Phyllostegia Knudsenii

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Phyllostegia knudsenii

No Common Name

ListedOctober 10, 1996
FamilyLamiaceae (Mint)
DescriptionErect perennial herb or vine; bears flowers in groups of two or four and fruits, which are four black fleshy nutlets.
Habitat'Ohi'a lowland mesic forest at 2,840 ft (866 m) elevation.
ThreatsHabitat degradation by pigs and goats; competition with alien plant species.


Phyllostegia knudsenii is an erect, perennial herb or vine of the mint family (Lamiaceae). The opposite leaves are limp, ovate, faintly pubescent, 4.5-7 in (11.4-17.8 cm) long, and 2-3.5 in (5-8.9 cm) wide. Flowers are borne in groups of two to four along a flower stalk 1.6-2.6 in (4-6.6 cm) long. The corolla is 0.2-0.3 in (0.5-0.75 cm) long. The fruits are four black fleshy nutlets in each flower and are 0.06-0.8 in (0.1-2 cm) long. This species differs from others in this genus in its specialized flower stalk. It differs from the closely related P. floribunda in often having four flowers per group.


P. knudsenii is found in 'ohi'a lowland mesic forest at an elevation of 2,840 ft (866 m). Associated species include olomea, Cyrtandra kauaiensis (ulunahele), C. paludosa (moa), Elaeocarpus bifidus (kalia), Cryptocarya mannii (holio), Doodia kunthiana, Selaginella arbuscula, lama, Zanthoxylum dipetalum (a'e), Pittosporum sp. (ho'awa), Pouteria sandwicensis ('ala'a), and Pritchardia minor (loulu).


P. knudsenii was only known from the type collection made in the woods of Waimea in the 1800s until 1993, when botanists at the National Tropical Botanical Garden rediscovered one individual of this species in Koaie Canyon. Two individuals in the same area have been found since then.


Major threats to P. knudsenii include habitat degradation by pigs and goats; competition with alien plant species such as pipili, Hilo grass, lantana, and air plant; and a risk of extinction from naturally occurring events and reduced reproductive vigor due to the small number of individuals in the only known population. Unrestricted collecting for scientific or horticultural purposes and excessive visits by individuals interested in seeing rare plants are potentially severe threats to P. knudsenii, which has only one population of fewer than five individuals. Collection of whole plants or reproductive parts of the plants could damage the gene pool and threaten the survival of the species. Drymaria cordata (pipili)a pantropical annual herb naturalized in shaded, moist sites on Kauai and four other islandsis also a threat, as are air plant, Hilo grass and lantana. Erosion, landslides, and rock slides are especially dangerous threats to the only population of P. knudsenii.

Conservation and Recovery

A single seed was in storage at the National Tropical Botanical Garden in 1997; the same year, fencing was constructed around the three known plants by the State of Hawaii's Department of Forestry and Wildlife. In order to prevent P. knudsenii from going extinct, propagation efforts and the maintenance of adequate cultivated genetic stock should be continued. Additional wild seeds should be collected periodically until the cryopreservation method of long-term storage is perfected. Emergency measures should be taken immediately to fence the remaining individual to protect it against further degradation by feral pigs.


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


U.S. Fish and Wildlife Service. 1988. "Kauai II: Addendum to the Recovery Plan for the Kauai Plant Cluster." U.S. Fish and Wildlife Service, Portland, Oregon. 84+ pp.