green amaranth

Amaranthus viridis
upright habit growing in a garden (Photo: Sheldon Navie)
spreading habit growing in a lawn (Photo: Sheldon Navie)
leaves and flower clusters (Photo: Sheldon Navie)
close-up of leaves (Photo: Sheldon Navie)
branched, reddish-coloured, flower cluster (Photo: Sheldon Navie)
close-up of immature fruit (Photo: Sheldon Navie)
close-up of mature fruit (Photo: Sheldon Navie)
seedlings (Photo: Sheldon Navie)
young plant (Photo: Sheldon Navie)

A short-lived herbaceous plant growing to 1 m tall. Its leaves are light green and often have notched tips. Its tiny greenish or reddish flowers are borne in dense elongated clusters at the tips of the branches.

Common names 
Also known as: green amaranth, green pigweed, slender amaranth, Prince of Wales feather,
Flowering time 
Year round
Native to tropical America.
Council declaration 
SIL – Special Investigation List
Known distribution 

Widely naturalised along the north and east coast of Australia. Including northern territory, coastal Qld and northern NSW.


This species is a very common garden weed. It is also a weed of disturbed sites, waste areas, footpaths, roadsides, parks, pastures, crops and cultivation, and riparian vegetation.


A short-lived (i.e. annual) herbaceous plant with an upright (i.e. erect) or spreading (i.e. decumbent) habit. It usually grows 40-100 cm tall, but occasionally reaches up to 1.5 m in height.

Impact and control methods 
Stem and leaves 

The stems can be hairless (i.e. glabrous) or sparsely hairy (i.e. puberulent). The hairless (i.e. glabrous) leaves are alternately arranged along the stems and borne on stalks (i.e. petioles) 7-70 mm long. These leaves (1.5-15 cm long and 1-5.5 cm wide) are egg-shaped in outline (i.e. ovate) to almost triangular in shape. They have entire margins and blunt, pointed or notched tips (i.e. obtuse, acute or emarginate apices).

Flowers and fruits 

The tiny flowers have three 'petals' (i.e. tepals or perianth segments) 1.5-2 mm long. They are borne in branched clusters (5-10 cm long) at the tips of the stems (i.e. in terminal panicles) and also in smaller clusters in the forks of the upper leaves (i.e. in axillary clusters). These flower clusters (i.e. inflorescences) can be greenish, pinkish or reddish-brown in colour. Flowering occurs throughout the year. The tiny fruit (i.e. utricles) are 1.5-2 mm long and have a wrinkled surface. Each of these fruit contain a single blackish-brown seed (1-1.5 mm across) with a warty surface texture.