Dwarf Amaranth

Amaranthus macrocarpus Benth.

Family: Amaranthaceae.

Names:

Dwarf Amaranth refers to the small size of this plant compared to other Amaranth species. Amaranthus is from the Greek meaning "not to wither" referring to the persistent flower spike. Macrocarpus means large fruit and refers to the fact that the fruit of this species is almost twice as large as other Amaranth species.

Other Names:

Boggabri weed is also used for this plant and A. mitchellii.

Summary:

An small, hairless, scentless, prostrate or semi erect, annual herb with short rounded leaves on long stems. Up to 300 mm tall.

Description:

Cotyledons:

Two.

First leaves:

Leaves:

Alternate.
Stipules -
Petiole - As long as the leaves.
Blade - Lateral veins easy to see underneath. Egg shaped to oblong with pointed tip or rounded. 10-20 mm long. Tapering into a long stalk. Hairless.

Stems:

Up to 300 mm tall. Weak, branched. Hairless.

Flower head:

Globular cluster in leaf axils.

Flowers:

Greenish. Separate male and female flowers on the same spike.
Bracts - 2 bracts shorter than the perianth. Greenish.
Ovary - -3 prominent styles.
Perianth -3-5 segments. 5 mm long and longer than the bracts. Lance shaped with dry membranous edges. Pointed tip.
Stamens - 3-5.
Anthers -

Fruit:

Dark brown to almost black when ripe. Membranous. Oblong. 3-5 mm long. Much longer than the perianth. Wrinkled. Persistent. Bottle-shaped with 2-3 obvious styles.

Seeds:

Single. Dark brown to black. Shiny. Larger any than other Australian Amaranthus species.

Roots:

Taproot.

Key Characters:

Biology:

Life cycle:

Annual. Flowers in summer.

Physiology:

Reproduction:

Flowering times:

Summer.

Seed Biology and Germination:

Vegetative Propagules:

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Origin and History:

Australia.

Distribution:

ACT, NSW, QLD, SA, VIC.

Courtesy Australia's Virtual Herbarium.

Habitats:

Depressions and low lying areas.

Climate:

Soil:

Often on clay soils.

Plant Associations:

Wide range.

Significance:

Beneficial:

Moderately palatable.

Detrimental:

A weed of irrigated summer crops and summer fallows.
A minor weed of pastures.

Toxicity:

May cause nitrate poisoning. It is rarely present in sufficient quantities to cause problems.

Symptoms:

Treatment:

Legislation:

None.

Management and Control:

Thresholds:

Eradication strategies:

Herbicide resistance:

Biological Control:

Related plants:

Boggabri weed (Amaranthus mitchellii)
Foxtail (Amaranthus paniculatus)
Green Amaranth (Amaranthus viridis) has no staminodes.
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)
Tumbleweed (Amaranthus albus) has tiny flowers in the leaf axils.
Amaranthus graecizans.
Batchelor's Buttons (Gomphrena spp.)
Cockscomb (Celosia spp.)

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). P70. Photo.

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

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). p282. Photo.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P69. Diagram.

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). #68.8.

Acknowledgments:

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