The Bauhinia x blakeana Dunn was first chosen as the City Flower of Hong Kong in 1965. The species was later on selected to be the regional emblem of the Hong Kong Special Administrative Region on 1 July 1997 when Hong Kong returned to the Chinese sovereignty. Bauhinia x blakeana has been widely cultivated in parks, gardens as well as roadside amenity areas in Hong Kong and other parts of the world. Its interesting leaf form and showy flowers throughout the winter months make this handsome tree well known to most of our citizens. However, not many of us would know its history and how it was discovered in this world.
This species was first mentioned in the Report on the Botanical and Afforestation Department for the Year 1903. The report described, "The mysterious origin of the tree and its magnificent flowers at once arrest the interest. A tree of it was discovered between 20 and 30 years ago in the woods on Mount Davis from which it was introduced by its finder into the gardens of the Pokfulum Sanatorium and from there to the Botanic Gardens. So far, all efforts to identify them with any foreign species have failed".
Specimens had subsequently been compared in the Kew in Britain and other herbaria, but without the discovery of any similar plant elsewhere. Until 1908, the then Superintendent of the Botanical and Afforestation Department, Mr. S. T. Dunn described the tree in Latin and formally published it as a new species in the Journal of Botany. Mr. Dunn added in the article that, "It is indeed to the Fathers of the above Mission (Missions Etrangeres at Pokfulam) that we owe the preservation of the Bauhinia. It was discovered by them near the ruins of a house on the sea-shore; from the trees thus produced the Botanic Gardens were supplied." The species Bauhinia x blakeana was named after Sir Henry and Lady Blake to commemorate the kind interest taken in the Botanic Gardens by them. Sir Henry Blake was the Governor of Hong Kong from 1898 to 1903.
Bauhinia x blakeana was propagated by cutting, grafting or air-layering. All the individuals we see today are probably the direct descendants of the one first cultivated in Botanic Gardens.
Aquilaria sinensis (Lour.) Gilg, with a common name "incense tree", is an evergreen tree species native to South China. Its trunk is smooth and light grey, leaves are oval-shaped with fine vines, and flowers are small and yellowish green. In summer, plenty of oval-shaped green fruits can be seen hanging on it. It is a useful plant as the resin extracted from wood can be used for making incense and Chinese medicine, its wood for joss sticks, and its bark for paper. It has been listed as a Wild Plant under State Protection (Category II) in China owing to the decline in its distribution. However, Aquilaria sinensis is common in Hong Kong and currently not under any threat.
What is the relationship between this handsome tree and the name of the place we are living in? Despite various explanations for the origin of the name of Hong Kong, the most popular belief is that Hong Kong derives its name from "Fragrant Harbour" or "Incense Harbour".
According to "Hong Kong and Its External Communication before 1842", a book written by Professor Lo Hsiang-lin and other reference materials, incense tree was planted in large numbers in Tung Koon (Dongguan) District and the New Territories of Hong Kong, particularly at Lik Yuen (Shatin) and Sha Lo Wan (the west of Lantau Island) during the Sung Dynasty (619-970 A.D.). The products of incense tree, pieces of incense each shaped like an amber, were transported through land routes from the production areas to Tsim Sha Tau (now Tsim Sha Tsui) and then by sampan to Shek Pai Wan (now Aberdeen), where incense products were finally exported to destinations in the Mainland China, Southeast Asia and places as far as Arabia. Shek Pai Wan, the harbour exporting incense, was therefore named 'Fragrant Harbour' ('Heung Harbour'), to the extent that the whole island was later known as Hong Kong.
However, during the early Ching (Qing) Dynasty (1662-1720 A.D.), in order to counter the coastal attacks by pirates, all coastal habitants were evacuated to inlands. Therefore, the planting industries of incense tree were seriously affected.
Now, the harvesting of incense tree for economic uses has disappeared in Hong Kong. As the climate and soil condition in Hong Kong are suitable for the growth of incense tree, it becomes a common tree species found in our countryside.
The original vegetation of Hong Kong no longer exists after centuries of human disturbance through his fire and axe. The existing vegetation is the secondary forest developed in the latter half of the twentieth century after the Second World War. The major types of vegetation in Hong Kong are woodland, shrubland and grassland. Minor formations occur in special habitats in relation to the freshwater and coastal environments.
