View source for Bauhinia × blakeana

{{Short description|Species of legume}}
{{distinguish|Bauhinia purpurea}}
{{Speciesbox
|image = Bauhinia blakeana (Key West).jpg
|image_caption = Flower
|genus = Bauhinia
|species = × blakeana
|authority = [[Stephen Troyte Dunn|Dunn]]<ref name=POWO_481142-1/>
}}

'''''Bauhinia'' × ''blakeana''''' ({{Respell|bow-HIN-ee-ə}} [cross] {{Respell|blayk-ee-AH-nə}}<ref name=Coom94/>), commonly called the '''Hong Kong orchid tree''',<ref>{{GRIN | ''Bauhinia'' × ''blakeana'' | access-date = 15 December 2017}}</ref> is a [[Hybrid (biology)#In plants|hybrid]] [[legume|leguminous]] tree of the [[genus]] ''[[Bauhinia]]''. It has large thick leaves and striking purplish red flowers. The fragrant, orchid-like flowers are usually {{Convert|10|to|15|cm|in}} across, and bloom from early November to the end of March. Although now cultivated in many areas, it originated in [[Hong Kong]] in 1880 and apparently all of the cultivated trees derive from one cultivated at the [[Hong Kong Zoological and Botanical Gardens|Hong Kong Botanical Gardens]] and widely planted in Hong Kong starting in 1914.<ref name="lau" />  It is referred to as '''bauhinia''' in non-scientific literature though this is the name of the genus.  It is sometimes called the '''Hong Kong orchid''' ({{lang-zh|c=香港蘭|cy=Hēunggóng làahn|first=j,t}}). In Hong Kong, it is most commonly referred to by its Chinese name of {{lang|zh-Hant-HK|洋紫荊}} ''(yèuhng jígīng)''.

The ''Bauhinia'' 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|date=October 2021}} A typical leaf is {{Convert|7|to|10|cm|in}} long and {{Convert|10|to|13|cm|in}} wide, with a deep cleft dividing the apex. In Hong Kong the leaf is known as the "clever leaf" ({{lang-zh|c=聰明葉|cy=chūngmìhng yihp|labels=no|first=j,t}}), 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 a [[Hybrid (biology)|hybrid]] between ''[[Bauhinia variegata]]'' and ''[[Bauhinia purpurea]]''.<ref name="lau">{{citation | doi = 10.3732/ajb.92.3.525 | title = Hybrid origin of "Bauhinia blakeana" (Leguminosae: Caesalpinioideae), inferred using morphological, reproductive, and molecular data | year = 2005 |author1=Lau, C. P. Y. |author2=Ramsden, L. |author3=Saunders, R. M. K. | journal = American Journal of Botany | volume = 92 | pages = 525–33 | issue = 3 | pmid = 21652431 | doi-access = free }}</ref><ref name=Mak>{{citation | doi = 10.1111/j.1744-7909.2007.00591.x |date=Jan 2008 |author1=Mak, Cy |author2=Cheung, Ks |author3=Yip, Py |author4=Kwan, Hs | title = Molecular evidence for the hybrid origin of ''Bauhinia blakeana'' (Caesalpinioideae) | volume = 50 | issue = 1 | pages = 111–8 | issn = 1672-9072 | pmid = 18666958 | journal = Journal of Integrative Plant Biology |bibcode=2008JIPB...50..111M }}</ref> The 2008 research was able to identify the female parent as ''[[Bauhinia purpurea]]'', but it could not differentiate the male parent from ''Bauhinia variegata'' var. ''variegata'' or ''Bauhinia variegata'' var. ''candida''. This is not unexpected, as ''Bauhinia variegata'' var. ''candida'' is a white-flowered form of ''Bauhinia variegata'' var. ''variegata'', and not a separate species or sub-species. The 2005 research suggested ''Bauhinia'' × ''blakeana'' is genetically closer to ''[[Bauhinia variegata]]'', while the 2008 research indicated it is closer to ''[[Bauhinia purpurea]]'' instead. In 2025 the Bauhinia Genome Project definitively determined through a complete [[T2T|telomere-to-telomere]] reference assembly that ''[[Bauhinia purpurea]]'' is the maternal parent, and ''[[Bauhinia variegata]]'' the parental strain. Also supporting the hypothesis that ''Bauhinia × blakeana'' more likely originated from a rare single, recent hybridization event rather than recurrent gene flow.<ref name=":0">{{Cite journal |last1=Mu |first1=Weixue |last2=Darian |first2=Joshua Casey |last3=Sung |first3=Wing-Kin |last4=Guo |first4=Xing |last5=Yang |first5=Tuo |last6=Tang |first6=Mandy Wai Man |last7=Chen |first7=Ziqiang |last8=Tong |first8=Steve Kwan Hok |last9=Chik |first9=Irene Wing Shan |last10=Davidson |first10=Robert L |last11=Edmunds |first11=Scott C |last12=Wei |first12=Tong |last13=Tsui |first13=Stephen Kwok-Wing |date=2025-01-01 |title=The haplotype-resolved T2T genome for Bauhinia × blakeana sheds light on the genetic basis of flower heterosis |journal=GigaScience |volume=14 |article-number=giaf044 |doi=10.1093/gigascience/giaf044 |issn=2047-217X |pmc=12012898 |pmid=40276955}}</ref>

