The Flowering Plants of Hawaii
Part 42 Rubiaceae
Our next family visit is with the Rubiaceae, the coffee family, one of the largest flowering families in the World with 563 genera and 10,900 species, according to Mabberley (p. 750-752). The numbers in the Manual are 500 and 6,500, respectively. This level of disagreement should not be taken as any indication of competing views, but rather a recognition of the difficulties met in dealing with so large a group of organisms many of which are tropical and not easily studied. The combination of new analytical techniques—primarily DNA sequence comparisons—and refined ideas of what constitutes a "good" genus inevitably lead to changes in overall views of a family. Mabberley pointed out in his family description that, although the family is well defined, generic limits are not so easily established. The generic status of several Hawaiian groups has come under scrutiny in recent years resulting in some changes. These changes do not, however, alter the diversity and biological interest in the species involved.
Again referring to Mabberley's description of the family, the impact of Rubiaceae in terms of contributions to human well being is essentially limited to drugs obtained from some members. Although the nutritive value and therapeutic importance of coffee are debatable, the fact is that it is one of the most widely consumed plant products in the world cannot be questioned. Could the world get along without coffee? Of course it could. Will it? Not likely! Coffee has simply become the most popular non-alcoholic social drink of the present era.
Coffee is made from roasted berries of selected species of the genus Coffea. There are about 100 species in the genus distributed in tropical regions of Africa and Madagascar. Only a few of these species provide beans that lend themselves to the preparation of beverages. The principal one is C. arabica, a native of Ethiopia, but now grown extensively in many tropical countries, including the Hawaiian Islands. Most visitors to the islands have been tempted to sample Kona coffee. Coffee plantations are not limited to the Kona region of Hawai`i, however; there are important commercial growing operations on Kaua`i, Maui, Moloka`i, and O`ahu. Several coffee producers offer tours and shops. When on Kaua`i one should visit the Kaua`i Coffee Company, one of the largest operations on the islands. The Coffees of Hawai`i plantations on Moloka`i (see image), and their shops at Kualapu`u are also worth a visit. More intimate pictures of coffee flowers (see image) and an array of fruits (see image) are provided for readers who, on their visits to the islands, wish to avoid trespass restrictions or have not had the opportunity to visit the National Tropical Botanical Gardens where coffee plants are maintained in the show garden.
Now that we’ve had our cuppa' we can move on to another member of Rubiaceae and its relationship with one of mankind’s scourges, malaria. An exciting episode in the history of the search for pharmaceutically useful plant products involves another genus in Rubiaceae. Quinine is the active principle of certain members of the genus Cinchona that grow at high elevations in Peru. The alkaloids occur in such high concentration in some specimens that crystals of pure quinine can be picked out of crushed bark using tweezers. There have been massive studies to produce synthetic analogues of quinine but the natural occurring compound is still one of the best drugs against stages of the malarial parasite. Much quinine is also used in the manufacture of tonic water which, with the addition of a bit of gin, a squeeze or two of lime, and some ice, becomes the classic gin-and-tonic (G and T), the drink of choice in the tropics. Cinchona pubescens (see image), the only naturalized member of the genus in the Hawaiian Islands, is cultivated for extraction of its quinine, but seems to have become naturalized only on Maui.
Other members of Rubiaceae that readers will recognize would include species of Gardenia, widely planted for their beautiful foliage, large white flowers, and stunning aroma. Other familiar plants belonging to the family are species of Galium, the bedstraws; and madder, Rubia tinctorum, the source of the historically important dye alizarin, also known as rose madder.
The Hawaiian Islands are home to 66 species in 16 genera of Rubiaceae; 52 of the species occur nowhere else on Earth. There is one endemic genus, Bobea, which contributes four species to the flora. Bobea brevipes (see image), `ahakea lau li`i or `akupa in Hawaiian, occurs in mesic to wet forests on Kaua`i and O`ahu. The very durable wood of `ahakea was used for making poi boards (surface for pounding taro), and for paddles and other parts of outrigger canoes. Authors of the Manual tell us that gunwales of modern canoes, often manufactured from fiber glass, are painted yellow to simulate the historic wood. An easy place to see a specimen of Bobea is the short nature walk behind the visitor’s center at Koke`e Park. The diminutive flower of B. elatior is illustrated here (see image).
