Coronopus is the Greco-Latin name for a cress like plant and is from the Greek words korone meaning crow or something curved like a crows beak and pous meaning foot and refers to the crows foot like leaf arrangement.
Lesser Swinecress
Other names:
Bitter Cress
Lesser Wart-cress
Twin Cress
Summary:
A foul smelling, lobed leafed, spreading or semi-erect annual to perennial plant with fruits that look like dog balls that are produced from inconspicuous flowers in spring.
Description:
Cotyledons:
Two. The cotyledon is 7 to 12 mm long overall with a merging petiole, and is hairless. The seedling has a short hypocotyl and no epicotyl.
First leaves:
The first leaves, which develop singly, are 12 to 20 mm long overall of which about half is petiole. The leaves are hairless. The first leaf has a simple margin or only small lobes.
Leaves:
The plant forms a rosette some 200 mm in diameter. Later leaves become increasingly lobed and ultimately pinnate. Distinctive 'cress' smell when crushed.
Petiole - Yes.
Blade - Lobed to pinnate, with 3-5 pairs of deep lobes that are narrow and smooth edged or with cut segments. 6-25 mm long by4-12 mm wide. Hairy or hairless.
Stem leaves - Pinnate with a short petiole, and hairless. Becoming stalkless and without lobes towards the top of the stem.
Stems:
The stems are prostrate, spreading or semi erect, and reach 400 mm or more in length. They are much branched, solid, fluted or circular in cross section with longitudinal grooves. The young stems carry long thin, curved or curled, white hairs and become hairless with age. They sometimes form mats and tend to be darker in colour on the upper side.
Flower head:
Raceme that appears terminal and later lateral opposite leaves but not in the axil (according to Burbidge, others call it axillary). The raceme is longer than the leaf that it is opposite. Raceme lengthens as the fruit develops to reach up to 60 mm long.
Flowers:
Very small, 1.5-2 mm in diameter.
Ovary - Sessile stigma.
Sepals - 0.5-2 mm long, sometimes hairy outside, with a white edge.
Petals - 4, white, shorter than sepals. Sometimes absent.
Stamens - 2 fertile stamens.
Anthers -
Fruit:
Distinctive double sphere shape pod, constricted at the centre, notched at the top and base, 2-4 mm wide by 1.5 mm long. Separates at maturity into 2 egg shaped nutlets. On a hairy, curved stalk, 1.5-3 mm long and longer than the pod.
Seeds:
Egg shaped nutlet, network wrinkled or pitted, single seeded, 1-2 mm diameter, seed remains inside the nutlet (indehiscent).
Roots:
Key Characters:
Fruiting raceme longer than the leaf. Pod bilobed.
Biology:
Life cycle:
Annual, biennial or perennial. The main germination occurs in autumn with some in spring. It grows rapidly from autumn and spring
Physiology:
Reproduction:
By seed.
Flowering times:
September to January in SA.
Mainly September to December in Perth.
Seed Biology and Germination:
Vegetative Propagules:
None.
Hybrids:
Allelopathy:
Population Dynamics and Dispersal:
Spread by seed.
Origin and History:
Mediterranean or temperate South America.
Distribution:
ACT, NSW, QLD, SA, TAS, VIC, WA.
Lesser Swinecress occurs throughout Tasmania.
Habitats:
Climate:
Temperate.
Higher rainfall areas.
Soil:
Plant Associations:
Significance:
Beneficial:
Eaten by stock.
Stems and leaves eaten by man.
Detrimental:
Weed of disturbed areas, arable crops, cultivation, gardens, lawns and pastures.
Especially troublesome during the establishment stage of pastures but tends to persist only in weak established pasture.
It is a major cause of taint in milk.
Taints meat.
Toxicity:
Not recorded as toxic.
Legislation:
None.
Management and Control:
Thresholds:
It is a moderately competitive species.
Eradication strategies:
Most of the Brassicaceae weeds have dormant seeds that continue to germinate throughout the season and for several years. They often mature and set seed very quickly. Manual removal is effective but must be done at least every 8-10 weeks. Once pods are formed, seed will often mature even if the plant has been uprooted. Soil disturbance often leads to a flush of seedlings.
Many are somewhat unpalatable, so grazing only offers partial control. They often flourish in undergrazed, sunny areas.
In bushland situations, fairly selective control can be achieved with 100 mL spray oil plus 0.1 g Eclipse® or 0.5 g Logran® in 10 L water. 5 mL Brodal® is often added to this mix to provide residual control of seedlings. Spray the plants until just wet from the seedling stage up to pod formation.
Isolated plants should be removed manually and burnt if flowering or seeding and a 10 m buffer area sprayed with 10 mL Brodal® in 10 L water.
500 mL/ha of glyphosate(450g/L) can be used at flowering to reduce the seed set of most species on roadsides without causing significant damage to most native plants.
Wick application with 1 part glyphosate(450g/L) in 2 parts water or overall spraying with 100 mL glyphosate(450g/L) in 10 L water provides reasonable control of most species though Wild Radish tends to regrow.
Herbicide resistance:
Biological Control:
Related plants:
Swinecress (Coronopus squamatus) is very similar but the fruit does not split into 2 nutlets when mature and the flowering structure is shorter than its opposite leaf.
The native Brassicaceae species usually have short, broad and smooth pods.
Plants of similar appearance:
Lesser Swinecress is difficult to distinguish from Cotula except when seed or flowers are present. The 'cressy' smell of Swinecress is distinctive, as are the small cotyledons of Cotula if present, but these do not usually persist. Though generally very similar there are differences in leaf shape; the terminal leaflet of Cotula often has three lobes while that of Swinecress is often single, and the leaflets on Cotula are usually pinnately lobed while the leaflets of Swinecress tend to have lobes on one side only and not pinnately paired lobes.
References:
Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P133. Photo.
Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P387. Diagram.
Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P187-188. Diagram.
Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P321-322. Photo.
Hyde-Wyatt, B.H. and Morris, D.I. (1975). Tasmanian weed handbook. (Tasmanian Department of Agriculture, Hobart, Tasmania). P43. Diagram.
Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).
Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #354.1.
Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P164.
Acknowledgments:
Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.