Form: herbaceous — perennial
Status: present in WA
Erect perennial herb 15-75 centimetres high, native of eastern Mediterranean and to central and southern Asia. It reproduces from seed, and from shoots from the perennial roots.
Stem: upright, branching near the top, covered with fine downy hairs, and longitudinally ribbed.
Leaves: leaves grey-green, covered with fine white hairs. Rosette and lower stem leaves up to ten centimetres long, oval to long-triangular and stalked; upper stem leaves up to eight centimetres long, alternate and oval with the narrow end attached.
Flowers: white, four to six millimetres in diameter, four petalled in dense terminal clusters; fragrant. Numerous flowers appear from September to November, in clusters at the tops of the stems.
Fruit: heart-shaped capsule two to four millimetres long, three to five millimetres wide, containing one or two seeds.
Seed: reddish brown, oval, about two millimetres long.
Spreads by movement of root sections and by seed. Regrows from perennial rootstock and from root fragments. Plants may produce up to 5000 seeds with high viability, although most spread is by movement of pieces of root during soil cultivation. Germinates in autumn and winter. In some locations in New South Wales, Victoria and South Australia it has been a major weed of many crops, including cereals and vegetables. In Tasmania it is a major weed of roadsides, railway lines and run-down pasture. In Western Australia it is a target for eradication.
Online weed identification training
Login or set up a new account on DPIRDs online training site to access:
- a training course on how to identify hoary cress and report it.
- training material that you can use to teach community groups how to identify hoary cress.
Agricultural and economic impact
Hoary cress can invade pastures, grain crops and horticultural crops. It has a very competitive deep perennial root system and can be allelopathic. It can taint milk and meat if grazed. Being in the cabbage family (Brassicaceae), it is likely to harbour diseases and pests that could attack canola and cruciferous vegetables.
Modelling indicates that hoary cress would cost Western Australia $6.2 million each year if it is not managed and $5.5 million if it is managed (Cook, D. 2014. Agricultural Resource Risk Management. Strategic Report. Impact Assessments for Declared Plants in Western Australia. July 2014, Department of Agriculture and Food, Western Australia)
Declared pest category
The Western Australian Organism List (WAOL) contains information on the area(s) in which this pest is declared and the control and keeping categories to which it has been assigned in Western Australia (WA). Use the following WAOL link to reach the declaration and declaration map for hoary cress.
Requirements for land owners/occupiers and other persons
Requirements for land owners/occupiers and other persons if this pest is found can be sourced through the declared pest plant requirements link.
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Pest and Disease Information Service (PaDIS)
Detectability: medium difficulty to find. Hoary cress can be distinguished by its greyish stems and leaves, and its many small white flowers carried at the shoot tips.
Who should look for it: grains industry, and horticulturists including orchardists, viticulturists and vegetable growers, biosecurity groups, landholders who have infestations of this weed, and other landholders in the vicinity of known infestations.
When to find it: hoary cress is most conspicuous when mature plants are flowering in spring and summer, with peak flowering in October-November. It persists over the rest of the year below-ground.
Where to find it: in WA hoary cress has been found occasionally in the Wheatbelt, but most infestations have been eradicated. In other parts of Australia and in other countries, hoary cress infests grain crops, horticultural crops, roadsides and railway lines.
Report the presence of this organism before undertaking a control measure. Control methods for this declared plant can be found through the hoary cress control link.
Further information on hoary cress can be found on the hoary cress: what you should know page.