Quick Facts

Quick facts

• Originally from eastern Mediterranean and Asia, Hoary Cress (Lepidium draba) is a major weed of cropping across much of temperate Australia, causing serious impacts to crop yields.
• In Western Australia, Hoary Cress is currently an uncommon weed but could potentially cover large areas of south-western Western Australia.
• Cultivation techniques used in Australian cropping favours the regeneration and spread of Hoary Cress through the movement of root fragments that readily sprout.
• An integrated approach to weed management utilising different weed control techniques can significantly reduce the impact of Hoary Cress on Australian agricultural producers.

What Does It Look Like?

What is it?

Hoary Cress (Lepidium draba) is an erect, or flat to erect perennial herb that grows 150 mm up to 900 mm tall with few stem branching at the top. The numerous roots producing adventitious buds producing new plants. The stems and leaves are densely covered in soft, minute hairs, giving the plant a greyish green or bluish green colour. The alternate lower leaves are shortly stalked, obovate (egg-shaped with widest end at the tip) to elliptic (oval), long and narrow, up to 100 mm long, and have toothed or untoothed edges. The upper leaves are toothed or entire, but have no stalk and instead clasp the stem with margins broadly toothed.

The white flowers are crowded into many dense, flat-topped clusters with 100s and 100s of flowers produced. Each flower consists of four, small, white petals 3–4 mm long, surrounded by 4 green sepals about 2 mm long. Style single,1–2 mm long,

The fruits are cordate (shaped like an upside down heart), 3–5 mm long, 3.5–5 mm wide, on a stalk (pedicels) 4–15 mm long. Fruits are inflated, tips obtuse (blunt or rounded; converging edges making an angle of more than 90°), and fruits have two inflated chambers separated in the middle that each contains 1–2 seeds. The seeds are small (approximately 2 mm long), oval in shape and dark reddish-brown in colour when ripe (Scurfield 1962; Hewson 1982; Entwisle 1996; VicFlora 2016).

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

Flower colour

White

Growth form (weed type/habit)

Herb

Where it currently grows? Preferred habitat

Hoary Cress (Lepidium draba) grows on a wide range of soil types but prefers alkaline soils, particularly black and red clay loams. It thrives on the more friable, deep and rich soils that enable rapid lateral root growth (Lyons 1998; Faithfull 1998). Hoary Cress favours disturbed sites such as roadsides, waste places, drainage lines and irrigation ditches (Scurfield 1962; Lyons 1998).

Are there similar species?

Several other species of Lepidium (native and exotic) occur in Australia and may be mistaken for Hoary Cress. The fruit of Hoary Cress is more or less rounded or inflated, while those of other Lepidium species are generally strongly flattened. In addition, the fruits of Hoary Cress do not open at maturity, while the fruits of other Lepidium species open at maturity to release the seeds. Several other white-flowered members of the Brassicaceae family may also be confused with Hoary Cress, such as:

Shepherd's Purse (Capsella bursa-pastoris). It is an annual species that is almost hairless, its fruits are triangular or almost heart-shaped (cordate) in outline.

Penny Cress (Thlaspi arvense) is an uncommon annual weed which is hairless. Its fruits are relatively large (10-20 mm long) and are rounded in outline (Navie 2004).

Why Is It A Weed?

What are its impacts?

Hoary Cress (Lepidium draba) is a significant weed of crops, reducing yields through competition. It is widespread on arable land, waste ground and roadsides drainage lines and irrigation ditches and can spreads to nearby areas or further by water.

Agriculture: In Australia, it is a weed of grain crops, pastures and horticultural crops such as vegetables, orchards and vineyards, and causes serious yield reductions and may interfere with harvesting in cereal and other crops It is a weed of both cultivation and minimum tillage systems. In established lucerne it can be competitive if present in large numbers. It is seldom grazed but milk and meat may become tainted if plants are consumed for about a week after ingestion. It has poisonous properties and is suspected of causing stock losses but rarely eaten in sufficient quantity to cause problems. Established infestations are very difficult to eradicate, mainly because of the vigorous perennial root system. The roots of Hoary Cress contain chemicals that hinder the germination and growth of companion plants, especially cereals. Infestations can completely dominate fields and, when in flower, form massive drifts of white (Faithfull 1998; Agriculture Western Australia 2005; Parsons & Cuthbertson 2001; DPIW 2002). A highly competitive weed and may carry viruses and diseases of Brassica crops. As it is part of the Brassica family, it poses a major problem when canola or similar cops in the family are grown is part of the cropping rotation, as it cannot be controlled in-crop (DPI NSW 2019).

Native ecosystems: Not normally a weed of native areas, but found in disturbed riparian areas.

Urban areas: A weed of roadsides, creeks and drains and potentially parks and gardens.

How does it spread?

