn only
Dormancy	Partial or full leaf drop in winter is normal
Toxicity	Toxic to cats and dogs
Propagation	Leaf-vein cuttings, wedges, or rhizome division

Frequently Asked Questions

Are rex begonias hard to care for?

Rex begonias are moderately demanding rather than difficult. They fail for three predictable reasons: soggy soil, dry indoor air, and cold drafts. Solve those with a chunky airy mix, watering only when the top inch dries, and 50-60% humidity, and a rex begonia is no harder than a calathea.

Why are my rex begonia leaves getting crispy brown edges?

Crispy edges are almost always low humidity, sometimes combined with underwatering or fertilizer salt buildup. Rex begonias want 50-60% relative humidity; below about 40% the thin leaf margins dry faster than the plant can replace the moisture. Group plants, add a humidifier, and flush the pot every few months.

How often should I water a rex begonia?

Water when the top inch of soil feels dry, which is usually every 5-10 days indoors depending on pot size, light and season. Never water on a fixed schedule. Rex begonias have shallow rhizomes that rot quickly, so pour slowly at the soil surface and empty the saucer within ten minutes.

Do rex begonias go dormant in winter?

Many rex begonias slow dramatically or die back partially in winter, dropping leaves and looking half dead. This is normal dormancy triggered by short days and cool temperatures. Reduce watering to barely moist, stop fertilizing, keep the rhizome above 60°F, and new leaves usually appear by early spring.

Are rex begonias toxic to cats and dogs?

Yes, rex begonias are considered toxic to cats and dogs. The tubers and rhizomes contain the highest concentration of soluble calcium oxalates, which irritate the mouth and throat and can cause vomiting. Keep them on high shelves in pet homes, or choose a genuinely pet-safe houseplant instead.

Can you propagate rex begonia from a single leaf?

Yes. Rex begonias root readily from leaf cuttings, and a single mature leaf can produce several plantlets. Slice through the main veins on the underside, pin the leaf flat onto moist mix, and keep it covered at 70-75°F. Plantlets typically emerge from the cut veins in three to six weeks.

Why does my rex begonia have white powder on its leaves?

White dusty patches are powdery mildew, the most common rex begonia disease. It thrives in humid air with poor circulation and cool nights. Remove affected leaves, run a small fan for airflow, avoid wetting the foliage, and treat remaining growth with a potassium bicarbonate or neem-based spray weekly.

How big do rex begonias get indoors?

Most rex begonia cultivars stay compact indoors, reaching 8-14 inches tall and about as wide, with individual leaves 3-8 inches across. Larger cultivars such as 'Escargot' can spread to 18 inches. They grow from a spreading rhizome, so wide shallow pots suit them better than deep ones.

Written and reviewed by Robert, Founder of Divine Roots — he grows, propagates and ships the plants we sell, and the care advice here reflects what actually works in our own greenhouse.