Begonia rigidifolia

**Quick Species Info**
Species	rigidifolia
Region	Southeast Asia
Country	Vietnam
Year published	(Year Published)
Date of Origin	2011
Plant Type	Rhimatous
Section	Begonia
Chr 2n	(Count)

Begonia rigidifolia

Species Information

Classification

Begonia rigidifolia belongs to the Begonia section. It is a lithophytic rosulate herb.

Distribution

This begonia species is native to central Vietnam, specifically found in Quang Binh province, Tuyen Hoa district, Lam Hoa municipality, and Chuoi village.

Habitat

Begonia rigidifolia thrives in primary broad-leaved evergreen dry forests on very steep slopes and on tops of rocky ridges composed of highly eroded crystalline limestone at elevations ranging from 200 to 250 meters above sea level. It grows as a lithophytic herb on shady vertical cliffs.

Characteristics

- Rhizome: Plagiotropic, creeping, fleshy, stout, (3)4–5(7) cm long, (0.5)0.8–1(1.2) cm in diameter, densely covered by dark brown persistent, long, densely hairy bracts. - Stipules: Persistent, herbaceous, purple (brown when dry), oblong-ovate to narrowly ovate, (0.7)1–2(2.5) cm long, (3)4–6(8) mm wide, with revolute lateral margin, caudate, keeled, and hairy outside by sparse long white hairs, attenuate into long hairy filiform-caudate mucro 7–10(12) mm long. - Leaves: Petiolate, peltate, symmetric to slightly asymmetric, ovate, almost entire or irregularly, indistinctly, finely denticulate along the margin, attenuate at apex, with radiate venation of 6 slightly branching veins, (5)7–12(15) cm long, (4.5)5–9(11) cm wide, glabrous, coriaceous, leathery, rigid; brightly emerald-green with irregular radiantly arranged dirty-brownish or dark green to almost black-green spots above, light greenish-white to almost pure white, with irregular areas flushed by scarlet-purple below.

Flower Details

- Inflorescence: Axillary, erect or ascending from the apical part of the rhizome, peduncle straight, purple, glabrous, (6)8–14(18) cm long, as long as leaves or nearly so, bearing very short dichotomously branching bracteate, many flowered cyme 1–2(4) cm long with staminate and pistillate flowers. - Flowers: Pedicellate, monosexual; sepals white, pink–purple toward apical margin; petals pure white.

 - Staminate flowers: Zygomorphic, dichlamydeous, normally with 2 opposite broadly ovate to almost orbicular sepals (6)7–11(14) mm across and 2(4) opposite narrowly obovate to broadly oblanceolate petals (4)5–9(11) mm long, (1.5)2–3.5(4) mm wide; stamens numerous, in a dense cluster, brightly yellow, arranged in numerous whorls on a short conical axis, filaments free, (0.8)1–1.4(1.6) mm long, anthers narrowly obovoid, as long as filaments, slightly retuse at apex.
 - Pistillate flowers: Zygomorphic, dichlamydeous, normally with 2 sepals and 1 petal; sepals subopposite, broadly ovate to reniform, orbicular at apex, broader than long, (3)7–8(9) mm long, (4)9–11(13) mm wide; petal narrowly obovate to broadly oblanceolate, (3)5–6(7) mm long, (1.5)2.5–3(3.5) mm wide, roundish at apex; styles 3, (2)2.5(3) mm tall, brightly yellow, connate at the base into a short common stalk, styles broadening and flattened toward the apex, stigmas densely setose-papillose, linear-cristate, lateral sides expanded into a short helicoid band.
 - Ovary: Inferior, composed of 3 carpels, densely shortly papillose, 3-angular, with low lunate to oblique-triangular wings along each edge; apical wing distinctly larger; placentae axial, bilamellate.

Etymology

The species name "rigidifolia" is derived from its characteristically rigid coriaceous leaves, which are unusual among related species.

Ecology

Begonia rigidifolia primarily inhabits primary broad-leaved evergreen dry forests on remnant hills composed of solid, highly eroded rocky crystalline limestone at elevations ranging from 200 to 300 meters above sea level. It grows in crevices of vertical shady cliffs in the middle and upper parts of remnant karstic hill slopes. It typically flowers in April to May (June) and fruits in July to August (September). This species is not common and usually forms small populations, making it vulnerable (VU).

Notes

Begonia rigidifolia is easily recognized by its relatively stout fleshy peltate leaves and has an obvious relation to related species such as B. cavaleriei H. Lév., B. peltatifolia Li, B. pulvinifera C.-I Peng et Yan Liu, B. vietnamensis H.Q. Nguyen et C.-I Peng, B. wangii T.T. Yu, B. ignorata Irmsch., B. kingiana Irmsch., and B. tigrina Kiew. It can be distinguished by its large stipules covered outside with numerous large white hairs, long-ciliate petioles, rigid coriaceous glabrous emerald-green leaves marked above with black-green and below with scarlet irregular spots, as well as staminate flowers with 4 tepals and pistillate flowers of 3 tepals.

References

- List of sources and references used to describe Begonia rigidifolia.

Care

Caring for Begonia rigidifolia in cultivation should aim to replicate its natural habitat conditions