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SOME OUTLINES ABOUT ORCHIDS OF VIETNAM ?
Among the Vietnamese flora, Orchidaceae constitutes one of the families having the highest number of species within the flowering plants. In our opinion, the Vietnamese Orchidaceae encompasses around 140 genus and over 800 species. Being a second largest family of the flowering plants after the Asteraceae and the largest family among the Monocotyledons (Liliopsida) it characterizes the opulence of this family all over the world: 750 genus and over 25.000 species (after A. L. Takhtajan 1987).
In general, the Orchidaceae includes all perennial plants which either grow on soils, in rock crevices (Lithophytes) or epiphytically or in saprophytes
When living on soils, they often give heavy bulbs or roots or creeping stems Flowers either appear simultaneously with leaves or after the fall of the latters.
In saprophytic, they develop sucking roots in order to extract nutritive sub stances from humus (which often is constituted by grass roots) decomposing by means of fungus. The stem and leaves do not bear the green colour (or there are no leaves) but the flowers still blossom in many bright colours
Nevertheless, the most peculiar line of the Orchidaceae lies in their epiphytic line which drives from creeping, adhering or hanging to the back of other trees. There either belong to the monopodial Orchids with numerous earial roots which retain their stems, or provide them which nutrient substances and water collected from the atmosphere., or they
belong to the sympodial Orchids which have a developed system of thin and dense roots. Their leaves stem from glossy pseudobulbs in green or brown or pink shades and bearing
beautiful white or yel1ow veins.
In the vegetal world Orchids offer the widest variety. Ordinarily, the flower shall presents six segments arranged in two circles ornamented with three multicolored sepals sized as petals. The flower-cup can be loose or bound at the base. The two laterals petals look very much like the sepals, while the petals in the middle are coloured with changing shades, the latters are called labellum or lip, and they are where insects alight and pollinate, at the base of the lip lies the spur.
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The One Colored Paphiopedilum - Paphiopedilum concolor - Picture: Phung My Trung |
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Centered in the flower is the column, a finger like structure that carries the reproductive parts-the pollimia and stigmatic surface.
The pollination of Orchids is carried by insects, and this is a harmonious phenomenon of Nature occuring along a very accurate pattern (Orchids are often twisted by 180 degrees so that the lip can be directed outward).
The fruit of Orchids belong to the kind of loculicidaled capsule, opening along 3 to 6 longtitudinal fissures. Seeds are in considerable quantity and their size minuscule rendering them uprightless and easy to be carried very far by the wind
THE CLASSIFICATION
Orchids of Vietnam have the following nomenclature: Orchidaceae A. L. de Jussieu (including Apostasiaceae Lindley 1833; Cypripedlaceae Lindley 1833; Limodoraceae Horaninow 1847; Neottialceae Horaninow 1834; Vanil1aceae Lindley 1835 is classified ln six subfamilies and following tribes.
1- Apostasioideae, with species: Neuwiedia, Apostasia.
2.Cypripedioideae, with specles: Paphiopedlium...
3. Neottioideae, with tribes:
- Epipactideae, represented by specles: Cephaianthera, Epipactis...
- Neottieae, represented by species. Listera, Goodyera, Erythrodes, Ludisia, Anoectochilus, Zeuxine, Spiranthes.
4. Orchidoideae: with tribes:
- Orchideae, represented by species: Platanthera, Habenaria…
5.Epidendroideae, with tribes:
- Arethuseae, represented by species: Thunia, Phaius, Calanthe, Bletilla…
- Vanilleae, represented by species: Vanilia, Galeola
- Gastrodieae, represented by species: Nervilia...
- Epipogieae, represented by species: Epipogieum...
- Coelogyneae, represented by species: Coelogyne,
- Malaxideae, represented by species: Liparis, Malaxis, (Microstylis), Oberonia…
- Epidendreae, represented by species: Eria, Dendrobium, Flickingeria, Bulbophyllum…
6.Vardoideae, with following tribes:
- Polystachyeae, represented by species: Polystachys…
- Cymbidieae,represented by species: Eulophia, Cymbidium, Grammatophyllum,...
- Vandeae, represented by species: Phalaenopsis, Kingidium, Doritis, Aerides, Vanda, Arachnis, Renanthera, Cleisostoma, Taeniophyllum.
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Calanthe cardioglossa - Picture: Phung My Trung |
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THE DISTRIBUTION
Vietnam belongs to South-East Asia, and is completely included in the tropics of the Northern hemisphere. It possesses a fairly peculiar geographic location, at the same time being attached to the Euro-Asian continent (belonging to the Eastern and Southern side of the Asian continent) and opening to the ocean.
Being one end of the Asian continent, Vietnam hosts numerous species and genus of Orchids migrated from Northern and West-Northern regions, which comprise mainly temperate variaties coming from Himalaya’s bases and from Southern China. These breeds of Orchids offer a wide range variety and grow ordinarily in high and medium Northern mountains. Sometimes, they can also be found in more meridional mountains where they diversity into many new species with are characteristic of Vietnamese cold climate regions.
