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Rare Delights in Hawai‘i
title graphic

by Bruce A. Bohm

Maui
Photo 5 - Southern coast of Maui, see under Capparis in text.
When talking about plants, the word “rare” is too often associated with the word “endangered.” Unfortunately, this is all too often the case with rare plants of the Hawaiian Islands. Plants of any given group-species, genus, even family-are necessarily limited on islands owing simply to the fact that most islands are comparatively small. This is no less the case in the Hawaiian Islands where, for example, Hawaii Island (familiarly, the Big Island) can be driven around in a long day, and it exceeds in area all of the others together. Other than the obvious limitation of space, there are several reasons why some species are scarce: they were never very abundant in the first place; they are nearing the end of their natural existence, the decline having been caused by some natural phenomenon; and their habitat has come under attack by humans. In light of the overwhelming urge (I won’t say need) to cover every square yard of land with some profitable attraction, humans have destroyed habitats that provided the unique requirements needed for the maintenance of island endemic species. We can do nothing for the ones that are gone. But for the ones that remain, there is some hope. Through the work of committed organizations-both public and private-efforts are being made to protect the islands' rare plants and the habitats in which they occur. Some of the efforts to save the silverswords were mentioned in an earlier article on this site Silverswords-Flagship Plants of Hawai‘i. Extensive field exploration has either confirmed the scarcity of a species (it's not possible to prove an absence) or turned up new populations of otherwise known rare species. Seeds, or occasionally living plants, are brought back to established nurseries where efforts are made to bring the rare species under cultivation. If cultivation proves successful, a program of returning these 'survivors' to their natural habitat may be undertaken.

The locations of nurseries and out-planted sites are not generally advertised for security concerns-I know of only a few. Several of the rare plants described below, however, can be found in botanical gardens open to the general public. When visiting the islands visitors should plan to include stops at the Lyon Arboretum in Honolulu; the McBryde Garden on Kaua‘i's south coast, home to the largest collection of Hawaiian plants in cultivation-referred to as a “botanical arc”; the Limahuli Garden on Kaua‘i's north coast, which specializes in endemic species of Kaua‘i; and the small, but botanically very interesting, Maui Nui Botanical Garden in Kahului, Maui.

The plants featured below represent only a sampling of the rare (and endangered) plant species on the Hawaiian Islands. They are presented in alphabetical order.

Binghamia
Photo 1 - Brighamia insignis
Binghamia
Photo 2 - Brighamia insignis
Binghamia
Photo 3 - Mature Brighamia insignis
Brighamia (Campanulaceae), with its two species, would certainly qualify as one of the Plant Kingdom's real cliff-hangers, both in terms of where it lives and its dicey future. The present ranges of the two species are the steep north-facing cliffs of Kaua‘i, in the case of B. insignis; and Moloka‘i in the case of B. rockii. The two are very similar differing mainly in flower color and location; both species are considered endangered. Efforts to hand pollinate these plants has been moderately successful; both appear to grow well in garden settings. Brighamia insignis in a nursery setting at Kilauea Point on the northeastern coast of Kaua‘i (site of the Kilauea Lighthouse) is shown in Photos 1 and 2. Older plants can reach heights of up to ca. 15 ft (ca. 5 m) and are characterized by a stout stem swollen at the base. Leaves radiate from the top of the column; flowers are white and have an attractive scent. The Hawaiian name for B. rockii is pua ‘ala (literally, fragrant flower), while the names for B. insignis, ‘ölulu and pü aupaka, appear to be specific for that species. Mature specimens can be seen in the Limahuli Botanic Garden where Photo 3 was taken.

Capparis sandwichiana
Photo 4 - Capparis sandwichiana
Capparis sandwichiana
Capparis sandwichiana (Capparaceae) is the only endemic member of this family on the Hawaiian Islands. Readers will be familiar with the caper of culinary use; it is the pickled unopened flower bud of C. spinosa a native of the Mediterranean region. The Hawaiian species is distributed in coastal habitats on all of the main islands. It is categorized as a “vulnerable” species in Hawai‘i, which recognizes the dangers to its habitat presented by development of coastal areas. Photo 4 was taken on the southern coast of Maui near the entrance to the King's Highway, a trail of historical significance that follows the coastline of southern Maui. In order to see this beautiful plant in flower, visitors should plan to reach the site early as the flower quickly fades in the heat of the day. The site is reached by driving south as far as the paved road allows-to La Pérouse Bay-and then hiking along the coast (Photo 5) until the lava flow is reached, about a mile from the parking area at the end of the road.

Delissea rhytidosperma
Photo 6 - Delissea rhytidosperma
Delissea rhytidosperma
Photo 7 - Delissea rhytidosperma
Delissea rhytidosperma
Delissea (Campanulaceae), another of the spectacular lobelia relatives of the Hawaiian Islands, is a genus of nine species, seven of which are extinct. The remaining two-perhaps only one-are D. subcordata, last collected on O‘ahu in 1934, and D. rhytidosperma, a rare Kaua‘i endemic known from only a few sites on the island, and now under cultivation at Limahuli Garden. Photo 6 shows a specimen in an early stage of flowering; Photo 7 shows a plant in full flower with some maturing fruits.

Delissea is not the only genus within the Hawaiian Campanulaceae that has significant members either at risk or gone altogether. Clermontia, for example, is reckoned to consist of 22 species, three of which are rare with one extinct. Cyanea, the next to largest genus in the Hawaiian flora with 52 species listed in the Manual (as of 1999), consists of 22 species that are not at risk, 16 that are rare or endangered, and 14 that are extinct. The genus Trematolobelia, with four species, appears to be relatively well off with only one of its species listed as rare.

