Amaranthus viridis is one of two non-native Amaranthus species traditionally found on Kure. A. spinosus is either gone or is very rare. A. viridis is one of the few broad leafed non-native shrubs that does not have dentate (toothed) margins (leaf edges). The leaves are somewhat triangulate to diamond shaped (technically deltate-ovate to narrowly rhombic) and have a distinct central nerve. Amaranthus viridis is found in camp but is rare.
Amaranthus cotyledons most closely resemble those of Chenopodium (below left). Both are linear to lanceolate (lance shaped), widest about 1/3rd of the distance from the base to the tip, and rounded at the tip. The true leaves are distinctive at a young age, Chenopodium with dentate (toothed) margins, Amaranthus (below right) with entire (not dentate) margins. Amaranthus is found only infrequently but this may be because it is overlooked. The two common sites for it are near the sea grape tree south of the main building, and in the area to the east of the trail from the main building to the cistern and south of the cistern.
Description: Monoecious annual herb stems erect or occasionally ascending, 1-8 (-10) dm long, sparingly to densely branched, striate, glabrous and usually becoming pubescent with multicellular hairs above. Leaves deltate-ovate to narrowly rhombic, blades 2-7 cm long, 1.5-5.5 cm wide, Amaranthus viridis (PIER species info) http://www.hear.org/pier/species/amaranthus_viridis.htm. Glabrous or lower surface pilose along the veins, apex usually narrow and with a small narrow emargination, petioles 1-10 cm long. Flowers green, in slender, axillary or terminal and often paniculate spikes, sometimes in axillary clusters in lower part of plant, both sexes mixed throughout the spikes, but pistillate flowers more numerous, bracts and bracteoles whitish, deltate-ovate to broadly lanceolate, membranous, with a short, pale or reddish awn; sepals 3 (4), those of staminate flowers ovate-oblong, ca. 1.5 mm long, apex acute, mucronate, those of pistillate flowers narrowly spatulate to oblong, 1.3-1.8 mm long, apex more or less mucronate; stigmas 2-3. Fruit subglobose, 1.3-1.5 mm long, not or only slightly exceeding the sepals, indehiscent or rupturing irregularly at maturity, conspicuously rugose throughout. Seeds dark brown to black, more or less shiny, slightly compressed, 1-1.3 mm long, reticulate and with shallow outgrowths on the reticulum (Wagner et al., 1999; p. 189).