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Isodendrion hosakae

Isodendrion hosakae H. St. John

Cindercone Isodendrion

Violaceae (Violet family)


USDA Symbol: ISHO2

USDA Native Status: HI (N)

Rare perennial shrub found only in cinder cones on Hawaii.

"Endemic to an area with a radius of about 2.4 km in the northwestern part of the island of Hawaii. The total number of plants is estimated at about 275 individuals. These are growing on cindercones surrounded by rangeland. Most of the plants have been fenced in order to protect them from grazing cattle. Feral pigs in the area constitute an additional potential threat to the species. An alien, fire-adapted grass has invaded the area and has contributed to an increase in the frequency and intensity of rangefires. In one of these fires, most of the individuals in 1 of the populations were destroyed. Human activities that may have harmed the species in the past include cinder mining and military maneuvers." (Webref: 28). Taxon named in honor of the collector, Edward Yataro Hosaka. (Reslit: 2850).


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Plant Characteristics

Duration: Perennial
Habit: Shrub
Leaf Arrangement: Alternate
Leaf Complexity: Simple
Leaf Shape: Lanceolate
Leaf Pubescence: Villose
Leaf Apex: Acute
Leaf Texture: Leathery
Breeding System: Flowers Bisexual
Inflorescence: Axillary
Size Notes: From 46 to 76 cm in height. (Bibref: 1786).
Leaf: "Twigs leafy for 1- 18 cm., bearing 7- 29 leaves, these spreading and eventually reflexing, rather crowded; upper leafy stems 1-2 .3 mm. in diameter, greenish, the surface white appressed puberulent but largely concealed by the persistent, rigid, imbricate stipules; nodes 1-6, commonly 1.5 mm. apart; stipules 2.5-4 mm. long, broadly oblique ovate, the base cordate, the midrib heavy, raised, it and the central strip densely white appressed puberulent, the wide sides membranous, brown, glabrous, the margins white ciliate; petioles 3- 11 mm. long, white puberulent; blades 2.6 cm. long, 6-19 mm. wide, coriaceous, lanceolate, the margin perceptibly remotely low crenulate, above dark green, sublucid, white puberulent on the midrib and remotely so on the smaller veins, below yellowish green and similarly puberulent, strongly reticulate veined; the secondary veins 5-7 on a side, sharply ascending and inarched connecting well in from the margin;" (Bibref: 1786).
Flower: "Flowers solitary in axillary short shoots; corolla caducous, blue, weakly zygomorphic, petals prolonged into a "tube" with bottom petal slightly longer than others and weakly differentiated, scarcely saccate at base; filaments free, anthers dehiscing laterally". (Bibref: 1788). Sepals five, distinct, unequal, persistent. (Reslit: 2850). Flowers about 1.3 cm long and yellowish-green to whitish. (Bibref: 1786). Flowers whitish. Fragrant. Petals five. (Reslit: 2850).
Fruit: Fruit is a capsule, elliptical in shape, about 1 cm long and 0.6 cm wide. (Bibref: 1786). Thick-walled. (Bibref: 1788). "Petals and stamens marcescent, persisting around the fruit." (Bibref: 1788).

Bloom Information

Bloom Color: White , Green
Bloom Notes: Corollas pale green or greenish-white.


Native Distribution: Endemic to the Hawaiian islands. Native range limited to an area with a radius of about 2.4 km in the northwestern part of the Island of Hawaii." (Webref: 28).
Native Habitat: Dry scrub on old montane cinder cones. "Associated with Dodonaea, Wikstroemia, Railliardia Menziesii, Bidens filiformis, Sida, and Eragrostis. (Reslit: 2850).


Use Ornamental: Owing to the rarity of this species and its imperilied status, no horticultural use is warranted.
Warning: A critically imperiled endangered species. Specimens must not be collected or molested in any way.
Conspicuous Flowers: yes
Fragrant Flowers: yes

U.S. Fish & Wildlife Service Threatened & Endangered Status

USFWS Species Profile: Q2BU
Status: Endangered
Historic Range: U.S.A. (HI)
Critical Habitat: 17.96(a)
Special Rules: N/A
This information is derived from the U.S. Fish & Wildlife Serrvice Environmental Conservation Online System.

Web Reference

Webref 6 - Germplasm Resources Information Network - (GRIN) [Online Database] (2018) USDA, ARS, National Genetic Resources Program, National Germplasm Resources Laboratory, Beltsville, Maryland.
Webref 28 - NatureServe Explorer: An online encyclopedia of life (2018) NatureServe
Webref 27 - USDA Plants Database (2018) USDA, NRCS.

Additional resources

USDA: Find Isodendrion hosakae in USDA Plants
FNA: Find Isodendrion hosakae in the Flora of North America (if available)
Google: Search Google for Isodendrion hosakae


Record Modified: 2021-01-01
Research By: JAM

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