Propagation is by grafting. As it is only known in cultivation, it can also be named as a [[cultivar]]: ''Bauhinia'' 'Blakeana'.<ref name="lau"/> 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 though ''Bauhinia'' × ''blakeana'' is perhaps sterile when self-pollinated (the scientific study in 2005 established the low fertility of ''Bauhinia'' × ''blakeana'''s pollen when compared with its parental species ''Bauhinia purpurea'' or ''Bauhinia variegata''), however, it may perhaps be able to produce seeds when pollinated instead by its parental species ''Bauhinia purpurea'' or ''Bauhinia variegata'' or other related ''Bauhinia'' species. More scientific research will need to be carried out, e.g., artificial controlled cross-pollination experiments to confirm the ability of ''Bauhinia'' × ''blakeana'' in [[Backcrossing|backcross]] or [[Outcrossing|outcross]] to produce (fertile) seeds.

Lawrence Ramsden of the [[University of Hong Kong|University 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.<ref>{{cite web |title=How to Join the Hunt for ''Bauhinia'' Seeds |url=http://web.hku.hk/~lramsden/bauhjoin.html |access-date=2014-07-15 |url-status=dead |archive-url=https://web.archive.org/web/19991013043744/http://web.hku.hk/~lramsden/bauhjoin.html |archive-date=1999-10-13 }}</ref> Two previous instances of seeds found from ''Bauhinia'' × ''blakeana'' specimens failed to germinate.<ref name=Mak/> Development of seed pods (but no seeds) from ''B.'' × ''blakeana'' have been observed on three trees in Tai Po and Kowloon in Hong Kong. These three ''B.'' × ''blakeana'' trees with numerous seed pods were grown alongside ''B. purpurea'', ''B. variegata'' (white flowered form) and ''B. variegata''. At the time (March in Hong Kong), both ''B. blakeana'' and ''B. purpurea'' were flowering, therefore, the pollens for development of ''B. blakeana'' seed pods may have been contributed from ''B. purpurea''.<ref>[http://www.hktree.com/diary/17w05.htm "誰說洋紫荊不結果", ''Ken Lau手記'']</ref>

==History==
[[File:Hong Kong Orchid tree flower.jpg|thumb|220px|Flower]]
This tree was discovered in around 1880 by a French Catholic Missionary of the [[Paris Foreign Missions Society|Paris Foreign Missions]] (MEP), near the ruins of a house above the shore-line of western [[Hong Kong island]] near [[Pok Fu Lam]] and propagated to the formal botanical gardens in Victoria/Central.<ref name="lau" />

The first thorough scientific description of the tree was made by [[Stephen Troyte Dunn]], Superintendent of the Botanical and Forestry Department, who assigned it to the genus ''Bauhinia'' in his paper of 1908.<ref>{{cite journal|url=https://www.biodiversitylibrary.org/item/109571#page/377/mode/1up|title=New Chinese Plants|author=S. T. Dunn|pages=324–326|journal=Journal of Botany, British and Foreign|volume=46|issue=550|year=1908}}, Page 325</ref> Dunn named the tree for "Sir Henry and Lady Blake", the former being [[Sir Henry Blake]], [[Governor of Hong Kong|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 at [[Pok Fu Lam|Pokfulam]], 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 be [[Cloning|clones]] of the original tree. Dr Lawrence Ramsden of the University of Hong Kong’s Department of Botany estimates that this clonal origin would mean that ''B.'' × ''blakeana'' could be susceptible to decimation by epidemics, though it has so far avoided major diseases.

In order to avoid the susceptibility of ''B.'' × ''blakeana'' to diseases due to the lack of genetic diversity from the current clones of a single ''B.'' × ''blakeana'' tree back in 1880s, efforts should be made to re-hybridise the parental species of ''B.'' × ''blakeana'', ie, crossing ''[[Bauhinia purpurea|B. purpurea]]'' and ''[[Bauhinia variegata|B. variegata]]'' to generate new hybrid specimens of ''B.'' × ''blakeana'' instead to add new genetic materials to the current stock of ''B.'' × ''blakeana''.

