Flora of the Hawaiian Islands
Dicotyledon Literature for Justicia betonica
Wagner et al., 1990, 1999.
   Acanthaceae -- The Acanthus Family Bibliography
      Justicia betonica

Common name(s): water willow, squirrel's tail, white shrimp plant
General Information
DistributionNative to tropical Asia, often cultivated.In the Hawaiian Islands, naturalized on Kaua`i, O`ahu, Moloka`i, Lana`i, Maui, Hawai`i. First collected Hawai'i in 1943 [Fagerlund & Mitchell 475, BISH].
















HabitatIn Hawai'i often escaping cultivation and forming large stands on Kaua'i, O'ahu, Moloka'i, Lana'i, Maui, and Hawai'I
Habit
Coarse perennial herbs 0.5-2.5 m tall; stems tinged purple, glabrous to puberulent in lines on the upper stem.
Leaves
Leaves green, lower surface slightly paler, broadly ovate to elliptic, 9-22 cm long, 3.5-12 cm wide, sparsely strigillose along the margins and veins, petioles 0.5-4 cm long.
Flowers
Flowers in axillary and terminal spikes, each one subtended by 3 white bracts with conspicuous green veins, the large outer bract ovate, ca. 15 mm long, 10 mm wide, the inner 2 about as long, ca. 5 mm wide; calyx green, 5-lobed, the lobes narrowly lanceolate, ca. 5 mm long; corolla pale lavender with a white spot outlined with purple on the lower lip, tubular, 14-17 mm long, distinctly 2-lipped.
Fruit
Capsules clavate, somewhat compressed parallel to the line of dehiscence, 2-lobed by protrusion of the seeds, 1.3-2 cm long, puberulent.
Seeds
Seeds ca. 2.5-3 mm in diameter, suborbicular, compressed, pale brown, surface papillose-arcuate.
Chromosomes
2n = 28, 34.
Notes
In Hawai'i often escaping cultivation and forming large stands on Kaua'i, O'ahu, Moloka'i, Lana'i, Maui, and Hawai'i. This plant is potentially a serious weed (Neal, 1965; Degener & Degener, 1962)