Quick Facts

Quick facts

  • Penny Cress (Thlaspi arvense) is a widespread and significant weed of crops throughout the temperate regions of the world.
  • In Australia, Penny Cress is an uncommon weed that has only been recorded on a handful of occasions.
  • Penny Cress is a declared weed in Western Australia.
  • Leaves and seeds of Penny Cress can be toxic to livestock.

What Does It Look Like?

What is it?

Penny Cress (Thlaspi arvense) is a hairless, erect, annual herb (occasionally biennial) that grows up to 60 cm tall. The lower leaves (up to 5 cm long) are oblong to lance-shaped and are slightly toothed. The upper leaves are similar in appearance to the lower leaves, but diminish in size along the stems and clasp the stem at the base of the leaf.

The flowers consist of four, very small, white petals (up to 4 mm long).

The fruits are more or less circular in outline (12-22 mm diameter), strongly flattened and have two, broad, thin wings. A deep notch is present at the end of the fruit. Each fruit contains several small seeds (1.5-2 mm long) that are purplish-brown in colour when ripe. Penny Cress has an unpleasant odour that is especially noticeable when the plant is crushed (Hewson 1982; Retter & Harden 1990).

For further information and assistance with identification of Penny Cress contact the herbarium in your state or territory.

Flower colour


Growth form (weed type/habit)


Where it currently grows? Preferred habitat

Penny Cress is a weed of wet places (Richardson et al. 2006) and is adapted to a wide range of environmental conditions in temperate climates (Warwick et al. 2002).

Are there similar species?

Several species of Lepidium (native and exotic) that occur in Australia may be mistaken for Penny Cress. The fruits of Penny Cress are much larger (up to 22 mm wide) than those of other Lepidium species (up to 9 mm wide). In addition, the fruits of Penny Cress contain several seeds, whereas the fruits of Lepidium species contain only two seeds.

Several other white-flowered members of the Brassicaceae family may be confused with Penny Cress. For example, Shepherd's Purse (Capsella bursa-pastoris) is an annual species that is almost hairless, its fruits are triangular or almost heart-shaped in outline. Hoary Cress (Lepidium draba) [as Cardaria draba] is a common perrenial weed that is densly covered in fine soft hairs, its fruits are shaped like upside down pears and are inflated (Navie 2004).

Why Is It A Weed?

What are its impacts?

Penny Cress is a serious weed of crops, gardens, pastures, disturbed sites and waste areas in temperate and sub-tropical regions of the world (Navie 2004; Warwick et al. 2002).

Agriculture: It is an annual pioneer of disturbed soils and in North America, it is known to be an important weed of grain, oilseed and forage crops. When present in hay or other fodder, its seeds and leaves can be toxic to animals, as well as tainting milk and meat with unpleasant flavours (Warwick et al. 2002). Poisoning, death and abortion have occurred in cattle in western Canada that have ingested hay containing high quantities of Penny Cress (Smith & Crowe 1987).

How does it spread?

Penny Cress is an annual species, hence reproduction occurs by seed production. Canadian studies have shown that Penny Cress can produce up to 15 000 seeds per plant. Seed dormancy is enhanced by the thick seed coast and seeds can remain viable for up to 20 years. (Warwick et al. 2002). Seeds of Penny Cress are most often spread as a contaminant of agricultural produce (Navie 2004).

What is its history in Australia?

Penny Cress was possibly introduced into Australia as a contaminant of imported crop seeds (Baker 2007).

In New South Wales, Penny Cress has been recorded twice in the Northern Tablelands (from Guyra in 1934 and Glen Innes in 1939). In Tasmania, it has been recorded only once as a weed in a canola crop (Brassica x napus) in 1991, from Pawtella (Baker 2007). In Victoria, it has been reported infrequently, with only one specimen held at the Melbourne Herbarium, taken from a pea crop at Leongatha South in 1942 (National Herbarium of Victoria 2007). The species is now believed to be absent from Victoria (Ross & Walsh 2003).

How To Manage It?

Best practice management

Chemical control: Effective control of Penny Cress can be achieved using herbicides (Warwick et al. 2002). However, plants resistant to Group B/2 herbicides have been found in Canada (Beckie 1993; Warwick et al. 2002; Beckie et al. 2007).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au 

Does it have a biological control agent?


When does it grow? (lifecycle/growth calendar)

Penny Cress is generally a summer annual, but can also germinate in winter crops. Flowering occurs mostly during late spring, summer and early autumn in Australia (Navie 2004). In New Zealand, plants have been recorded flowering throughout the year (Garnock-Jones 1988).

Where Is It Found?

Which states and territories is it found?


What areas within states and territories is it found?

Penny Cress is a weed of waste places on the Northern Slopes and Tablelands of New South Wales. It has also been recorded from Pawtella in Tasmania and Leongatha South, Victoria, although it is now believed to be absent from this state. It is also found in south-east Queensland (Hewson 1982; Retter & Harden 1990; Navie 2004).

Where does it originate?

Penny Cress is considered native in temperate and tropical Asia, Macaronesia, and throughout Europe (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

Thlaspi arvense

Other scientific names (synonyms)?


Does it have other known common name(s)?

Frenchweed, French Weed, Fanweed, Fan Weed, Field Pennycress, Field Penny Cress, Field Penny-cress, Pennycress, Stinkweed, Stink Weed, Common Pennycress, Bastard Cress, Bastardweed, Devil Weed, Mithridate Mustard, Dish Mustard, Wild Garlic

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