There are also small but well-developed woodlands associated with many of the older villages and temples. These are the "Fung Shui Woods" ("Sacred or Lucky Groves"), which owe their existence to the protection afforded by the villagers in accordance with ancient traditions. These woodlands are often enriched by the planting of Aquilaria sinensis, Cinnamomum camphora, and fruit trees such as Euphoria longan, Litchi chinensis, Syzygium jambos and clumps of bamboos.
Many hillslopes have been reforested with Acacia confusa, Pinus massoniana, Pinus elliottii, Eucalyptus species and Lophostemon confertus. In recent years, more native trees have been planted on hillslopes, including Machilus chekiangensis, Castanopsis fissa, and Schima superba. Bamboos in Hong Kong are scattered and shrubby. Common species are Arundinaria hindsii, Arundinaria shiuyingiana, A. cantorii, and Indocalamus sinicus.
Mikania (Mikania micrantha Kunth) is an exotic perennial herbaceous vine belonging to the family Asteraceae (Compositae). It is originated from tropical South and Central America but is now widely distributed in India, Southeast Asia, Pacific islands and South China including Guangdong and Hong Kong.
Similar to the habit of other climbers, Mikania climbs up other plants to reach the canopy for better sunlight. Even worse, its leaves grow vigorously and will cover up other plants eventually causing damage or even killing other plants by cutting out the light for photosynthesis and smothering them. Mikania sprawls out rapidly in spring and summer which is the reason for its name "mile-a-minute weed". Moreover, it reproduces efficiently both sexually by seeds, and vegetatively by rooting at nodes.
Mikania has characteristic opposite, heart-shaped leaves, margins irregularly coarsely toothed, 4 - 13cm long. Mikania has much branched and hairless stems, and numerous small heads of densely clustered white flowers with fragrant. Mikania produces small seeds, black in colour, with a terminal tuft of white bristles for wind dispersal.
Upon receipt of enquires or complaints on Mikania related issues, a site visit would normally be required to confirm the species of climbing plant of concern and to assess the habitat and vegetation affected. Particular attention should be paid to the climbing plant in question as it could be our native species such as Climbing Bauhinia (Bauhinia glauca) and Spiny-fruited Vine (Byttneria aspera) which commonly occur in Hong Kong as part of our biodiversity. In such cases, it is not desirable to clear the climbers which would cause unnecessary disturbance to the natural vegetation cover and may even create a niche for Mikania to invade.
At the time being, it would be impossible to eradicate Mikania completely in Hong Kong, as it has already taken root in many locations. When considering a request for clearing Mikania, one should firstly assess the priority according to the impacts on vegetation and landuse of the site in question. In general, priority should be given to control the spreading of Mikania at ecologically important areas such as Country Parks, Special Areas and SSSIs and to clear Mikania where mature trees and woodland habitat have been adversely affected. On the contrary, removal of Mikania on derelict fields or disturbed sites may not be justified unless the situation is very unsightly causing public concerns. Site accessibility should also be duly considered as some sites affected by Mikania are on difficult terrains or at remote areas where access would be impracticable.
Agriculture, Fisheries and Conservation Department conducts regular monitoring in Country Parks, Special Areas and SSSIs and would remove Mikania to prevent spreading of this weed in these areas as far as practicable. Other concerned departments would arrange clearing of Mikania affecting the natural vegetation and landscape features in areas under their jurisdictions where warranted. Landowners and management agents of private housing estates should be responsible for the locations within their properties. Various departments or concerned parties may appoint landscape contractors, skilled landscape workers or gardeners to clear Mikania in areas under their jurisdictions. AFCD has also prepared a Practice Note on clearing Mikania for interested parties for general reference.
In principle, the best way to protect woodland and trees from damage by Mikania is to monitor the situation with regular maintenance to control its spreading. Depending on the intended landuse of the site in question, planting trees and shrubs at the site may be considered as a long-term measure to control Mikania. In addition, disturbance and fragmentation on natural woodland should be avoided as far as possible in order not to create woodland edges which are susceptible to Mikania invasion.