Quick Facts

Quick facts

  • Smooth-stem Turnip (Brassica barrelieri subsp. oxyrrhina) is only known to be naturalised in south-west Western Australia.
  • It is commonly associated with disturbed coastal sites, especially roadside verges.
  • Smooth-stem Turnip is very similar in appearance to many other Brassica weeds that occur in Australia, hence correct identification is crucial in its successful management.
  • Smooth-stem Turnip is considered to be a potentially significant weed of canola crops.

What Does It Look Like?

What is it?

Smooth-stem Turnip (Brassica barrelieri subsp. oxyrrhina) is an annual, occasionally perennial herb that grows to about 50 cm tall (occasionally up to 1 m tall). The stems are hairless and arise from a basal rosette of leaves. The basal leaves are 70–250 mm long and 16-65 mm wide and are deeply and jaggedly divided, with the tips of the lobes pointing backwards to the base of the leaves. The stem leaves are small, less than 10 mm long, un-lobed, hairless, and are either present in small numbers or are absent.

The flowers occur in long racemes (unbranched flowering branches) up to 50 cm long and consist of four, white to pale yellow petals with purple venation. Each petal is up to 8 mm long.

The fruits are long and narrow, 25–60 mm long and 1.5–2.5 mm wide, with a short slender tip and slight constrictions between each of the seeds along the length of the fruits. Each fruit contains up to 17 seeds. The seeds are small, 1–1.5 mm diameter, and are brown to black in colour when ripe (Hewson 1982; Marchant et al. 1987).

For further information and assistance with identification of Smooth-stem Turnip, contact the herbarium in your state or territory.

Flower colour

  • Yellow
  • White

Growth form (weed type/habit)


Where it currently grows? Preferred habitat

Smooth-stem Turnip has been recorded growing on disturbed coastal sites and road verges in south-west Western Australia (Hussey et al. 2007). It is recorded as growing on sandy soils on roadsides, creek banks, woodland and scrubland (Western Australian Herbarium 2007). Where native, it occurs primarily on sandy soils (Ball 1996).

Are there similar species?

In Australia, there are numerous weedy cruciferous species that are similar in appearance to Smooth-stem Turnip. This species is distinguished by a combination of the stem leaves being much reduced or absent, or when present the leaves are stem clasping (Hewson 1982).

Why Is It A Weed?

What are its impacts?

Agriculture: Smooth-stem Turnip has the potential to become a significant weed of canola crops (Salisbury 2002).

Native ecosystems: Smooth-stem Turnip has been recorded invading disturbed and intact bushland in Western Australia (Western Australian Herbarium 2007) as well as disturbed coastal sites and road verges in Perth (Western Weeds n.d.).

How does it spread?

Although no published information is available on the dispersal mechanisms used by Smooth-stem Turnip, it is assumed that it spreads in the same manner as other similar weedy cruciferous species such as Wild Radish (Raphanus raphanistrum) and Sand Rocket (Diplotaxis tenuifolia). These species spread by water, especially where plants grow in riparian habitats and on steep terrain where erosion and runoff occurs. Contaminated soil, fodder, vehicles and other equipment are potential vectors for seed transport. Seeds may also be readily dispersed along roadsides during roadside maintenance works. Dispersal via contaminated agricultural produce is also a potential means of spread (Parsons & Cuthbertson 2001).

What is its history in Australia?

Smooth-stem Turnip was first recorded in Australia from Brunswick Junction, Western Australia in 1966 (Western Australian Herbarium 2007). It is unknown how or why the species was introduced into Australia.

How To Manage It?

Best practice management

No information regarding the control of Smooth-stem Turnip is available. It can be assumed that similar control methods to those used on other Brassica weed species could be employed on Smooth-stem Turnip.

Does it have a biological control agent?


When does it grow? (lifecycle/growth calendar)

Smooth-stem Turnip is an annual or occasionally perennial species. In Western Australia, it flowers during September and October (Marchant et al. 1987).

Where Is It Found?

Which states and territories is it found?


What areas within states and territories is it found?

In Australia, Smooth-stem Turnip is only known to be naturalised in Western Australia, where it occurs on disturbed sites on the Coastal Plain (Marchant et al. 1987). It has also been recorded occasionally from the wheat belt, and road verges north of Perth (Hussey et al. 2007).

Where does it originate?

Smooth-stem Turnip is native to northern Africa (Morocco) and south-western Europe (Portugal and Spain) (GRIN 2007).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?


Where is it a declared weed?


Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?


Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?


Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Brassica barrelieri subsp. oxyrrhina

Other scientific names (synonyms)?

Sinapis oxyrrhina Coss.

Does it have other known common name(s)?

Smooth-stemmed Turnip

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