Bauhinia purpurea
(purple bauhinia)

B. purpurea is a fast-growing tree that has a wide natural distribution range and has been introduced worldwide. This species has escaped from cultivation and has successfully established in a wide variety of habitats (Connor, 2001; PIER 2015). Once established, it grows displacing native vegetation (Oviedo Prieto et al., 2012). In this species, seeds form very rapidly and mature trees may show numerous pods (Orwa et al., 2009). Additionally, high germination rates (~ 99%) have been recorded for this species when seeds were placed in moist conditions (Connor, 2001). Currently, B. purpurea is listed as invasive in Cuba, Fiji, New Caledonia and Western Samoa (MacKee, 1994; Space & Flynn, 2002; Smith, 1985; Oviedo Prieto et al., 2012; PIER, 2015). According to the IFAS Assessment of Non-Native Plants in Florida’s Natural Areas (Fox et al., 2008), B. purpurea is invasive and not recommended in Florida.

B. purpurea is native to southern and southeastern Asia, although the extent of the native distribution varies between authorities. The Flora of China Editorial Committee (2015) suggests that it is probably only native from Nepal through continental monsoon Asia (i.e., Cambodia, Laos, Myanmar, Thailand, and Vietnam), while Orwa et al. (2009) list it as also native to Indonesia, Japan and Taiwan. It has been actively planted as an ornamental in many tropical and subtropical regions of the world and now it can be found naturalized in North America, Central America, the West Indies, Africa, and on islands in the Indian and Pacific Ocean (Orwa et al., 2009; ILDIS, 2015; PIER, 2015; USDA-ARS, 2015).

The risk of introduction of B. purpurea is moderate to high, principally in areas near cultivation. This species has been actively introduced to be used as an ornamental and produces seeds that are dispersed by wind, water, and by humans. It has repeatedly escaped from cultivation and successfully established and naturalized in natural and disturbed areas throughout tropical and subtropical regions of the world (Connor, 2001; Orwa et al., 2009). 

B. purpurea grows in tropical and subtropical climates. It can be found growing in many vegetation types such as evergreen lowland rainforests, mountain forests, savanna, scrublands, dry deciduous forests and swamp forests on various soils (Contu, 2012). It can also grow in disturbed areas, secondary forest, along roadsides and in gardens, parks, and disturbed sites near urban areas (PROTA, 2015). In the West Indies (i.e., Puerto Rico and Cuba), B. purpurea grows in areas that annually receive at least 1500 to 2500 mm of rainfall, with well-drained and moist soils (Connor, 2001). 

Genetics

The chromosome number reported for B. purpurea is 2n = 28 (Kumari and Bir, 1989).

Physiology and Phenology

B. purpurea is a fast-growing, small tree to medium sized evergreen shrub, reaching 7.6 m in height and 17.8 cm in diameter. It can reach a height of 4.6 m in less than 2 years. Trees start flowering at a very early age of 2-3 years and yield viable seeds (Connor, 2001; Orwa et al., 2009).

In China, B. purpurea produces flowers from September to November and fruits from February to March (Flora of China Editorial Committee, 2015). In other Asiatic areas, it flowers from September to November when the plant is leafless and the seed ripens between February and May, with a tendency to be later in the west than in eastern Asia (Orwa et al., 2009).

Environmental Requirements

B. purpurea grows at elevations from about 500 to 2000 (-3000) metres. It prefers to grow in moist areas with mean annual temperature ranging from 12 to 21ºC and mean annual rainfall between 1000 and 5000 mm. It grows on a variety of sandy, loamy and gravelly soils in full sun in fertile, moisture-retentive but well-drained soils (Orwa et al., 2009). It demands plenty of light and requires good drainage. Severe frost kills the leaves of seedlings and saplings. The species is frost-hardy but less drought-hardy than other species of Bauhinia, though flowers best on dry soils (Orwa et al., 2009). 

Within its native distribution range, borers, mites and larvae of several insects feed on this plant species. Leaf spot and leaf scorch are the two diseases reported for B. purpurea.  It is also susceptible to the viruses Clitoria yellow vein virus and Turnip rosette virus (Orwa et al., 2009).

Animal feed, fodder, forage

• Fodder/animal feed

Environmental

• Agroforestry
• Amenity
• Erosion control or dune stabilization
• Shade and shelter
• Soil improvement
• Windbreak

Fuels

• Fuelwood

General

• Ornamental

Genetic importance

• Gene source

Materials

• Dye/tanning
• Dyestuffs
• Fibre
• Gum/resin
• Miscellaneous materials
• Pesticide
• Wood/timber

Medicinal, pharmaceutical

• Source of medicine/pharmaceutical
• Traditional/folklore

Ornamental

• Seed trade

Pulp

• Short-fibre pulp

Sawn or hewn building timbers

• For light construction

B. purpurea looks similar to Bauhinia monandra and B. variegata. All these species have been listed as naturalized and invasive in many tropical and subtropical countries. These three Bauhinia species can be distinguished by the following differences (Weeds of Australia, 2015):

• Bauhinia variegata is a small tree with relatively large leaves (up to 15 cm wide). Its flowers vary from entirely white to various shades of pink or purple with darker pink or reddish-purple markings and have five fertile stamens.
• Bauhinia monandra is a small tree with relatively large leaves (up to 20 cm wide). Its flowers are pale pink or whitish with darker pink or reddish-purple markings and have a single fertile stamen.
• Bauhinia purpurea is a small tree with relatively large leaves (up to 20 cm wide). Its flowers vary from pale purple to bright pinkish-purple and have three fertile stamens.

01/12/15 Original text by:

Julissa Rojas-Sandoval, Department of Botany-Smithsonian NMNH, Washington DC, USA