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Amaranthus polygonoides

L. (1759)

This name is accepted

Kingdom: Viridiplantae Phylum: Magnoliophyta Class/Clade: Eudicot-CoreEudicot Order: Caryophyllales Family: Amaranthaceae Genus: Amaranthus

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Description

Key Characters:

Growth Form: Plants annual.

Stems: Stems glabrescent proximally, pubescent distally, becoming glabrous at maturity. Stems erect-ascending to prostrate, branched mostly at base and in proximal 1/2, 0.1–0.5 m.

Roots:

Leaves: Leaves simple. Alternate. Blades ovate, obovate-rhombic to narrowly ovate, sometimes lanceolate, 1.5–3(–4) × 0.5–1.5(–2) cm. Apex rounded, obtuse, or emarginate, mucronate. Base cuneate. Margins entire to undulate-erose. Petioles ± equaling blade. Stipules absent.

Flowers: Inflorescences axillary, congested clusters. Bracts of pistillate flowers lanceolate or linear, 1–1.5 mm, 1/2 as long as tepals. Plants monoecious: Pistillate flowers: tepals 5, connate in proximal 1/3 (entirely distinct in all other species), with 3 prominent veins abaxially, spatulate or somewhat clawed, equal or subequal, 2–3 mm, apex rounded or retuse, mucronate; style branches somewhat spreading; stigmas 3. Staminate flowers intermixed with pistillate; tepals (4–)5; stamens 2–3.

Fruit: Utricles cylindric or narrowly turbinate; 2–2.5 mm; ± equaling tepals; smooth proximally or roughened toward tips; indehiscent or tardily dehiscent. Seeds dark reddish brown to black; lenticular; 0.8–1 mm diam.; shiny.

Ploidy:

Habitat:

Elevation Range:

Historical Distribution

Images

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Uses and Culture

USES

Natural History

Statewide Status

Naturalized

Island Status

Kaua'i Naturalized
O'ahu Naturalized
Maui Naturalized

Dispersal Agents


Pollinators

Bibliography

Name Published In: Pl. Jamaic. Pug.: 27 (1759)

Other References

Frohlich & Lau 2020:56 (NEWNAT/O, DESCR); Ross & Faccenda 2023a:39 (O, RANGE EXT [now widespread in leeward areas]); Faccenda & Ross 2024:28, 30 (K, KEY); Faccenda, Arthur, et al. 2025:152 (EM)

Occurrences

SNo. Scientific Name Locality Habitat Basis of Record Description Recorded By Record Number Island Source Date
1 Amaranthus polygonoides Kihei, South Maui Community Park on Liloa Dr Weedy, sunny area on edge of parking lot Preserved_Specimen Leaves with white chevron Starmer, J. Maui BISH 2024-06-09
2 Amaranthus polygonoides Port Allen, Aka Ula St, industrial area near petroleum station and solar park Roadside, dry, sunny area near parking lot Preserved_Specimen Leaves bluish green and with white chevron centered on the leaf. One plant seen, rare Faccenda, K. 2477 Kauai BISH 2022-06-03
3 Amaranthus polygonoides Hawai'i Kai, Kamilo'iki park off of Lunalilo Home Rd In water retention basin at NW corner of park Preserved_Specimen Common only in this depression, approximately 50 plants seen in mowed area Faccenda, K. 2857 Oahu BISH 2022-12-03
4 Amaranthus polygonoides Ka Iwi Shoreline Trail. Near Kalanianaole Hwy across from the Hawaii Kai Golf Course Disturbed coastal shrubland and grassland. Growing along a roadside trail area with Leucaena, Megathyrsus, Malvastrum, Sida, Elesine, and Euphorbia. Sparsely naturalized along the Ka Iwi Shoreline trail Preserved_Specimen Ascending annual herb, branching from base, ca. 10-20 cm. height; inflorescences axillary; stamens 2; tepals 5; pistillate tepals connate at base. Ross, M.C. 1810 Oahu BISH 2021-03-28
5 Amaranthus polygonoides UH Manoa Campus. Varney Circle Crack in asphalt between road and curb Preserved_Specimen One individual in area Faccenda, K. 1702 Oahu BISH 2021-01-06
6 Amaranthus polygonoides Ka Iwi Shoreline Trail. Near Kalanianaole Highway across from the Hawaii Kai Golf Course Disturbed coastal shrubland and grassland. Growing along a roadside trail area with Leucaena, Megathyrsus, Malvastrum, Sida, Eleusine, and Euphorbia. Sparsely naturalized; ca. 20-30 plants Preserved_Specimen Ascending annual herb, branching from base, ca. 10-20 cm. in height; inflorescences axillary; stamens 2; tepals 5; pistillate tepais connate at base. Ross, M.C. 1807 Oahu BISH 2021-02-09
7 Amaranthus polygonoides Waianae HDOT baseyard Growing in ruderal roadside vegetation; low-growing herb in a mowed field. Seen occasionally on property, not common. Preserved_Specimen Lau, A. 2019092101 Oahu BISH 2019-09-21
8 Amaranthus polygonoides Waikele, HI Westbound off ramp Dry to mesic disturbed roadside; herbs about .33 meters tall, upright, one single stem with branching near base. About 100 plants in a small patch. Preserved_Specimen Lau, A. 2018121201 Oahu BISH 2018-12-12
9 Amaranthus polygonoides Kihei, South Maui Community Park on Liloa Dr Weedy, sunny area on edge of parking lot Preserved_Specimen Leaves with white chevron Starmer, J. Maui BISH 2024-06-09
10 Amaranthus polygonoides Ka Iwi Shoreline Trail. Near Kalanianaole Highway across from the Hawaii Kai Golf Course Disturbed coastal shrubland and grassland. Growing along a roadside trail area with Leucaena, Megathyrsus, Malvastrum, Sida, Eleusine, and Euphorbia. Sparsely naturalized; ca. 20-30 plants Preserved_Specimen Ascending annual herb, branching from base, ca. 10-20 cm. in height; inflorescences axillary; stamens 2; tepals 5; pistillate tepals connate at base. Ross, M.C. 1809 Oahu BISH 2021-03-23
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