Coprosma consists of between 90 and 100 species, depending upon authority, with a large percentage of them native to New Zealand, but with species in southern China, the Pacific Basin, South America, and an interesting disjunction to Trista da Cunha in the southern Atlantic Ocean. As currently viewed, there are 13 endemic species on the Hawaiian Islands. One of the easiest species of Coprosma to see in its native habitat, sprawling on open sites on Maui and on the Big Island, is C. ernodeoides, readily recognized by its shiny black berries (see image). A common name for this species is nënë bush, nënë being the endemic Hawaiian goose (image below) (Nesochen sandvicensis); or in Hawaiian as `aiakanënë, meaning food plant of the nënë; or kükaenënë, meaning dung of the nënë; leponënë, also dirt or dung of the nënë; and sometimes simply nënë, which can be confusing unless one knows if the subject of conversation is the bird or the bush. 'Nënë bush' is probably the most common term used by most folks since it avoids the polysyllabic pronunciations that tend to be troublesome for visitors not familiar with Hawaiian pronunciation (which is actually a lot easier than it looks).
A characteristic feature of this species, as with many in the genus, is the existence of male and female flowers on different plants; technically, the species is said to be dioecious. One of the best examples of this phenomenon that I have seen is illustrated here where a female nënë bush plant is seen in full flower (see image). Whereas nënë bush occupies sites at somewhat lower elevations on Hawai`i, our next species of interest grows at higher elevations in the subalpine shrubland. Coprosma montana (see image) is often a major contributor to the vegetation at middle elevations, here at about 7,000’ (2,133 m) on the trail that leads to the summit of Mauna Loa. This species is also dioecious; the flowers seen in the photograph are the pollen bearing male flowers. A contrasting habitat to the dry mountainside of C. montana is wet forest, where one finds C. elliptica (see image). This species was seen growing next to the Pihea Trail hugging the ground or forming low-lying compact shrubs.
Gardenias are probably best known as highly scented decorative plants widely planted because they are comparatively easy to maintain in cultivation. The genus Gardenia consists of about 200 species from tropical and warm habitats in the Old World. In the Hawaiian Islands the most frequently encountered gardenia is the Tahitian gardenia, G. taitensis (see image). the national flower of Tahiti. It is much admired for its simple, large white flowers and attractive aroma, and is widely planted in the Hawaiian Islands, often a favorite for hotel hedges.
There are three species of Gardenia that are endemic on the Hawaiian Islands, all of which are listed as either rare or endangered. The only one of these that I have seen in person is G. brighamii, known as nä`ü or nänü, in Hawaiian. The photograph (see image) of the fruit of this species was taken in the dry forest of western Läna`i. Gardenia manii, restricted to O`ahu, is considered rare and close to extinction (no image). Gardenia remyi (see image) is also rare, although it is known from all islands except Läna`i, Ni`ihau, and Kaho`olawe. The photograph was taken in the Limahuli Valley on Kaua`i.
The largest group of island species in this family belong to the genus Hedyotis. A recent reappraisal of Hedyotis has resulted in its species being transferred (or, rather, returned) to the genus Kadua, which we will follow for the purposes of this series. The genus consists of about 250 species worldwide which are found primarily in tropical and subtropical habitats.
The Hawaiian Islands are home to 22 species, one of which, K. foliosa, is likely extinct since only a few specimens were ever found on Haleakalä. Several species are listed as either rare and/or endangered; the others are moderately abundant. If one wants to see a species of Kadua but wishes to avoid the wettest habitats, K. knudsenii (see image) might be the plant of choice. This species occurs on Kaua`i in the Koke`e area. The specimen shown in the photograph shows the very characteristic floral structure of the genus, although not all species have the tightly clustered array seen here. Kadua centranthoides (see image) can easily be identified by its characteristic flower structure and by its tall, rather leggy growth habit. This species occurs in a variety of habitats including open spaces, edges of bogs, and in mesic forests. I have routinely seen excellent specimens growing beside the service road that parallels the Saddle Road on Hawai`i where the photograph was taken. The colors of the flowers, a combination of pale yellow-green and purple, have to be appreciated on living specimens; dried flowers turn black.
Kadua fosbergii (see image) occurs in the Ko`olau Mountains on O`ahu and on Läna`ihale on Läna`i where the photograph was taken. Note the bright blue fruits of this plant which makes it recognizable in the field from a distance. The next species, K. affinis (see image), was photographed in wet forest on Kaua`i. Identification, although noted as tentative, was provided through the Flickr.com Hawaiian plant identification network. Kadua affinis is not included in the Manual as such, but is the newly assigned name for plants that formerly resided in the highly variable species K. terminalis.
