The Flowering Plants of Hawaii
Part 45 Sapindaceae-Sapotaceae-Scrophulariaceae
The Sapindaceae, the soapberry family, are a family of the tropics and subtropics that consist of 1,450 species in 131 genera (Mabberley, p.766) now considered to include genera that were at one time members of other families: Acer, the maples (Aceraceae) and Aesculus, the horse chestnuts (Hippocastanaceae). More familiar genera to readers who enjoy tropical fruits are Nephelium lappaceum, the rambutan, and Litchi chinensis, the lychee nut. Although some of these fruits are grown in the Hawaiian Islands, they have not become naturalized to the best of my knowledge.
The most readily identifiable member of Sapindaceae in the islands is Dodonaea viscosa (see image), known by several names in Hawaiian including `a`ali`i, `a`ali`i kü makani, `a`ali`i kü ma kua, and kümakani. This species is easily recognizable by its often brightly colored, winged fruits, which are popular for lei making. `A`ali`i occurs over a wide range of habitats and on all of the main islands except Kaho`olawe. The species is pantropical in distribution and extremely variable. A large variant of this species—and there apparently are many throughout its range—can be seen in the Hosmer Grove (Haleakalä area) that carries the name D. eriocarpa. (see image). This name is included in the list of synonyms of D. viscosa given by authors of the Manual.
The genus Dodonaea is predominantly Australian where 59 of the approximately 70 species occur as endemics. By comparison, D. viscosa occurs on all continents (except Antarctica) and can be found in a variety of habitats. A recent study of DNA sequences of a wide selection of specimens of D. viscosa by Mark Harrington and Paul Gadek of James Cook University (2009) revealed that the genus is of comparatively recent origin, perhaps as recent as 2 million years, in contrast to earlier opinion, based on its extremely wide range of distribution, that it is an old group. The genus arose in Australia and spread throughout the world by flotation, with dispersal to inland sites assisted by animals. The five specimens from the Hawaiian Islands emerged from the analysis as a single, homogeneous group suggesting that the species on the islands resulted from a single colonization event.
The type genus for the family, Sapindus, has two of its dozen species in the Hawaiian Islands. Sapindus saponaria, a`e or mänele, is a widespread species that occurs on other Pacific Islands as well as in Mexico and South America, and Africa. This species occurs only on the Big Island. The endemic species S. oahuensis (see images), known in Hawaiian as lonomea (in Kaua`i), äulu, or kaulu, is limited in occurrence to northwestern Kaua`i and the two mountain ranges on O`ahu. Seeds of a`e were used in lei making, those of S. oahuensis in lei making and in some medicinal preparations. Sapindus saponaria (see images), a`e or mänele in Hawaiian, is an indigenous species with a distribution that includes Mexico, South America, islands in the Pacific Basin, New Caledonia, and parts of Africa. It is limited in its Hawaiian distribution to Kilauea, Hualälai, and Mauna Loa. The specimen seen here was found growing beside the Mauna Loa Access Road a few miles beyond the Bird Park.
Alectryon is a genus of about 25 species with a range of distribution that includes Australia, New Zealand, Malesia, and islands in the Pacific Basin. A single endemic species occurs in the Hawaiian Islands considered by most authorities to consist of two varieties. Alectryon macrococcus var. auwahiensis (see image), occurs on East Maui, whereas var. micrococcus (see image) can be found on Kaua`i, Moloka`i, O`ahu and West Maui. The species is known as mähoe or `ala`alahua in Hawaiian. The authors of the Manual suggest that the reason the hard wood of this tree was not used was rarity of the species, in contrast to the routine use of other hard wood species.
The numbers of genera and species according to the two authorities here are 53 and 975 (Mabberley p. 767), and 60 and 900 (Manual). The family is mostly found in the humid tropics with a few temperate representatives. The Hawaiian Islands are home to two species, one in each of two genera. Nesoluma polynesicum (Nesoluma.jpg, Nesoluma1.jpg), known locally as keahi, occurs on Raivavavae (one of the Austral Islands) and Rapa (sometimes considered one of the Australs, but is of independent origin geographically and culturally), and on the Hawaiian Islands. It was once more common in dry forests but is now considered rare. These photographs were taken in the Maui Nui Botanical Garden.
The other genus, Pouteria, is represented on the islands by one endemic species, P. sandwicensis (see image), widely known in Hawaiian as `äla`a, but also as äulu, `ëla`a, or kaulu. The photograph was taken in the dry forest on western Läna`i. The tree can easily be recognized by the rust-colored hairs on the undersides of its leaves. The milky sap of this tree was used to capture birds; its hard wood was used to make `ö`ö (digging sticks) and spears.
