Weed Alert: Kochia

Kochia (Kochia scoparia)

The Problem | Identification | Propagation | Control | Legislation

Also known as Bassia scoparia
Other common names are burning bush, summer cypress, mock cypress.

World Status

Kochia is native to eastern Europe and western Asia. It has become naturalised throughout Europe and parts of temperate Asia. It is recorded as a weed in Argentina, Canada and the United States.

It was initially grown as an ornamental hedge around gardens, or used as a backdrop planting because of its dense conical shape and attractive colour in autumn. It has since escaped cultivation and today it is one of the most widespread and troublesome weeds of US agriculture.

It was introduced to Western Australia in 1990 as a fodder plant for salt-affected land, but has since escaped cultivation and is now subject to an eradication program.

Kochia appeared in Tasmania as a contaminant of carrot seed in 1995, 1997 and 1998. All infestations have been eradicated and previously infested areas are checked annually.

The Problem

Kochia is able to grow in a wide range of soil types, is drought tolerant, resistant to insect attack, toxic to livestock and able to rapidly spread long distances. It produces allelopathic compounds that inhibit the growth of nearby plants.

It has the potential in Australia to infest pastures, crops, roadsides, railway lines and amenity areas. Once the plant gets into paddocks, it will significantly reduce pasture and crop production.

Dead plants break off at ground level and are blown large distances by the wind. This ‘tumbleweed’ mechanism is capable of spreading seeds up to a kilometre from the original plant site.

Identification

• Habit - Kochia is an erect annual, growing 20–150 cm tall. It usually has a main stem that bears many upwardly-curving branches, that give the plant a dense, compact appearance.
• Leaves - The leaves are flat and alternate, up to 50 mm long and 8 mm wide, with three longitudinal veins on the underside. Leaves are usually without petioles (leaf stems) and often have hairy margins. The young shoots are usually hairy.
• Flowers - Flowers are small and indistinct, located towards the tips of the branches.
• Colour - As the plant ages, its colour often changes from green to pale yellow, pink and then ‘rusty’ brown.
• Fruit - The fruit is small (2 mm across), star shaped and contains a single seed.

Propagation

Kochia reproduces by seed only. The species typically produces around 14,600 seeds per plant in late summer. Seeds are dispersed in autumn when the plant becomes a ‘tumbleweed’. Seeds mostly germinate in spring or as suitable conditions allow.

Seeds appear to have a relatively short life in the soil.

Control

There is no registered herbicide in NSW for the control of kochia.

Early tillage in spring gives good control of the kochia seedlings. Mowing or slashing the plants before flowering is effective in reducing seed production but will not kill the plant.Seedlings are susceptible to strong plant competition.

There are currently no known biological control agents.

Legislation

The importation of kochia into Australia is prohibited under Australian quarantine regulations.

Kochia scoparia is a Class 1 noxious weed throughout NSW under the NSW Noxious Weeds Act 1993. This weed must be eradicated from the land and the land must be kept free of the plant. As a notifiable weed, all outbreaks must be reported to the local council.

Summer or mock cypress (Kochia scoparia subsp. Tricophylla) is exempt from declaration.

Acknowledgements

Jeff Burton Extension Officer (Weeds) NSW Agriculture

Sources of information

• Department of Agriculture Western Australia web site. www.agric.wa.gov.au
• Department of Primary Industries Water and the Environment web site, Tasmania. www.dpiwe.tas.gov.au
• Washington State Noxious Weed Control Board web site. www.wa.gov/agr/weedboard