Redshank (Amaranth)

Amaranthus cruentus, Amaranthus retroflexus

Redshank, like other amaranths, grow quickly, are prolific seeders and can tolerate a range of growing conditions. In mainland Australia, Amaranthus cruentus is found in southern states, most commonly as a horticultural weed. In Tasmania, redroot amaranth (Amaranthus retroflexus) is also referred to as redshank.

Refer to the link below for more detailed information on specific amaranth species. Note: Persicaria maculosa is also referred to as Redshank, but is not dealt with here.

Description

Redshank is an erect, annual herb with branched stems to 1.5 m tall. The leaves of redshank are alternate, commonly dark green with a red tinge and slightly wavy on the edges. The flower spike is also erect, fairly dense and commonly red in colour, and may be up to 300 mm long. Redshank fruit is thin walled and contains a number of seeds.

Redshank can be confused with sIim amaranth (Amaranthus hybridus) however the flower head of slim amaranth is spikier in appearance.

Control

Both Tramat® and Betanal® Flow are registered for the control redshank in beet crops. Roundup Ultra® MAX, Roundup Ready® with Plantshield® and Roundup Ready PL are registered for the control of amaranth species in certain situations.

Related Pests

Amaranths

Amaranthus spp.

Amaranths are a group of broadleaf weeds that are particularly problematic in broadleaf vegetable crops and summer crops such as cotton. Species include green amaranth (Amaranthus viridis), dwarf amaranth (A. macrocarpus), Boggabri weed (A. mitchelli) and redshank (A. cruentus). Tumbleweed (A. albus) is a more temperate weed, found in crops and roadsides in NSW, Vic, SA and WA. In addition to having key weed attributes of rapid growth rates, being prolific seeders, high genetic diversity, and the ability to tolerate a range of growing conditions, some amaranth species, such as Palmer amaranth, have developed resistance to glyphosate in the USA.

Refer to the link below for more detailed information on specific amaranth species.

Dwarf amaranth - Boggabri weed

Amaranthus macrocarpus var. pallidus and var. macrocarpus

Dwarf amaranth is an annual herb that is most commonly a weed of irrigated summer crops and fallows in eastern Australia. Dwarf amaranths can also be a pathogen host for some cotton diseases. It is more commonly associated with, but not restricted to, clay soils. Dwarf amaranths like other amaranths, grow quickly, are prolific seeders and can tolerate a range of growing conditions.

Refer to the link below for more detailed information on specific amaranth species.

Green amaranth

Amaranthus viridis

Green amaranth is widely naturalised in many parts of Australia but is more commonly associated with the coastal fringes. In addition to being a cropping weed, it is also a very common garden weed. Green amaranth, like other amaranths, grows quickly, is a prolific seeder and can tolerate a range of growing conditions.

Refer to the link below for more detailed information on other amaranth species.

References

Agrobase Australia (Viewed April 2020), ‘Redshank (Amaranthus)’, https://agrobaseapp.com/australia/weed/redshank-amaranthus

Herbiguide (2014), ‘Redshank (Amaranthus)’, Herbiguide, http://www.herbiguide.com.au/Descriptions/hg_Redshank_Amaranthus.htm