Sisymbrium officinale (L.) Scop
hedge mustard, tumbling mustard, oriental mustard, wild mustard, Indian hedge mustard, oriental rocket mustard, mustard, oriental rocket, common hedge mustard, english water cress, erysimum, thalictroc
A bristly, annual or biennial (lasting 2 years) herb with a rosette or deeply divided leaves with toothed margins with a much larger rounded terminal lobe that grows to 90cm high. The stems are wiry with pale yellow terminal flowers.
A weed of agricultural areas in eastern and southern Australia. Hedge mustard is a common weed of wasteland, roadsides, cultivation and disturbed habitats and is suspected of tainting milk.
Stems and Leaves:
The stem is wiry with very short internodes. Basal leaves form a deeply divided rosette (a cluster of leaves at the base of a plant often lying flat against the ground). The basal (lower) leaves are up to 10cm long, pinnatisect (cut into lobes on both sides of the midrib to or almost to the midrib) with 3-5 pairs of toothed lobes and a large terminal lobe petiolate (with a leaf stalk). Middle and upper stem leaves are smaller, with or without a short petiole, much less divided, alternate (1 leaf per node). The whole plant often appears grey-green in appearance.
Flowers and Fruit:
The flowers are small and in racemes (a simple inflorescence in which the flowers are stalked) with four yellow to pale yellow petals that are 2-4mm long, in the shape of a cross. The inflorescence has no bracts. There are 4 free sepals that are 2mm long, 4-6 stamens, the inner four being longer than the outer pair. The fruits is a conical shaped siliqua (a dry dehiscent fruit three times as long as broad) 1-2cm long, without a beak, held close to the stem on a short stout pedicel (stalk) 1-2mm long. It is dehiscent (opens at maturity to release the contents) with 2 valves, each with several seeds which are about 1.5mm long.
All plants in the genus Sisymbrium have fruit (siliqua) without a beak and the seeds are in one row. For S. officinale, the fruit is held tightly alongside the stem and is only 1-2cm long. It is supported by a short, stout pedicel (stem). The whole plant is rough to the touch and is wiry when dry. Often the branches of the mature inflorescence are rigid and spread at right angles to the main axis. The plant has a grey-green appearance.
For S. irio (London rocket) and S. orientale (Wild Mustard) both of which grow in the Sydney region, the siliquas (fruit) spread away from the inflorescence branch.
Sisymbrium irio has curving siliquas 3-5cm long and markedly constricted between the seeds.
Sisymbrium orientale has longer siliquas 6-12cm long that are orientated at almost right angles to the inflorescence (flowers) branch.
Sources & References
Auld BA, Meld RW (1992) 'Weeds an illustrated botanical guide to the weeds of Australia.' (Inkata Press: Melbourne)
Carolin R, Tindale MD (1993) 'Flora of the Sydney region.' (Reed: Chatswood, Australia)
Cunningham GM, Mulham PL, Leigh JH (1981) 'Plants of Western New South Wales.' (NSW Government Printing Office: Australia)
Harden GJ (Ed) (2002) 'Flora of New South Wales.' (University of New South Wales Press Ltd: Sydney, Australia)
Muenscher WC (1980) 'Weeds.' 2nd edn. (Cornell University Press: London)
Plants for a Future- Species Database (2000) www.ibiblio.org
Tamar Valley Weed Strategy (2004) www.weeds.asn.au
Prepared by Kylie Pethybridge, 2005
Checked by Carole Campbell, 2005
Updated by Justin KY Chu, July 2005
Checked by Dr Peter Michael, July 2005