Hoary Cress can spread by the dispersal of both seed and root fragments, and through the growth of lateral roots

Hoary Cress has an extensive and persistent root system and most new plants arise from its spreading roots and broken root segments. The well developed lateral roots produce new shoots from buds that occur along its length. Cultivation is a common cause of root spread (DPI NSW 2019). Regeneration of plants from root fragments following cultivation is rapid and this is the primary means of spread for this weed species (Faithfull 1998; Parsons & Cuthbertson 2001; DPIW 2002). In a trial in Tasmania, root fragments of 2 cm long that were buried 10 cm deep readily emerged (DPIW 2002). Spread by contaminated soils on machinate and vehicles and earth works.

Thousands of seeds are produced per year by each plant, with around 80% viability. Seeds can be spread by contaminated soil, hay, grain, vehicles and equipment (DPI NSW 2019). It is a prolific producer of seed, with up to 850 fruits being produced per flowering stem (Lyons 1998).  Seed may be an insignificant method of reproduction in established infestations but can be a significant method of spread into new areas (DPIW 2002). Seeds of Hoary Cress spread in the same manner as other similar weedy cruciferous species such as Wild Radish (Raphanus raphanistrum) and Sand Rocket (Diplotaxis tenuifolia). The seed of these species spreads by water, especially where plants grow in riparian habitats and on steep terrain where erosion and runoff occurs.

General spread for seed are contaminated soil, fodder, vehicles and cultivation equipment and seeds and roots 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?

Hoary Cress was first recorded in Australia in 1882, from Hobart, Tasmania, and soon after from Victoria in 1883. It was later recorded at Dubbo, New South Wales in 1898. It had reached Merredin, Western Australia, and the Darling Downs, Queensland, by the early 1920s. Seeds of Hoary Cress were most likely introduced into Australia as a contaminant of imported crop or pasture seeds. It was not until the 1930s that the importance of this species as a crop weed was realised. It competed strongly with wheat crops, could not be controlled easily, was readily spread by cultivation and detrimentally changed the suitability of once prime agricultural land for crops (Parsons & Cuthbertson 2001).

How To Manage It?

Best practice management

Hoary Cress (Lepidium draba) can spread by both seed and more commonly via root fragments although most new plants arise from its spreading roots and broken root segments. Integrated control of Hoary Cress  includes prevention, education, early detection and eradication. Prevention is essential in preventing further outbreaks and spread.  Most successful control efforts combine several management techniques such as herbicide application and physical removal by cultivation, followed by competitive species plantings (Lyons 1998). Its impact was largely curtailed through the incorporation of longer pasture phases in cereal cropping rotations and through the use of more effective herbicides (Faithfull 1998; Parsons & Cuthbertson 2001).

Chemical control: Herbicides can be used successfully in controlling Hoary Cress. Timing of herbicide applications is critical in achieving desirable results and several years of treatments may be required (DPIW 2002). Numerous treatments area available, see CABI 2021; DPI NSW (2019) Herbiguide (2021).

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

Non-chemical control: Physical control: Not normally effective as roots with buds left in the soil will re-sprout and regrow. 

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Seeds of Hoary Cress (Lepidium draba) germinate during autumn and seedlings grow into rosettes during winter and spring. Plants grown from seed generally do not flower in the first year. However, flowering shoots arise in successive autumns from the perennial root system that was formed (Agriculture Western Australia 2005). Erect flowering stems are formed in late winter to early spring and plants flower from September to November. Stems die down in summer but the perennial roots become dormant until the following autumn and spring. If plants are disturbed by cultivation in spring or summer, new rosettes are usually formed out of season (Agriculture Western Australia 2005; Parsons & Cuthbertson 2001; DPIW 2002). Seeds can remain viable for three or four years and lack long-term dormancy (Faithfull 1998).

Where Is It Found?

Which states and territories is it found?

NSW, QLD, SA, TAS, VIC, WA

What areas within states and territories is it found?

Hoary Cress (Lepidium draba) occurs widely throughout the cereal growing areas of New South Wales and Victoria, and the northern wheat belt of South Australia. It is also an important weed on alluvial river flats in several vegetable growing areas of New South Wales. In Tasmania, Hoary Cress is common in the south-eastern and Midlands areas and occurs occasionally in the north of the state. Populations are increasing in the Midlands and Derwent Valley, especially where it occurs along roadsides (Parsons & Cuthbertson 2001; DPIW 2002). There are only isolated patches in south east Queensland, where it mainly occurs on the Darling Downs and in the Lockyer Valley. In Western Australia, a small number of infestations are known from the Avon Wheatbelt, Esperance Plains and the Mallee regions (Parsons & Cuthbertson 2001).

Where does it originate?

Hoary Cress originated in the area extending from the eastern Mediterranean through Asia Minor to southern and central Asia (Parsons & Cuthbertson 2001).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

NSW, SA, TAS, VIC, WA

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Lepidium draba

Other scientific names (synonyms)?

• Brassica tenuifolia (L.) Fr.
• Sisymbrium tenuifolium L.

Does it have other known common name(s)?

White Weed, Hoary Pepperwort