| Bauhinia× blakeana | |
|---|---|
.jpg) | |
| Flower | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Fabales |
| Family: | Fabaceae |
| Genus: | Bauhinia |
| Species: | B. × blakeana |
| Binomial name | |
| Bauhinia× blakeana | |
Bauhinia ×blakeana (bow-HIN-ee-ə [cross]blayk-ee-AH-nə[2]), commonly called theHong Kong orchid tree,[3] is ahybridleguminous tree of thegenusBauhinia. It has large thick leaves and striking purplish red flowers. The fragrant, orchid-like flowers are usually 10 to 15 centimetres (3.9 to 5.9 in) across, and bloom from early November to the end of March. Although now cultivated in many areas, it originated inHong Kong in 1880 and apparently all of the cultivated trees derive from one cultivated at theHong Kong Botanical Gardens and widely planted in Hong Kong starting in 1914.[4] It is referred to asbauhinia in non-scientific literature though this is the name of the genus. It is sometimes called theHong Kong orchid (Chinese:香港蘭;Cantonese Yale:Hēunggóng làahn). In Hong Kong, it is most commonly referred to by its Chinese name of洋紫荊(yèuhng jígīng).
TheBauhinia double-lobed leaf is similar in shape to a heart or a butterfly, or a camel's footprint - hence the common name camel's foot.[citation needed] A typical leaf is 7 to 10 centimetres (2.8 to 3.9 in) long and 10 to 13 centimetres (3.9 to 5.1 in) wide, with a deep cleft dividing the apex. In Hong Kong the leaf is known as the "clever leaf" (聰明葉;chūngmìhng yihp), and is regarded as a symbol of wisdom. Some people use the leaves to make bookmarks in the hope that they will bring them good luck in their studies.
It is sterile, which means it does not generally produce seeds or fruits, and is ahybrid betweenBauhinia variegata andBauhinia purpurea.[4][5] The 2008 research was able to identify the female parent asBauhinia purpurea, but it could not differentiate the male parent fromBauhinia variegata var.variegata orBauhinia variegata var.candida. This is not unexpected, asBauhinia variegata var.candida is a white-flowered form ofBauhinia variegata var.variegata, and not a separate species or sub-species. The 2005 research suggestedBauhinia ×blakeana is genetically closer toBauhinia variegata, while the 2008 research indicated it is closer toBauhinia purpurea instead. In 2025 the Bauhinia Genome Project definitively determined through a completetelomere-to-telomere reference assembly thatBauhinia purpurea is the maternal parent, andBauhinia variegata the parental strain. Also supporting the hypothesis thatBauhinia × blakeana more likely originated from a rare single, recent hybridization event rather than recurrent gene flow.[6]
Propagation is by grafting. As it is only known in cultivation, it can also be named as acultivar:Bauhinia 'Blakeana'.[4] Hong Kong orchid trees are usually sterile, yet here, too, there are exceptions. One tree has been found in Hong Kong that produces seeds, perhaps indicating that evolution or mutation has occurred, or that even thoughBauhinia ×blakeana is perhaps sterile when self-pollinated (the scientific study in 2005 established the low fertility ofBauhinia ×blakeana's pollen when compared with its parental speciesBauhinia purpurea orBauhinia variegata), however, it may perhaps be able to produce seeds when pollinated instead by its parental speciesBauhinia purpurea orBauhinia variegata or other relatedBauhinia species. More scientific research will need to be carried out, e.g., artificial controlled cross-pollination experiments to confirm the ability ofBauhinia ×blakeana inbackcross oroutcross to produce (fertile) seeds.
Lawrence Ramsden of theUniversity of Hong Kong's Department of Botany is conducting the search to find out if there are any more individuals that can produce seeds – if so, they could benefit propagation of the tree for horticulture.[7] Two previous instances of seeds found fromBauhinia ×blakeana specimens failed to germinate.[5] Development of seed pods (but no seeds) fromB. ×blakeana have been observed on three trees in Tai Po and Kowloon in Hong Kong. These threeB. ×blakeana trees with numerous seed pods were grown alongsideB. purpurea,B. variegata (white flowered form) andB. variegata. At the time (March in Hong Kong), bothB. blakeana andB. purpurea were flowering, therefore, the pollens for development ofB. blakeana seed pods may have been contributed fromB. purpurea.[8]
This tree was discovered in around 1880 by a French Catholic Missionary of theParis Foreign Missions (MEP), near the ruins of a house above the shore-line of westernHong Kong island nearPok Fu Lam and propagated to the formal botanical gardens in Victoria/Central.[4]
The first thorough scientific description of the tree was made byStephen Troyte Dunn, Superintendent of the Botanical and Forestry Department, who assigned it to the genusBauhinia in his paper of 1908.[9] Dunn named the tree for "Sir Henry and Lady Blake", the former beingSir Henry Blake,British Governor of Hong Kong, from 1898 to 1903. Sir Henry and Lady Blake were thus thanked for their promotion of the Hong Kong Botanic Gardens.
Dunn's description was based on the trees in the Hong Kong Botanical Gardens, which had been grown from cuttings taken from trees cultivated in the French Mission atPokfulam, on the west coast of Hong Kong Island, which in turn were derived from a tree (or trees) found nearby. As far as is known, all the French Mission cuttings were taken from a single tree, so all Hong Kong orchid trees today would beclones of the original tree. Dr Lawrence Ramsden of the University of Hong Kong’s Department of Botany estimates that this clonal origin would mean thatB. ×blakeana could be susceptible to decimation by epidemics, though it has so far avoided major diseases.
In order to avoid the susceptibility ofB. ×blakeana to diseases due to the lack of genetic diversity from the current clones of a singleB. ×blakeana tree back in 1880s, efforts should be made to re-hybridise the parental species ofB. ×blakeana, ie, crossingB. purpurea andB. variegata to generate new hybrid specimens ofB. ×blakeana instead to add new genetic materials to the current stock ofB. ×blakeana.
To solve the mystery of Hong Kong Bauhinia's parentage a community crowdfunded Bauhinia Genome project was launched in 2015,[10] finally completing the genome and determing the maternal and parenal species in 2025.[6]
Since 1997 the flower appears on Hong Kong's coat of arms,its flag andits coins; its Chinese name has also been frequently shortened as 紫荊/紫荆 (洋yáng means 'foreign' in Chinese, and this would be deemed inappropriate by the PRC government[citation needed]), although 紫荊/紫荆 refers to another genus calledCercis. Astatue of the plant has been erected inGolden Bauhinia Square in Hong Kong.Although the flowers are bright pinkish purple in colour, they are depicted in white on the Flag of Hong Kong.Hong Kong Airlines uses BAUHINIA as itscallsign.
Theendemic plant ofHong Kong was introduced toTaiwan in 1967. In 1984 it was chosen to be the city flower ofChiayi City, in southwesternTaiwan.
| Bauhinia × blakeana | |||||||||||||||
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| Traditional Chinese | 洋紫荊 | ||||||||||||||
| Simplified Chinese | 洋紫荆 | ||||||||||||||
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Media related toBauhinia × blakeana at Wikimedia Commons