Likely the most well known member of the Scrophulariaceae, especially to North American gardeners, would be Antirrhinum, the snapdragon. Other common members will be recognized below. The family has undergone massive re-adjustment in recent years based on gene sequence data. These changes involve at least two of the genera represented on the islands, Bacopa and Castilleja, but other than noting their new family alignment, we will stay with the family placement as in the Manual.
The Indian paintbrush, taken in the broadest meaning of the name, is one of the most significant suppliers of color to the western landscape. There are about 190 species of Castilleja, the majority of which are North American with others known in Central and South America. The Hawaiian species, C. arvensis (see image), occurs naturally in Mexico and south to Brazil and Peru. The plant in the photograph was one in a small patch growing beside the Kuilau Trail on Kaua`i in otherwise disturbed soil. I have also seen it beside the Boy Scout Trail on East Maui. One further note on Castilleja: recent DNA-based research puts it, along with other hemiparasitic genera, in the Orobanchaceae. Other genera of Scrophulariaceae represented on the islands include Bacopa (see image), Lindernia (see image) and the attractive plant (Scroph.unknown.jpg) for which I have not found the correct name.
The major, and most troublesome member of the family by far is the common or woolly mullein Verbascum thapsus (see images). Other names for this plant are Aaron’s rod, the flannel plant, and hog taper. It is a comparative newcomer to the islands but it has made its presence known.
Mullein is a very aggressive weed easily occupying large areas of marginal or disturbed ground. Once this plant becomes established it is extremely difficult to remove, especially considering its very long lived seeds—100-year old seeds have been shown to be viable! One of the most spectacular showing of this alien is on the southern flank of Mauna Kea in the area around Hale Pöhaku, the Onazuka Astronomical Center information office.
The team of Sandra and James Juvik, likely best known to non-scientists as the editors of the Atlas of Hawai`i, have written on various subjects in Hawaiian plant biology including a study in 1992 of the spread of mullein on the Big Island. The following information is abstracted from that report. Mullein is native to temperate regions of Eurasia but has become naturalized worldwide primarily in disturbed areas, and has become a pest in many places. It has wide ecological tolerance and is quite at home on marginal substrates. Once established in an area it can be difficult to remove completely owing to its seeds’ very long term stability in soil, shown to be as much as a century.
Mullein was introduced to the Island of Hawai`i in the early years of the 20th century in the Kona District (west side) and had reached the summit area of Hualälai by 1932 where it attained the status of dominant plant species by 1946. A few years later its presence in the Saddle Area between Mauna Loa and Mauna Kea was recorded. Over the next twenty years or so mullein became well established high on the slopes of Mauna Kea predominantly along the access road. Since mullein has no special adaptive feature for long distance dispersal—the majority of fruits fall within a few meters of parent plants—it has obviously been transported by human activity, most likely in tire mud.
The issue of movement of invasive plants by vehicle tires was addressed by Christopher Dacus and coworkers (2009), speaking for the Hawai`i Department of Transport (HODT) at a recent conference. HODT has instituted a statewide program of removal of noxious and invasive plants from roadsides—the program is called SNIPP which stands for Statewide Noxious/Invasive Plant Project. Their program, which has received funding for three years involves, in addition to developing policy, clearing major roadways of invasive plants and reseeding with native species. Efforts will also be made to prepare an Integrated Roadside Vegetation Manual that will provide guidelines for road workers and any other groups who might wish to become involved.
It is ironic that the area occupied by mullein on the upper slopes of the mountain closely parallels the original habitat of the Mauna Kea silversword, an example of a phenomenon referred to as niche replacement. Replacement of the beautiful silversword by ugly mullein is an insult to Nature! I have even seen picture postcards featuring the mullein on Mauna Kea.
The situation on Mauna Loa is, unfortunately, similar, with significant infestation between 1,500 and 2,100 m elevation in the northwestern section of Hawai`i Volcanoes National Park paralleling the Mauna Loa Strip Road. Mullein was first reported from the area in the early 1970s but is likely to have been there longer, possibly brought to the area on a truck or car tire. During the period 1994-1999 mullein was monitored in this area by Rhoda Loh and coworkers (2000) who determined that it was present on 1,003 hectares (ca. 2480 acres) between 1,500 and 2,100 m elevation. Densities in the range of 1,400 individuals per hectare (2.47 acres) were observed on weathered `a`ä lava flows that lay adjacent to vegetated kipukas, while the lowest density occurred on open lava fields. Removal of mullein by uprooting is possible owing to the shallow root system, but cleared areas must be revisited annually to monitor new growth.