On the other side, Vietnam has a rather long coast stretching on 3.260 km and located in the very center of the monsoon winds of South-East Asia. That is why, although situated rather near the equator, the weather is not closed to draught but rather yields high annual rain levels. With two sides (Eastern and East-Southern sides) looking to the sea and facing winds, Vietnam offers sufficent conditions towards the migration of Orchids species from Malaysia, Indonesia, this leads to the making of a variety of Orchids bearing
entirely tropical characteristics of Southern low hills and mountains. The more one heads inward, the more finds mainly hills and mountains, with plains being only one fifth of the
territory.The mountains are part of an impressive and varied chain with divide strongly the geography of the country, thus creating favourable conditions for maintaining the reproduction of endemic Orchids species and giving birth to specific orchid races with restricted distribution.
Althought the weather in Vietnam is allyear round humid and windy, the presence of the Truong Son Mountains chain running along the whole country has created many distinct ecologies with distinct climates. This has lead to a very specific distribution of very diverse Orchids species on restricted areas as well as along different latitudes. As an example, if the South and the Highlands have a tropical and all the year round hot weather with a rainy season distinct from a dry season;on the contrary, the Northern and Northern central weather clearly show a cold winter accompanied with drizzles. Orchids in Southern provinces are mainly constituted by species showing two separate growing seasons: during the dry season, their leaves ordinarily fall and their growth stalls (especially with the terrestrial Orchids); only in the rainy season do they grow shoots and luxurious leaves for finally blossoming into multicoloured and scented flowers. On the other hand, Orchids in the North do rarely abandon their leaves, they only stop growing by the end of Autumn-beginning of Winter for afterwards blossoming in Springtime into shoots and flowers.
In brief, from South to North, from plains to mountains, the Vietnamese orchids flora shows a very diverse opulence. This flora encompasses particular species and migrated genus from North and South, with representatives of fully tropical characteristic as well as temperate regions such as South- Eastern parts of the Asian continent.
It is, however, possible to classify Vietnamese Orchids along six following regions
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Chiloschista parishii - Picture: Phung My Trung |
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1 The Eastern-North
Located Northern most of Vietnam, this region stretches from the Gulf of Tonkin to the 1eft bank of the Red River and hosts the coldest climate of the country. This is center of distribution of the Asian-tropical species as well as of the tropical ones which evidence clear influences from Himalayan Orchids and South- China Orchids such as Cymbidium,
Phalaenopsis, Vanda, Paphiopedilum…and from cold weather accommodating species such as Dendrobium, Coelogyne…
2. The Western North
Stretching from the right bank of Red-River (the Convoi mountain bases) to the mountainous region adjacent to Laos-Although located at the same latitude, but due to the presence of mountainous chain acting like shields against cold Northern winds, the weather here is less cold, on the contrary, Summer begins sooner and is accompanied by Laotian winds. Orchids in this area can better withstand the hot weather and belong to the Eria, Bulbophyllum, Rhynchostylis, Dendrobium…they are closed to Orchids growing in the Laotian Highlands.
3. The Northern Truongson (which includes all the Northern plain)
Stretching from the right bank of the Ca river to Quang Nam province.This constitutes the transience between the Northern and the Southern Orchids systems with the largest part of Orchids belonging to the tropical species such as Habenaria, Phaius, Spiranthes, Flickingeria, Dendrobium, Corymborkis…scattered among high mountain peaks. Aside
These, there are also the Paphiopedilum, Cymbidium which accommodate fresh and humid weathers.
4. The Southern Truongson, or more accurately
The South-central Highlands; due to an irregular geographic location and a complex climate, the Orchids of this region bear both characteristics of tropical high mountains and of the Asian tropics, they belong to the Coelogyne, Pholidota, Aerides, Eulophia, Calanthe, Goodyera, Anoectochilus…
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Dendrobium bellatulum - Picture: Phung My Trung |
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In correspondence with the contrasted forests, the Orchids also have their peculiar representatives such as the kinds living in dry forests which change their leaves ("Khop" forests): these terrestrial Orchids exhibit large bulbs and wither away in dry seasons, develop only leaves and flowers in rainy seasons. Another kind lives epiphytally and grows old and fat bulbs or wood stems enabling them a persistent subsistence: these Orchids lose leaves in the dry season and belong to the Bulbophyllum, Eria, Cleisostoma, Liparis…In contrast to the above, Orchids growing in swampy grounds can sustain high humidity levels and belong to the Calanthe, Bromheadia, Eulophia…
5. The Southern plain
Is constituted by the whole triangle including the Mekong river and the remaining low mountains of the Truongson Mountainous chain. The weather here is completely tropical with distinct rainy and dry seasons. Orchids are mainly tropical ones belonging to the Bulbophyllum, Agrostophyllum, Acriopsis, Acampe, Trichoglottis, Dendrobium, Eria…
6. The Island Regions
Vietnam possesses thousands of different size islands which in certain part gather into archipelagos such as Phuquoc, Conson…these Orchids have close resemblance with those growing in low mountains and include the Bulbophyllum, Acampe, Apotasia, Galeola, Malaxis, Liparis, Podochilus, Eria…
In brief, the family of Orchids is present in nearly all kinds of forests in Vietnam. However, centers where is found the widest diversity are still scattered along the Northern mountains chain and Truong Son Mountainous chain. It is here that one might always discover new species which come to enrich the Orchids of Viet Nam
Trần Hợp – Phùng Mỹ Trung
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