To solve the mystery of Hong Kong Bauhinia's parentage a community crowdfunded Bauhinia Genome project was launched in 2015,<ref>{{Cite web |date=2015-11-07 |title=Unique project to sequence the genome of the Hong Kong bauhinia tree |url=https://www.scmp.com/magazines/post-magazine/article/1875917/unique-project-sequence-genome-hong-kong-bauhinia-tree |access-date=2025-05-10 |website=South China Morning Post |language=en}}</ref> finally completing the genome and determing the maternal and parenal species in 2025.<ref name=":0" />

==Usage as an emblem==
[[File:HKUrbanCouncil.svg|thumb|''Bauhinia'' × ''blakeana'' was adopted as the [[National emblem|floral emblem]] of [[Hong Kong]] by the [[Urban Council, Hong Kong|Urban Council]] in 1965.]]
[[File:Urban Council of Hong Kong Armorial Bearings.png|thumb|Historical Urban Council of Hong Kong armorial bearings, granted by the [[College of Arms]] in 1979. The council was abolished on 31 December 1999.]]
[[Image:Flag of Hong Kong.svg|thumb|right|The [[flag of Hong Kong]] Special Administrative Region of the People's Republic of China in 1997.]]
Since 1997 the flower appears on Hong Kong's coat of arms, [[Flag of Hong Kong|its flag]] and [[Hong Kong dollar|its 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|date=July 2020}}), although 紫荊/紫荆 refers to another genus called ''[[Cercis]]''. A [[statue]] of the plant has been erected in [[Golden 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 its [[Aviation call signs|callsign]].

The [[endemic (ecology)|endemic]] plant of [[Hong Kong]] was introduced to [[Taiwan]] in 1967.  In 1984 it was chosen to be the city flower of [[Chiayi|Chiayi City]], in southwestern [[Taiwan]].
{{Infobox Chinese|t=洋紫荊|s=洋紫荆|j=joeng4 zi2 ging1|y= yèuhng jígīng|p=yáng zǐjīng|ci={{IPAc-yue|j|oeng|4|-|z|i|2|-|g|ing|1}}}}

==Gallery==
<gallery>
File:Tree I IMG 2075.jpg|Tree in [[Kolkata]], [[West Bengal]], [[India]].
File:Flowers I IMG 2101.jpg|Flowers in Kolkata
File:Leaf I MG 2069.jpg|Leaf in Kolkata
File:Flower buds I IMG 2064.jpg|Flower buds in Kolkata
File:Bark I IMG 2073.jpg|Bark in Kolkata
File:Bauhinia × blakeana.jpg|flower in [[Ajmiriganj Upazila|Ajmiriganj]], [[Sylhet]], [[Bangladesh]]
</gallery>

==References==
{{Reflist|refs=
<ref name=Coom94>{{Cite book |last=Coombes |first=Allen J. |year=1994 |title=Dictionary of Plant Names |location=London |publisher=Hamlyn Books |isbn=978-0-600-58187-1 |page=22}} Respelling pronunciation slightly adapted as per [[Help:Pronunciation respelling key]].</ref>

<ref name=POWO_481142-1>{{cite web |title=''Bauhinia'' × ''blakeana'' Dunn |work=Plants of the World Online |publisher=Royal Botanic Gardens, Kew|url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:481142-1 |access-date=2020-05-27 }}</ref>
}}

==External links==
* [https://web.archive.org/web/20191106050407/https://readnational.com/national-flower-hong-kong-bauhinia/ National Flower of Hong Kong]
* {{Commons-inline}}
* [http://martinwilliams.tripod.com/hkwildstars/bauhinia.html Bauhinia – Hong Kong emblem]
* [https://web.archive.org/web/20051126085028/http://web.hku.hk/~lramsden/bauhinintro.html Hong Kong Bauhinias]

{{Hong Kong topics}}
{{Taxonbar|from=Q378062}}

{{DEFAULTSORT:Bauhinia blakeana}}
[[Category:Bauhinia|blakeana]]
[[Category:Culture of Hong Kong]]
[[Category:Regional symbols of Hong Kong]]
[[Category:Garden plants of Asia]]
[[Category:Ornamental trees]]
[[Category:Hybrid plants]]
[[Category:Fabales of Asia]]
[[Category:Taxa named by Stephen Troyte Dunn]]