Vanda

Vanda, abbreviated in the horticultural trade as V.,^[2] is a genus in the orchid family, Orchidaceae. There are about 87 species,^[3] and the genus is commonly cultivated for the marketplace. This genus and its allies are considered to be among the most specifically adapted of all orchids within the Orchidaceae. The genus is highly prized in horticulture for its showy, fragrant, long-lasting, and intensely colorful flowers.^[4] Vanda species are widespread across East Asia, Southeast Asia, and New Guinea, with a few species extending into Queensland and some of the islands of the western Pacific.^[1][5]

Etymology

The name "Vanda" is derived from the Sanskrit (वन्दाका)^[6] name for the species Vanda roxburghii (a synonym of Vanda tessellata).^[7][8]

Distribution

These mostly epiphytic, but sometimes lithophytic or terrestrial orchids, are distributed in India, Himalaya, Southeast Asia, Indonesia, the Philippines, New Guinea, southern China, and northern Australia.

Description

The genus has a monopodial growth habit with flat, typically broad, ovoid leaves (strap-leaves). Species with cylindrical (terete), fleshy leaves, which are adapted to dry periods were transferred to the genus Papilionanthe. The stems of these orchids vary considerably in size; some are miniature plants and some have a length of several meters. The plants can become quite massive in habitat and in cultivation, and epiphytic species possess very large, rambling aerial root systems. The roots have pneumatodes.^[9]

The few to many flattened flowers grow on a lateral inflorescence. Most show a yellow-brown color with brown markings, but they also appear in white, green, orange, red, and burgundy shades. The lip has a small spur. Vanda species usually bloom every few months and the flowers last for two to three weeks.

Ecology

Pollination

Vanda falcata has been reported to be pollinated by several hawkmoth species of the genus Theretra, namely Theretra japonica and Theretra nessus.^[10]

Conservation

Many Vanda orchids (especially V. coerulea) are endangered, and have never been common because they are usually only infrequently encountered in habitat and grow only in disturbed forest areas with high light levels, and are severely threatened and vulnerable to habitat destruction.^[4] The export of wild-collected specimens of the blue orchid (V. coerulea) and other wild Vanda species is prohibited worldwide, as all orchids are listed on Appendix II of the Convention on International Trade in Endangered Species.

Cultivation

This genus is one of the five most horticulturally important orchid genera, because it has some of the most magnificent flowers to be found in the orchid family. This has contributed much to the work of hybridists producing flowers for the cut flower market. V. coerulea is one of the few botanical orchids which can produce varieties with blue flowers (actually a very bluish purple), a property much appreciated for producing interspecific and intergeneric hybrids.

The color blue is rare among orchids, and only Thelymitra crinita, a terrestrial species from Australia, produces flowers that are truly "blue" among the orchids, the other being Aganisia cyanea, a lowland species from northern South America that is difficult to cultivate, but has metallic blue flowers. Both of these species, much like Vanda, also have a bluish-purple tint towards the inner petals of the flowers.

Vanda dearei is one of the chief sources of yellow color in Vanda hybrids.

The plants do not possess pseudobulbs, but do possess leathery, drought-resistant leaves. Almost all of the species in this genus are very large epiphytes found in disturbed areas in habitat and prefer very high light levels, the plants having large root systems. Some of these species have a monopodial vine-like growth habit, and the plants can quickly become quite massive.

These plants prefer consistent conditions day-to-day in cultivation to avoid dropping their bottom leaves. The epiphytic species are best accommodated in large wooden baskets, bare rooted, which allows for the large aerial root systems. Disturbing or damaging the roots of large, mature vandaceous orchid plants, and in particular, Vanda and Aerides species, can result in the plants failing to flower and going into decline for a season or more. These plants do not tolerate disturbance or damage of their root systems in cultivation when they become mature. The terete-leaved terrestrial species are very easy to cultivate.

When grown bare-rooted, the epiphytic species require daily watering and weekly feeding and are very heavy feeders in cultivation. They can be grown out-of-doors in Hawaii and the like provided they are given some shade.

Fungal infections

Cross section of Vanda stem infected with Fusarium, exhibiting typical purple spotting of vascular tissue

Unfortunately fungal infections are not uncommon in cultivated plants. A variety of phytopathogens may infect Vanda orchids. Vandas may be affected by Fusarium wilt. This disease is characterized by purple discolouration in the vascular tissue, which results in the loss of their function. The hyphae and spores block the conductor vessels. Affected plants may superficially appear healthy, as they continue to grow, the oldest parts of the plants can be affected and the disease will eventually progress throughout the entire plant.^[11] If cutting tools are not sterilized the infection may spread to other plants.^[12]

Systematics

In a recent molecular study of the genus Vanda ,^[13] several Genera including the former Genus Ascocentrum, Neofinetia and Euanthe were brought into synonym with Vanda.^[1]

Species

The following is a list of Vanda species recognised by Plants of the World Online as of January 2023:^[1]

Vanda ampullacea

Vanda Robert's Delight

Vanda tricolor

Vanda falcata

Vanda hindsii by Lewis Roberts

Vanda lamellata

Vanda garayi

Natural hybrids

• Vanda × boumaniae (V. insignis × V. limbata) (Lesser Sunda Is.)
• Vanda × charlesworthii (V. bensonii × V. coerulea) (Myanmar)
• Vanda × confusa (V. coerulescens × V. lilacina) (Myanmar)
• Vanda × hebraica (V. denisoniana × V. brunnea) (Myanmar)^[14]

Intergeneric hybrids

Vanda Pachara Delight

Vanda Robert's Delight 'Crownfox Magic'

Vanda Sansai Blue

The following is a list of hybrid genera (nothogenera) in which hybrids vandas with orchids of other genera are placed although many of these are invalid because of recent taxonomic changes. For instance, × Ascocenda (Ascocentrum x Vanda) and × Vandofinetia (Vanda x Neofinetia) are no longer valid because both Ascocentrum and Neofinetia have been reduced to synonyms of Vanda by RHS, which is in charge of the International Orchid Register:

References