Trematolobelia Singularis

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Trematolobelia singularis

No Common Name

ListedOctober 10, 1996
FamilyCampanulaceae (Bellflower)
DescriptionUnbranched shrub with long and narrow leaves and violet petals.
HabitatSteep, windswept cliff faces or slopes in 'ohi'a-uluhe lowland wet shrubland.
ThreatsHabitat degradation by feral pigs, potential predation by rats, competition with the aggressive alien plant Koster's curse.


Trematolobelia singularis, an unbranched shrub of the bellflower family, has stems 2-5 ft (0.6-1.5 m) long. The long and narrow leaves are 4-7 in (10-18 cm) long and 0.4-0.7 in (1.0-1.8 cm) wide. The un-branched, erect flowering stalk is 8-16.5 in (20-42 cm) long. The violet petals are about 0.2 in (0.5 cm) long and collectively form a three-lobed tube; the largest lobe is curved downward, while the other two are bent backward, giving the appearance of two lips. The capsules are almost round and contain numerous small, wind-dispersed seeds. This species differs from others of this genus by the un-branched, erect flowering stalk.

Harold St. John described Trematolobelia singularis in 1982 from a specimen collected by John Obata in 1974. This species has been maintained in the most recent treatment of this endemic Hawaiian genus. The specific epithet refers to the solitary flowering stalk.


T. singularisusually grows at elevations from 2,300-3,150 ft (701-960 m) on steep, windswept cliff faces or slopes in 'ohi'a-uluhe lowland wet shrub-land. Associated plant species include 'akia, hapu'u, kanawao, and na'ena'e pua melemele.


T. singularis has been reported only from the southern Koolau Mountains. Approximately 165 plants were known in 1997 from three populations found on private, City and County of Honolulu, state, and Federal lands50 plants occurred at Moanalua-Tripler Ridge summit to Puu Keahiakahoe, 40 at Konahuanui, and 75 at Puu Lanipo.


The most serious threats to T. singularis are habitat degradation by feral pigs, potential predation by rats, competition with the aggressive alien plant Koster's curse, and risk of extinction from random natural events and through reduced reproductive vigor due to the small number of extant populations.

T. singularis is potentially threatened by feral pig predation because the plant is not known to be unpalatable to pigs and they favor plants from the bell-flower family for food. It is possible that rats eat the fruit of T. singularis.

The noxious shrub Koster's curse is also a threat to this species.

Conservation and Recovery

The known habitat of the T. singularis is on land owned by the City and County of Honolulu, the State of Hawaii, and the Federal Government (Omega Coast Guard Station). These publicly owned habitats should be protected from degrading influences, and managed to reduce the impacts of introduced mammalian herbivores and alien plants. Some habitat is on private land, and should also be protected. This could be done by acquiring the habitat and establishing ecological reserves, or by negotiating conservation easements with the landowners. The populations of the T. singularis should be monitored, and studies made of its habitat needs.


U. S. Fish and Wildlife Service
Pacific Islands Ecoregion
300 Ala Moana Boulevard, Room 3-122
P.O. Box 5088
Honolulu, Hawaii 96850.
Telephone: (808) 541-3441
Fax: (808) 541-3470

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Building
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
(503) 231-6121


U.S. Fish and Wildlife Service. 10 October 1996. "Endangered and Threatened Wildlife and Plants; Determination of Endangered Status for Twenty-five Plant Species From the Island of Oahu, Hawaii." Federal Register 61(198): 53089-53108.