Part 60 Orchidaceae
There is something especially appealing about orchids to most folks. They seem to evoke a sense of tropical splendor, with their exotic floral designs and array of spectacular colors, true marvels of nature. Something this exotic must be rare! It comes as a surprise to many then that Orchidaceae are a very large family of flowering plants–22,500 species in 779 genera according to Mabberley (p. 606-608)–second only to Asteraceae. The Hawaiian contribution to the orchid numbers in terms of endemic island species is very small. There are only three endemic orchids on the archipelago, one each in three genera: Anoectochilus, the jewel orchids; Liparis, the twayblades; and Platanthera, the fringed orchids.
With its tropical climate and lush vegetation the casual observer could be excused in wondering why there are so few native orchids in the islands, especially considering how well represented several other smaller families are. Calling Hawai`i the Orchid Isle doesn't help matters; the name arises, not from the variety of orchids that occur naturally on the island, but rather from the success of commercial orchid growers on the island, and the very popular cultivation of orchids in hobby gardens. Why, then, are the Hawaiian Islands so poorly represented by endemic orchids? Let's look at the requirements for successful colonization of an island: (1) a propagule must make it to the island alive; (2) it must land in a suitable habitat; (3) successful germination or root establishment is crucial; and (4) the resulting plant must reproduce successfully, which may depend on availability of pollinators in the new setting.
Getting to the islands alive, as stipulated in requirement (1), is noteworthy in the case of orchids because their seeds are among the smallest among flowering plants and consist of a three-cell embryo enclosed in a very thin casing, all of which results in a package that is little more than a speck of dust. This size enables them to be carried great distances by even the slightest air current. The problem arises when the tiny packages are lifted to altitudes where they would be subjected to cold temperatures and strong ultraviolet radiation, either of which is deadly to the immature embryo. Without dismissing requirements (2) and (3) as unimportant, requirement (4) can present a special problem for orchids. Plant pollinators can be lumped into two general groups, generalists, where flower structure is not a constraint, and specialists, where flower structure dictates, often to a great extent, what insects can act as pollinators. Orchids belong to the latter group where the shape and size of the flower dictates which insects, usually bees, can fit into the floral tube and thus bring about pollen transfer. It is theoretically possible that some orchid colonists did succeed in getting to the islands at one time but, lacking specific pollinators, failed to survive.
Anoectochilus sandvicensis (see image), a Hawaiian endemic species, occurs in shady forests on wet moss-covered ground. It is one of about 30 species from tropical Asia, Japan, and some Pacific Islands. It occurs on all of the main islands except Ni`ihau and Kaho`olawe, neither of which has suitable wet habitats. Orchid fanciers would also recognize the common name jewel orchids for this genus.
Four genera of naturalized orchids are listed in the Manual, each represented by a single species. The first of these that we will look at is Arundina graminifolia (see image), the common bamboo orchid. The specific epithet of this species 'graminifolia' informs us that its leaves are grass-like. It is this feature and its capacity to grow to heights of five or six feet (Mabberley, p. 71, says up to 3m) that allows the bamboo orchid to be seen easily as it stands above most of the grass in which it commonly grows. There is only the one species in the genus with a natural range extending from the Himalayas to the Pacific. It is comparatively easy to cultivate this attractive species, which may help to explain its widespread distribution on the Hawaiian Islands.
The genus Phaius consists of as many as 30 species with a distribution that includes Indomalaysia, China, Africa, Australia, and New Caledonia. Phaius tankarvilleae (see image), commonly called the Chinese ground or nun's orchid, occurs from the Himalayas to Australia. It is a widely cultivated ornamental that has escaped in the Hawaiian Islands and has become naturalized at least on Kauai, O`ahu, Läna`i, and on the Big Island. The photograph was taken on Waihe`e Ridge on Maui.
Our next example is the Malayan or Philippine ground orchid Spathoglottis plicata (see image) one of 53 species with a range that includes tropical Asia and Australia, Samoa and Niue. The high atoll island Niue lies about 1,490 miles (ca. 2,400 km) northeast of New Zealand.
The moderately large genus Platanthera consists of about 200 species with centers of diversity in Eastern Asia and North America (Mabberley, p. 676). It is represented in the Hawaiian Islands by the rare P. holochila (see image). This fringed orchid is known from all of the main islands except Hawai`i, Ni`ihau, and Kaho`olawe, but it is nowhere common. I was fortunate to find it in dark forest beside the trail near the Pëpë`öpae Bog on Moloka`i.
Our last example of an endemic Hawaiian orchid is Liparis hawaiensis (see image), `awapuhiakanaloa in Hawaiian. This moderately large genus of some 250 species enjoys a nearly cosmopolitan distribution, but is not known in New Zealand. The Hawaiian name for this plant is interesting as it says this species is the 'ginger of Kanaloa.' Kanaloa was one of the four major gods of the Hawaiians. I do not know how the god and the plant became linked.
Orchid culture is a favorite pastime for many of the islands' inhabitants ranging from a few plants on a window sill to more elaborate collections such as very large collections as exemplified by the garden (image) on the grounds of the Kiahuna Plantation Resort in Po`ipü, Kaua`i.
February 3, 2013