Begonia Rex

How to care for Begonia Rex

Light

Rex begonias need bright, indirect light to maintain the intensity of their leaf colouration. An east- or north-facing windowsill is often suitable; a west-facing position can work if the plant is shaded from the hottest afternoon sun. Direct sunlight will scorch the delicate leaves, causing bleached or brown patches, whereas insufficient light leads to dull, faded patterns and weak, elongated growth. Artificial grow lights on a 12-14 hour cycle can supplement low winter light effectively.

Watering

Allow the top centimetre of compost to dry out before watering again, then water thoroughly until it drains from the base. Empty the saucer after 30 minutes to prevent root rot, to which rex begonias are particularly susceptible. Reduce watering frequency in autumn and winter when growth slows. Always use tepid, ideally filtered or rain water, as these plants can be sensitive to the fluoride and chlorine present in tap water.

Soil and potting

A light, well-aerated, free-draining compost is essential. A suitable mix combines a good-quality peat-free houseplant compost with 20-30% perlite or coarse horticultural grit to improve drainage and aeration around the roots. Avoid heavy, moisture-retentive composts; rex begonias do not tolerate waterlogged roots and will decline rapidly in compacted or dense media.

Feeding

Feed every two to four weeks throughout the active growing season (spring and summer) using a balanced, water-soluble fertiliser diluted to half the recommended strength. Excessive nitrogen encourages leafy growth at the expense of colour intensity, so some growers prefer a fertiliser lower in nitrogen or alternate with one higher in potassium. Cease feeding entirely in autumn and winter when the plant is resting.

Humidity and temperature

Rex begonias prefer relatively high humidity of 50-70%, which reflects their subtropical forest origins. Stand pots on a tray of moist expanded clay pebbles, use a humidifier nearby, or group plants together to raise ambient moisture. Avoid misting directly onto the leaves, as water sitting on the foliage promotes fungal diseases such as powdery mildew. Maintain temperatures between 18 and 24 C and protect plants from cold draughts, air-conditioning units, and temperatures below 13 C.

Repotting

Repot in spring when roots begin to emerge from the drainage holes or the plant appears to be pushing itself out of the pot. Choose a container only one size larger, as rex begonias perform better when slightly root-bound and an overly large pot holds excess moisture. Shallow, wide pots (azalea or half pots) suit their shallow root systems well. Refresh the compost annually even if a full repot is not required.

Pruning

Remove any dead, damaged, or dying leaves promptly at the base of their stalks to maintain hygiene and airflow. Leggy stems can be cut back to a healthy node to encourage bushier growth. Spent flower spikes are best removed as soon as they fade; many growers remove flower buds as they appear to direct energy into the foliage. General shaping can be carried out in early spring before growth resumes fully.

Is Begonia Rex toxic?

Common problems

How to propagate

Leaf-petiole cuttings

Remove a healthy leaf with 3-5 cm of its petiole (leaf stalk) intact. Insert the petiole at an angle into moist, free-draining propagation mix, place in a warm, humid environment (ideally around 21 C), and small plantlets should emerge from the base of the petiole within 4-8 weeks.

Leaf-section cuttings

Cut a mature leaf into sections roughly 4-5 cm square, ensuring each section contains at least one prominent vein. Lay sections flat on moist propagation mix or insert them vertically to a depth of about 1 cm; roots and plantlets develop from the cut veins over several weeks when kept warm and humid.

Division

When repotting a mature, multi-stemmed plant, gently separate the root ball into two or more sections, each with healthy roots and at least one growing point, and pot each division individually into fresh compost.

Where Begonia Rex comes from

Native to Assam, north-eastern India.

Story and origins

The genus name Begonia honours Michel Begon (1638-1710), a French politician and enthusiastic patron of botany who served as Governor of Saint-Domingue (now Haiti) and encouraged botanical exploration in the Caribbean. The species epithet rex is Latin for 'king', a reference to the plant's regal and imposing foliage, which was considered extraordinarily ornamental when first described. The cultivar group name rex-cultorum means, broadly, 'the king begonias of cultivation', distinguishing the hybrid group from the wild species and acknowledging their complex cultivated origin.

Begonia rex was first described scientifically in 1857 from a specimen collected in the Assam region of north-eastern India, though it is believed that plants had already been reaching European nurseries in the preceding years. Its introduction to British and Continental horticulture coincided with the height of the Victorian enthusiasm for exotic foliage plants, sometimes called 'foliage fever'. Hybridisers, particularly in Britain, Belgium, and France, rapidly crossed B. rex with various tuberous and rhizomatous begonia species, producing an enormous array of cultivars that became fashionable conservatory and greenhouse plants throughout the late nineteenth century. The group's popularity briefly declined in the early twentieth century but was revived in the latter half of the century as houseplant culture expanded, and rex begonias are now among the most widely sold ornamental foliage houseplants globally.

Varieties to know

Begonia 'Escargot'

Distinctive spiralling silver and green leaves with a snail-shell pattern; one of the most recognisable and widely sold cultivars

Begonia 'Fireworks'

Deep purple-black leaves with bright silver spots and pink margins; bold contrast makes it a popular choice

Begonia 'Red Robin'

Deep red to burgundy leaves with a metallic sheen; reliable and relatively compact grower

Begonia 'Stained Glass'

Silver leaves with a translucent quality, dark green veining, and purple-red undersides, resembling a stained glass window

Begonia 'Merry Christmas'

Red and green variegated leaves edged with silver; the festive colour combination made it a classic cultivar in the trade

Fun facts

• Rex begonias can exhibit iridescence in their leaves as a result of specialised cells called iridoplasts that reflect blue-green light, an adaptation believed to help the plant capture more light in dim forest understoreys.
• The wild species Begonia rex was introduced to cultivation in Europe in the 1850s after being discovered in Assam; Victorian hybridisers quickly began crossing it with other species, and the rex-cultorum group now encompasses thousands of registered cultivars.
• Rex begonias are among the few houseplants that are propagated commercially almost entirely by vegetative methods, as their seeds are extremely small (almost dust-like) and difficult to germinate reliably outside specialist conditions.
• Unlike many begonias, the rex-cultorum hybrids tend not to produce a significant tuber; they grow from a rhizome (a creeping stem at or just below the soil surface), which influences both their shallow root system and their propagation requirements.
• The shimmering metallic appearance of many rex begonia leaf surfaces is caused by air pockets between the upper layers of leaf cells, which scatter and reflect light rather than simply absorbing it.

Begonia Rex FAQ