The genus Morinda, with about 90 Old World species, is represented in the Hawaiian Islands by two, the naturalized M. citrifolia (see image), known as Indian mulberry or noni; and the endemic M. trimera, whose Hawaiian name, noni kuahiwi, recognizes that it occurs at higher elevations than noni. Noni was introduced by the Polynesians who used it as a source of medicine and useful dyes. A permanent red dye, called Turkey red, was prepared from bark, while the roots provided a yellow pigment used in dying kapa. Ripe fruit are reported to have been used as a famine food. I have tasted the juice of the fruit; one would have to be very hungry indeed.
The most important use of noni, however, was/is as a source of medicinal preparations, of which there were several. Several applications of noni are described by June Gutmanis (1976) in her compilation of Hawaiian herbal medicine, which should be consulted for details. Purgatives played a significant part in Hawaiian medicine (pp. 24-25 and below) and noni played a part in at least one of these. From that source we learn that juice from young pounded noni was strained, mixed with sugarcane juice and a mashed kukui nut (Aleurites moluccana). This, and other purgative mixtures, induced vomiting as well as acted as a laxative. The noni mixture was considered a 'mild' purgative; more powerful ones employed kukui nuts and preparations made from the bark of the `akoko shrub, species in the genus Chamaesyce, also a member of the Euphorbiaceae. That members of Euphorbiaceae are effective in these remedies should not be surprising to anyone who has had any experience with castor oil, a well known product of Ricinus communis. Hawaiians found that relief from rheumatic joint pain or deep bruises could be had by wrapping the effected area with either noni or kukui leaves applied with heat packs, e.g., hot stones, sand, etc. (p. 26). Noni was also used to treat pimples and boils (p. 30); to induce abortion, although it was not unique in its latter application (p. 33); and to aid in ridding a woman’s body of the afterbirth and retained blood (p. 37). The unsuccessful use of noni fruit preparations in treating Hansen’s disease (leprosy) was related in an apocryphal tale told by Angela Kay Kepler in her 1998 book on Hawaiian Heritage Plants (pp. 145-147).
The very long history of noni ranges from its incorporation into the Indian Ayurvedic system, through its listing as an emergency food for United States servicemen stationed on Pacific Islands during World War II, to widespread claims of its many therapeutic uses in a host of diseases and conditions, to challenges by the Attorneys General of Arizona, California, New Jersey, and Texas against the Utah-based Morinda, Inc. concerning their selling noni as an unapproved drug. It has been a wild ride, to say the least. The full story of noni requires more space than is available here; interested readers should consult the mass of data available on the web and references cited therein.
The widespread tropical genus Psychotria, which consists of some 1,850 species (Mabberley, p. 713), is represented on the Hawaiian Islands by 11, most of which are moderately abundant with at least one species on each island. The floral display with its highly symmetrical branching pattern can be seen in P. mariniana (see image) occurs in mesic to wet forests on all of the main islands except Hawai`i. Examination of the undersides of leaves reveals small dark structures in the axels of the main branching veins (see image). Technically, these are referred to as domatia, from the Latin 'domus' or home. These tiny pockets are frequently occupied by miniscule arthropods of one sort or another.
DNA sequence studies by Molly Nepokroeff of the University of South Dakota and colleagues at the University of Wisconsin and the Smithsonian Institution (2003) showed that Hawaiian Psychotria comprised a monophyletic group (a single lineage) which resulted from a single colonization event. Although it was not possible to pin-point the place of colonization precisely, somewhere on Maui Nui seems the most likely.
The next member of Rubiaceae that we meet here is another genus that has undergone a name change in recent years. Although listed under the older name Canthium—the species of interest is Canthium odoratum—authors of the Manual state in their introduction to the genus that many species of the genus are now housed in Psydrax. In talking about these name changes with a friend on Läna`i, I decided to use the currently accepted name that field workers use routinely, Psydrax odorata (see image). The Hawaiian name for this plant is `alahe`e, which has an interesting origin, as it was described to me. This is a two-part word, the first part, `ala, means sweet smelling, the second, he`e, is the octopus or squid. The sweet scent of this plant—its specific epithet tells us that it is sweet—moves in a wavy motion through the air akin to how the octopus moves through water. This is an indigenous species on the Hawaiian Islands, known otherwise from Micronesia and islands in the South Pacific. The small trees produce a very hard wood that found use in making digging tools ( ö`ö ) and adze blades for cutting softer woods.