An often asked question is: if a species is extinct, how do you know it existed in the first place? Descriptions of many plant species was done by specialists working with dried specimens in museum collections. As seems likely, collectors, not knowing of the rarity of a newly discovered plant, collected every individual they saw. Many of the plants were never very abundant in the first place, and certainly couldn't stand that sort of sampling. Another reason for extinction is the wholesale loss of habitat caused by land clearance for agriculture; harvesting forests for building purposes, which took most understory plants out with them; and massive development of housing and recreational facilities on the islands.

Photo 8 - Haplostachys haplostachya
Haplostachys haplostachya
The Hawaiian Islands are home to one nearly endemic genus and two endemic genera of mints (Lamiaceae = Labiatae): Haplostachys with a single extant species (out of five); Phylostegia, with 27 Hawaiian species (four or five extinct) and one native to Tahiti; and Stenogyne, with 20 species (three or four extinct). Many species in the latter two genera are considered at risk. The only surviving member of Haplostachys, H. haplostachya, honohono in Hawaiian, is the subject here. This species, never very abundant, has been reduced to a single population on Kïpuka kälawamauna on the saddle between Hualälai and Mauna Kea on the Big Island. The name can be divided a bit to show its origin: a “kïpuka” is, among other things, a vegetated island surrounded by lava. The terminal unit “mauna” is the word for mountain; “kälawa” is likely a place name, although there could be a significance of which I am not aware. Access to this area is prohibited except to authorized individuals (one of which I am not). The plant illustrated in Photo 8 was photographed at the McBryde Garden, which is the showcase garden of the National Tropical Botanical Garden (a.k.a. NTBG). Efforts to propagate this species are being made at the rare plant nursery on the Big Island.

Kanaloa kahoolawensis
Photo 9 - Kanaloa kahoolawensis
Kanaloa kahoolawensis
Photo 10 - Kanaloa kahoolawensis is Kananoa kahoolawensis shrub growing in MacBryde Garden
Kanaloa
Kanaloa kahoolawensis is, with little fear of argument, the rarest of the rare. By one report, we learn that there is a single plant surviving in Nature; by another, two. We won't quibble; suffice it to say that this species is within one or two plants from extinction in the wild. It is growing well in the collection at the McBryde Garden but its future seems nonetheless in doubt. Although the plant grows well in captivity (Photo 9) and produces flowers (Photo 10), it fails to set seeds because it is self incompatible; it needs a partner! Theoretically, there is the possibility of producing more individuals using sterile culture techniques, but these plants, which would all be derived from the same parent and hence possess the identical genetic makeup of that parent, would also be self incompatible.

Kanaloa kahoolawensis is a newly described genus and species of the Fabaceae (Leguminosae)-it was discovered in 1992. It only occurs on nearly inaccessible sea-stacks on the coast of Kaho‘olawe. Its discovery by botanists from the NTBG represented not only a new species but a new genus, a fairly rare find considering the intense level of field activity in the islands for over 250 years. The genus name derives from the Hawaiian name for the island, while the specific epithet comes from the map name of the island. Kanaloa, among other definitions, relates to a major Hawaiian god. The Hawaiian common name for the plant is “Ka palupalu o Kanaloa,” which translates as: the gentleness of Kanaloa.

Although Kanaloa is limited to one or two individuals in the wild, there is evidence that it was more widespread at one time. Pollen discovered in cores taken on O‘ahu, Maui, and Kaua‘i were recognized as originating from an unknown legume. It is now thought that that legume was Kanaloa. The species was co-dominant with Dodonaea viscosa (Sapindaceae) and a Pritchardia sp. (Arecaceae = Palmae) (we'll see both of these in later articles) for a period extending from before 1210 B.C. to 1565 A.D., after which Kanaloa pollen rapidly disappeared, with the other two species declining as well. What caused the plant to disappear remains a mystery: perhaps its habitat came under threat from agricultural activities; perhaps there was a local climate fluctuation. Dodonaea viscosa and several species of Pritchardia remain significant elements in the Hawaiian flora at the present time.

Munroidendron racemosum
Photo 11 - Munroidendron racemosum
Munroidendron racemosum
Photo 12 - Munroidendron racemosum
Munroidendron racemosum
In Munroidendron racemosum (Araliaceae) we meet one of the most elegant of trees. The floral display, a raceme, from which its specific epithet derives, would be an absolute winner were the tree ever to enter the horticultural world. Photos 11 and 12, taken at the Limahuli Garden, show the tree and a close-up of its magnificent floral display. This species is endemic to the nearly inaccessible cliffs of Kaua‘i, and within that area, to only three sites. However, it appears easy to grow, with several very nice specimens available for viewing at the Garden.

Portulaca molokiniensis
Photo 13 - Portulaca molokiniensis
Portulaca molokiniensis
Photo 14 - Portulaca molokiniensis
Portulaca molokiniensis
Portulaca (Portulacaceae) is represented on the Hawaiian Islands by seven species, three naturalized, one indigenous, and three endemic. All of the endemics are considered rare, the one featured here perhaps the rarest of them all. Although first collected in the early part of the 20th century, P. molokiniensis, ‘ihi in Hawaiian, did not receive official recognition as a species until much more recently. Photos 13 and 14 were taken at the McBryde Gardens; it can also be seen in the Maui Nui Botanical Garden. Access to this plant in its natural habitat, the sea bird nesting islet Molokini (a major snorkeling destination) and two small populations on Kaho‘olawe, is limited to authorized visitors. There are likely no more than 1000 individuals known in the wild; the main threat is from alien species. It is thought that it may have evolved from the endemic, and also rare, P. lutea, with which it can cross.

11/9/06



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