Begonia is one of the largest genera of flowering plants, encompassing more than 2,000 species of perennial herbs and undershrubs in the family Begoniaceae (order Cucurbitales). The GBIF backbone taxonomy recognises approximately 3,101 species and infraspecific taxa. Plants range in stature from compact rosettes under a foot tall to the recently described Begonia giganticaulis, which can exceed 12 feet (3.6 m). Most cultivated varieties reach 8 inches to 2 feet.
Native to tropical and subtropical regions of Africa, Asia, and Central and South America — with Africa regarded as the centre of origin — begonias have diversified enormously across these biomes since their origins in the Paleogene to Miocene (roughly 20–65 million years ago). Most extant species likely arose during the Pleistocene.
The plants are monoecious: unisexual male and female flowers are borne separately on the same individual. Flowers appear in virtually every colour except blue — from white, yellow, and pale pink to deep red and orange — in single and double forms, and range in size from tiny blossoms to blooms the size of a dinner plate. Foliage is characteristically asymmetric at the base, often large and variously marked or variegated, in shades from bright green to bronze, burgundy, and silver-splashed.
Horticulturally, the genus is grouped into five broad categories: wax/semperflorens begonias (compact fibrous-rooted bedding plants), tuberous begonias (with large showy blooms), cane begonias (upright stems to 6 feet, typified by the polka-dot B. maculata), rhizomatous begonias (grown primarily for foliage, including the iron-cross B. masoniana), and rex begonias (a rhizomatous subgroup celebrated for extraordinarily colourful leaf patterns). One species, B. grandis, is notably cold-hardy, tolerating USDA hardiness zone 6.
Etymology
The genus name Begonia was coined by the French Franciscan monk and botanist Charles Plumier, who encountered six novel species in the Antilles during a late-seventeenth-century voyage. He named them in honour of Michel Bégon (1638–1710), a French colonial administrator who served as governor of Saint-Domingue (present-day Haiti) and was an enthusiastic patron of botany. The name first appeared in print in 1700 through Joseph Pitton de Tournefort's botanical writings. Carl Linnaeus formally adopted it in 1753, consolidating Plumier's six original species into a single type, Begonia obliqua, in Species Plantarum (vol. 2, p. 1056) — the foundational publication for modern botanical nomenclature.
Distribution
Begonias are distributed primarily across tropical and subtropical belts on three continents. In the Americas, they range from southern Mexico through Central America and across South America to Argentina, with documented occurrences in Bolivia, Brazil, Colombia, Ecuador, and Peru among others. The African range spans equatorial and southern Africa including Angola. Asian populations extend across South and Southeast Asia (Bangladesh, India, Philippines, Thailand) into southern China and Taiwan. Africa is regarded as the evolutionary centre of origin; the genus reached Asia via the Himalayan corridor approximately 15 million years ago during the mid-Miocene warm period, and colonised the Neotropics from African ancestors on at least two independent occasions. Some species have been introduced beyond their native ranges to Japan, Korea, Samoa, and the United States.
Taxonomy
Begonia L. (1753) is placed in the family Begoniaceae and order Cucurbitales, within the class Magnoliopsida (eudicots) and phylum Tracheophyta. With more than 2,000 accepted species, it ranks as one of the largest genera of flowering plants; the GBIF backbone recognises approximately 3,101 species and infraspecific taxa in total. The type species is Begonia obliqua L. Historical literature generated numerous synonymous genus names — including Augustia, Barya, and Cladomischus — all now subsumed under Begonia.
For horticultural and society purposes the American Begonia Society recognises nine cultivar groups: Cane-like, Shrub-like, Semperflorens, Rhizomatous, Rex, Tuberous, Hiemalis/Reiger/Elatior, Thick-stemmed, and Trailing/Scandent.
Ecology
Evolutionary divergence of Begonia is dated to the Paleogene–Miocene boundary (roughly 20–65 million years ago), with the majority of extant species diversifying during Pleistocene climatic fluctuations. Africa is the postulated centre of origin; the warm period of the mid-Miocene facilitated dispersal into Asia as the Himalayas reached their current elevations (~15 Ma), and subsequent long-distance dispersal from Africa to the Neotropics occurred independently at least twice.
In their native habitats begonias grow predominantly in humid, shaded environments — forest understoreys, stream banks, and rocky slopes — where they occupy terrestrial and sometimes epiphytic niches. Most species are adapted to moderate, stable warmth and cannot tolerate prolonged temperatures below 55°F (13°C). They thrive in well-drained substrates with high organic matter and require consistent moisture without waterlogging.
Cultivation
Begonias perform best in partial shade with a humid environment; full sun is tolerated by only a few species, and only in cool climates. A well-drained growing medium — moist but never saturated — with an acidic to neutral pH of 5.5–6.5 and high organic content suits most types. Plants are highly susceptible to root rot, so watering at the base (avoiding foliage) is recommended. Tall cane-type begonias may require staking, and all types benefit from shelter from strong wind as flowers and leaves are fragile.
Tuberous begonias undergo a seasonal dormancy; tubers should be lifted and stored in a cool, dry place over winter. Wax begonias (B. semperflorens hybrids) are widely grown as annual bedding plants outdoors and can persist as houseplants for four to five years. The hardy begonia (B. grandis) is the exception among the genus, tolerating temperatures down to USDA hardiness zone 6. Rex begonias need humidity above 75% to perform well.
Propagation
Most begonias are straightforward to propagate vegetatively. Stem cuttings and division are the most reliable methods across all groups. Rhizomatous and rex begonias can additionally be propagated from individual leaf cuttings or even sections of a single leaf — a small leaf section placed on damp growing medium will produce new plantlets at the cut veins. Seed propagation is also possible and is the standard method for commercial production of bedding semperflorens types; begonia seeds are extremely fine and require careful handling and light for germination.
Cultural Uses
Begonias hold cultural significance in several traditions. In China, the flower is a symbol of love and features prominently in classical literature and romantic poetry. In the Western language of flowers (floriography), begonias carry cautionary meanings: "a warning," "we are being watched," "this must end," or "take heed." The hybrid cultivar 'Kimjongilia', a tuberous begonia bred in Japan, was named in honour of North Korean leader Kim Jong-il and serves as an official floral emblem of North Korea, displayed at the annual Kimjongilia Festival in Pyongyang.
Most begonia species are edible in small quantities — the stems and flowers have a sour taste due to oxalic acid — but consumption in large amounts is hazardous. Oxalic acid in soluble calcium oxalate form can cause vomiting and salivation in pets and potential kidney failure in grazing animals; the roots are the most toxic part, and the sap can irritate skin.
