Yellow Serradella is a sprawling, low growing, grey-hairy legume. The leaves have 7-18 pairs of narrow leaflets. It has stalked head-like clusters of small yellow, 6-8 mm long pea flowers in early summer. The pods are rather straight and flattened and break up at maturity into single-seeded units.
It is native to Europe or the Mediterranean region and has become a widespread weed along roadsides and particularly in wetlands. Slender
Description:
Cotyledons:
Two.
Leaves:
With 7-18 pairs of leaflets.
Stipules - Small and membranous on the main leaf, no stipules on the leaflets.
Petiole - On the main leaf only.
Blade - Leaflets, narrowly oblong to oval, 2-10 mm long by 1-4 mm wide, edges smooth, hairy on both sides, rounded or pointed tip.
Stems:
Low lying, sprawling or bending upwards at the ends, 300 mm long. Hairy.
Flower head:
On stalks in leaf axils, 2-5 flowered. With a floral leaf with leaflets underneath.
Flowers:
Yellow, pea type.
Bracts - Tiny
Ovary - Stalkless. Many ovules. Style bent inwards, Stigma flat topped.
Sepals - 4-5 mm long, tubular ribbed near the base, 5 narrowly triangular lobes on top about 2-2.5 mm long with acute tips. Lobes of the upper lip shortly joined. Tube is 2-2.5 mm long. Densely hairy.
Petals - Yellow, joined to the sepal tube. Standard 6-7.5 mm long. Limb egg shaped. Wings ~5 mm long. Keel 3-5 mm long.
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. Sparsely hairy or with short hairs. Scarcely or not constricted between the seeds. 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 yellow. Calyx lobes 2-2.5 mm long and as long as the tube. Pod not or only scarcely 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 early summer and die with the onset of high temperatures and summer drought.
Physiology:
Fixes atmospheric nitrogen.
Reproduction:
By seed.
Flowering times:
November in Perth
Early summer in WA.
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:
French Serradella (Ornithopus sativus) is a hairy plant with pink or white flowers and a narrow but very compressed pod which is distinctly constricted between the seeds. It is currently naturalised around Esperance and will become more widespread with agricultural plantings.
Slender Serradella (Ornithopus pinnatus) is almost hairless with yellow flowers and a narrowly cylindric seed pod and also widespread in WA..
Yellow Serradella (Ornithopus compressus) - has yellow flowers and pods scarcely constricted between the seeds.
Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne).
Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia).
Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).
Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).
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. Photo.
Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).
Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #728.1.
Marchant et al (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P288.
Parsons, W.T. and Cuthbertson, E.G. (1992) Noxious weeds of Australia. (Inkata Press, Melbourne).
Acknowledgments:
Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.
