A low growing, sprawling, hairy annual legume with leaves divided into 5-18 pairs of narrow leaflets. It has stalked head-like clusters of pink to white pea flowers in spring. The flowers are white to pink and 6-8 mm long in spring. The seed pods are straight or slightly curved, narrow but very compressed and distinctly constricted between the seeds to almost like a string of beads and separate at maturity into single-seeded units.
Native to Europe or the Mediterranean region but have become weeds along roadsides, particularly in wetlands.
Description:
Cotyledons:
Two.
Leaves:
With 5-18 pairs of leaflets.
Stipules - Small and membranous on the main leaf, no stipules on the leaflets.
Petiole - On the main leaf only.
Blade - Leaflets, oval, 3-10 mm long by 1.5-4 mm wide, sides convex, sparsely hairy, rounded tip with a tiny point.
Stems:
Low lying, sprawling or bending upwards at the ends, 500 mm long. Hairy.
Flower head:
On stalks in leaf axils, 2-5 flowered. With a floral leaf with leaflets underneath.
Flowers:
Pink or white, pea type.
Bracts - Tiny
Ovary - Stalkless. Many ovules. Style bent inwards, Stigma flat topped.
Sepals - 4 mm long, tubular ribbed near the base, 5 narrowly triangular lobes on top about 2 mm long with acute tips. Tube is 2 mm long. Hairy.
Petals - Pink or white. Standard 7-8 mm long. Limb narrowly oblong or egg shaped. Wings 5-6 mm long. Keel 3-4 mm long, straight, obtuse tip.
Stamens - In 2 groups. Filaments of each group joined. Alternate filaments swollen near the tip.
Anthers - All the same.
Fruit:
Very flattened, narrowly oblong pod, 10-25 mm long, stalkless with a network pattern on the surface. Straight or slightly curved. Hairless or with short hairs. Constricted between the seeds to almost like a string of beads. Pod does not release seed when ripe, it breaks crosswise into single seeded segments.
Seeds:
No persistent enlarged seed stalk (funicle or aril) where the seed joins the pod.
Roots:
Taproot and laterals with nitrogen fixing nodules.
Key Characters:
Hairy. Annual. Flower head subtended by a pinnate floral leaf. Flowers pink or white. Calyx lobes 2-2.5 mm long and as long as the tube. Pod distinctly constricted between the segments.
From Judy Wheeler, Flora of the Perth Region.
Biology:
Life cycle:
Annual. Seeds germinate in autumn and the plant grows through winter and spring to flower in October and die with the onset of high temperatures and summer drought.
Physiology:
Fixes atmospheric nitrogen.
Reproduction:
By seed.
Flowering times:
October in Perth.
Seed Biology and Germination:
Produces hard or dormant seed.
Seed may need scarification to achieve high germination levels.
Vegetative Propagules:
None.
Hybrids:
Allelopathy:
Population Dynamics and Dispersal:
Spread by seed. Passes through stock in a viable condition.
Weed of crops, roadsides, bushland and disturbed areas.
Toxicity:
Not recorded as toxic.
Legislation:
None.
Management and Control:
Thresholds:
10-30 plants/m2 are usually worth spraying in grass or cereal crops.
Eradication strategies:
Exclude stock to reduce the dispersal of seed.
Hand pull odd plants in winter before flowering. For small infestations and grass dominant areas an annual application of 10 mL Tordon®75-D in 10 L water in early winter gives excellent control of existing plants and has residual activity to control later seedlings. 200 mL/ha Lontrel®750 or 50 g/ha Logran® applied in early winter provides reasonably selective control in bushland areas. For hand spraying use 25 mL wetting agent plus 4 g Lontrel®750 or 1 g Logran® in 10 L water. Repeat annually for several years. Metsulfuron(600g/kg) also provides good control at 5 g/ha but is less selective.
Plant tall growing perennial species to reduce re-invasion.
It is relatively tolerant to glyphosate, grazing and mowing.
Other sulfonylurea herbicides also provide good control.
Herbicide resistance:
Relatively tolerant to glyphosate and bipyridyl herbicides.
Biological Control:
Related plants:
Slender Serradella (Ornithopus pinnatus) is almost hairless with yellow flowers and a narrowly cylindric seed pod. It is widespread in WA.
Yellow Serradella (Ornithopus compressus) is a greyish hairy plant with yellow flowers and a narrow but compressed seed pod but scarcely constricted between the seeds. . It is widespread in WA.
Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P156.
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). #909.3.
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). P288.
Acknowledgments:
Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.
