Green Amaranth

Amaranthus viridis L.

Synonyms - Amaranthus gracilis

Family: Amaranthaceae.

Names:

Amaranthus is from the Greek meaning "not to wither" and refers to the persistent flower spike.
Green Amaranth.

Summary:

Erect, or ascending almost hairless, annual herb. 300-1000 mm tall. Usually has distinct male and female flowers on the same plant. The greenish flowers are clustered on a branched inflorescence arising from the leaf axils or at the ends of branches.

Description:

Cotyledons:

Two.

Leaves:

Alternate. Pale green. Soft.
Stipules -
Petiole - 10-50 mm long.
Blade - Egg shaped to oblong. Prominent white veins on the underside. 20-80 x 8-60 mm. Hairless. Rounded or notched tip. Relatively soft.

Stems:

Erect, spreading or upward bending. Branched. Often striped with purple. Branches often have a red tinge. Up to 1000 mm long.

Flower head:

Dense, slender, soft, green or brown spikes in a loose branched form at ends of branches or in leaf axils. Axillary spikes up to 130 mm long and sometimes interrupted near the base. Terminal spike usually 40-70 mm long and 5 mm diameter and often with a red tinge. May be discontinuous near the base and spread into a loose panicle near the top.

Flowers:

Greenish. Separate male and female flowers on the same plant. Female flowers more numerous than the male flowers.
Bracts - Small, egg shaped about 1 mm long, with a short fine tip.
Ovary -
Perianth - Green, 3 segments with an acute tip but not sharply pointed. Free. Papery. Spreading. Oblong to egg or spoon shaped. 1.5-2 mm long (twice as long as the bract).
Stamens - 3-5. No staminodes.
Anthers - 2 celled.

Fruit:

Small, bladdery bag. 1.5-2 mm long. Almost globular. Wrinkly when on the plant. Only just longer than the perianth. Does not open to release seeds.

Seeds:

Single. Lens shaped or circular and flattened, shiny, red-brown. 1-1.5 mm across.

Roots:

Taproot

Key Characters:

Biology:

Life cycle:

Annual. Flowers November to March in southern areas and April to June in northern areas.

Physiology:

Reproduction:

Flowering times:

December to March mainly. (November to February around Perth and April to June in Northern WA.)

Seed Biology and Germination:

Vegetative Propagules:

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Origin and History:

Probably tropical America.
Widespread throughout the warmer regions of the world.

Distribution:

ACT, NSW, NT, QLD, SA, VIC, WA.

Courtesy Australia's Virtual Herbarium.

Habitats:

Disturbed areas. Cultivated areas.

Climate:

Soil:

Plant Associations:

Significance:

Beneficial:

Food - edible when cooked. Fodder plant but toxicity unclear. Grazed sparingly by stock.

Detrimental:

Weed of summer crops, vegetables, cultivated land, disturbed areas and gardens.

Toxicity:

Suspected to be toxic to poultry and stock.
High nitrate levels have been recorded

Symptoms:

Birds sit on ground and hang their heads for 3-4 hours before dieing. Dark coloured flesh.

Treatment:

Exclude poultry from infestations.

Legislation:

None.

Management and Control:

Thresholds:

Eradication strategies:

Herbicide resistance:

Biological Control:

Related plants:

Boggabri weed (Amaranthus mitchellii)
Dwarf Amaranth (Amaranthus macrocarpus)
Foxtail (Amaranthus paniculatus)
Love Lies Bleeding (Amaranthus caudatus)
Native Amaranth (Amaranthus interruptus)
Needleburr (Amaranthus spinosus)
Powell's Amaranth (Amaranthus powellii)
Redroot Amaranth (Amaranthus retroflexus)
Redshank (Amaranthus cruentus)
Rough fruited Amaranth (Amaranthus muricatus)
Slim Amaranth (Amaranthus hybridus)
Spreading Amaranth (Amaranthus deflexus)
South American Amaranth (Amaranthus quitensis)
Tumble-weed (Amaranthus albus)
Amaranthus graecizans.

Plants of similar appearance:

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P72. Photo.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). p331. Diagram.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P284. Photo.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P71.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #68.16.

Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). p94.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.