The genus Begonia, belonging to the plant family Begoniaceae, is an exceptionally large and diverse group of flowering plants highly prized for their ornamental qualities. With over 2,000 different species identified, begonias are found throughout tropical and subtropical regions worldwide. This vast array means begonias do not have a single, uniform appearance; instead, they display an incredible range of foliage, flower characteristics, and growth structures. Understanding their morphology requires looking closely at the distinct features of their leaves, flowers, and underground structures.
Defining Features of Begonia Leaves
Begonia foliage is often the most visually striking part of the plant, exhibiting a diversity of shapes, colors, and textures. A characteristic feature found across most species is the leaf’s asymmetry, meaning one side of the blade is noticeably larger than the other. This uneven shape contributes to their unique silhouette.
The color and pattern variation is extensive, ranging from deep emerald green to bronze, maroon, black, and silver. Many varieties display complex variegation, appearing as silvery spots, spirals, or distinct zones of color along the veins. The backs of the leaves can also be highly decorative, sometimes showing colors like deep red or burnt orange.
Leaf surfaces vary dramatically in texture, from smooth and waxy to fuzzy, hairy, or puckered. These textures are often created by fine hairs, known as trichomes, which can give the foliage a metallic sheen or a felted appearance. This combination of shape, color, and texture makes the leaves the primary reason many types are cultivated as foliage plants.
Flower Structure and Appearance
Begonias produce monoecious flowers, meaning the individual male and female flowers are separate but develop on the same plant. The male flowers are typically the more noticeable, showier blooms, often featuring numerous prominent stamens in the center. These male flowers generally have two pairs of petal-like structures, with two larger ones often enclosing two smaller ones.
The female flowers are distinguished by the presence of an inferior ovary situated beneath the petals. This ovary is often triangular or prominently winged, a feature that becomes more noticeable as it develops into a winged seed capsule. Female flowers also contain two to four branched or twisted stigmas in their center.
The colors of the flowers span a wide spectrum, including white, pink, various shades of red, yellow, and orange, though true blue is absent. Flower size varies greatly, from small, simple clusters to large, spectacular double blooms that resemble roses or camellias, especially in hybrid tuberous types. In tuberous begonias, the male flowers are often intentionally bred to be large and double, while the female flowers are smaller.
The Three Main Growth Habits
The overall visual presentation of a begonia is dictated by its underground structure, which determines its growth habit. Begonias are classified into three main groups: cane-like, rhizomatous, and tuberous.
Cane-Like Begonias
Cane-like begonias are characterized by their upright, often tall stems that have clearly defined, bamboo-like nodes. This structure leads to a generally sparse, airy appearance, with foliage often clustered near the top of the stems. The ‘Angel Wing’ begonia is a well-known example of this type.
Rhizomatous Begonias
Rhizomatous begonias grow from a thick, creeping stem, or rhizome, that typically rests on or just below the soil surface. This structure encourages a dense, mounding growth habit, leading to a full, bushy appearance. The leaves of this group, which include the ‘Rex’ begonia types, often grow quite large and are the primary focus of their ornamental appeal, with the rhizome storing resources for the plant.
Tuberous Begonias
Tuberous begonias grow from a rounded, dormant underground tuber, which allows them to produce some of the largest and most flamboyant flowers in the genus. These types can have either an upright, compact form or a trailing habit, making them popular for hanging baskets. The large, double flowers are the main visual draw, and the plant’s growth cycle is tied to the tuber, which requires a period of dormancy.