Asian flora

The continent of Asia embraces at least four of the world's major floristic units, namely the Siberian region, the Sino-Japanese region, the Western and Central Asiatic region, and the Indo-Malaysian region.

The Siberian region Lying essentially east of the Urals, this is a region with few native flowering plants. Those that do exist belong mainly to the Cruciferae family, such as Borodinia and Macropodium. A few important garden species, however, are native here, such as Bergenia species, Iris sibirica, Allium sibiricum, and Delphinium grandiflorum.

Northern forests The main vegetation formation is that of the boreal coniferous forest, which is much richer in species than its European counterpart, with the spruce Picea obovata, Abies sibirica, larch Larix sibirica, and pine Pinus sibirica. The spruce element in the forest declines towards the east until, in the continental parts of eastern Siberia, it is entirely absent. Similarly, the larch Larix sibirica fades out, to be replaced by other larch species such as Larix dahurica. Larch forests occupy about 2 million sq km in Siberia.

The mountains of northeastern Asia These harbour an interesting Alpine flora. The Altai Mountains, for example, possess an Alpine flora of some 300 species, in which the Arctic-Alpine element is about 60%. North of the boreal coniferous forests are the dwarf-shrub and forest tundra and the tundra proper.

The Sino-Japanese region This region, with a mosaic of deciduous woodlands, moist warm temperate forests, and mountain vegetation, possesses the richest flora in the whole of the north temperate zone. The main reason for this is probably that the flora was far less affected by the Pleistocene ice ages than its counterparts in Europe and North America.

This region has been the source of a great many plants now well known to gardeners all over the world. Widespread in the region are Clematis montana and Rosa rugosa; more exclusively in China and Japan are found Aucuba japonica, Camellia japonica, Hosta, Hydrangea macrophylla, and possibly the ancestors of our cultivated chrysanthemums. Of species native to China, Jasminum nudiflorum, Kerria japonica, and Wisteria sinensis are famous, while from Japan come plants like Fatsia japonica and Schizophragma hydrangeoides, not to mention the enormous range of Prunus cultivars.

Within the region lies the mountain chain of the Himalayas, again so well known for its contributions to horticulture. Of particular note here is the massing of Rhododendron species in the river-gorge country bordering Burma, India, and China. Over 700 species have been described from the Sino-Himalayan mountain system. Within the Himalayas, there is a very complex pattern of vegetation zonation related to altitude and microclimate. The southern part of the Sino-Japanese region has attracted the attention of theorists interested in the origins of the flowering plants. The type of climate found in Yunnan, for example, has been suggested as that most suitable for the evolution of the angiosperms.

The Western and Central Asiatic region The vegetation of this dry, mountainous desert region is limited. A rather specialized area, however, is the cold Tibetan plateau. This is the largest highland area in the world, some 2,000 km from east to west and with an average height of 4,500 m above sea-level. Its vegetation is varied: in deeply incised southern valleys there are Himalayan forest elements; swampy areas, with frost-shattered material, support Kobresia tibetica. Then there are desert habitats with dwarf shrubs, salt lakes, and even sand dunes. The grass Poa altaica has been recorded from an altitude of around 6,000 m/19,680 ft.

In the central Asiatic deserts, where annual rainfall is low and comes in spring and summer, the flora consists of shrubby plants adapted to sandy habitats, such as Artemisia species, grasses, especially Stipa species, plants adapted to salty conditions, and a few trees close to streams and rivers, like Ulmus pumila. Like other deserts, the region also has a wide range of ephemeral plants that respond quickly to the spring rains. Sandy deserts have a number of characteristic shrubs, such as the white saxaul (Haloxylon persicum) and the black saxaul (H. aphyllum). Many valuable plants have come from northern Iran and the interior of Asia Minor, including Fritillaria imperialis, Jasminum officinale, Philadelphus coronarius, and Platanus orientalis, the tree that helped to produce the hybrid P. × hispanica, the London plane, which grows so successfully in the polluted atmospheres of European cities.

The Indo-Malaysian region The lowland tropical rainforests of peninsular and island Southeast Asia are some of the most complex vegetation formations in the world. The area as a whole is exceedingly rich in flora, with over 25,000 species of flowering plants, and about 10% of the world's flora. Peninsular Malaysia and Singapore alone possess about 7,900 species and 1,500 genera of seed plants. Some 40% of the area's genera are endemic. The orchid family (Orchidaceae) is the largest, with up to 4,000 species, while some 500 species of the essentially Southeast Asian family, Dipterocarpaceae, are the main forest constituents. One of the world's most famous rainforest plants, the parasitic Rafflesia arnoldi, comes from Sumatra. The vegetative part of the plant is reduced to cellular threads penetrating the roots of the host plant, while the bright red-brown flower reaches a diameter of 1 m/3 ft and smells like rotting meat, thus attracting the flies that pollinate it.

The Malaysian region is also the home of the two wild banana species, Musa balbisiana and Musa acuminata, which are thought to be the source of nearly all the cultivated forms. On the landward margins of the mangrove swamps, forming a low brackish water association, is the distinctive Southeast Asian palm, Nypa fruticans, the leaves of which are widely used for thatching.

Timber The monsoon forests of India and Southeast Asia are renowned for the production of one of the world's finest timbers, teak (Tectona grandis, family Verbenaceae). The teak tree is an important constituent of the tropical moist deciduous forests of India, Burma, Thailand, Laos, Cambodia, and Java. In 1969, the teak forests and plantations of east and central Java covered some 700,000 ha and yielded 546,000 m3 of timber – over 90% of the timber produced. Where the dry season is long, savannah forests predominate. Particularly famous are the sal forests (Shorea robusta) of northern India; these trees are the most commercially important in tropical Asia, yielding not only timber but also a dye manufactured from the bark, vegetable oil, incense, and edible nuts.