Hexham Scent

Melilotus indica (L.) All.

Synonyms - Melilotus indicus, Melilotus parviflora.

Family: Fabaceae.

Names:

Melilotus is from the Greek meli meaning honey and lotos meaning lotus.
Hexham Scent.

Other names:

Annual Yellow Sweet Clover
Bokhara Clover
Californian Lucerne
Common Melilot
Hexham scented Melilot
Indian Clover
King Island Clover
King Island Melilot
Melilotus
Senji
Small Melilot
Sweet Melilot
Sour Clover

Summary:

Usually erect, almost hairless, often smelly, annual to biennial legume about 50 cm tall with trifoliate leaves with the central leaflet on a longer stalk, angular stems and clusters of small, yellow, pea type flowers in spikes in spring.

Description:

Cotyledons:

Two. Oval. Tip rounded. Sides convex. Base tapered. Surface hairless. Petiole shorter than the blade.

First leaves:

The first leaf is heart shaped with a notched tip and is hairless. The second and next few leaves have 3 heart shaped, smooth edged leaflets. Later leaves have more elongated leaflets with toothed edges.

Leaves:

Alternate. Three leaflets with the central leaflet on a longer stalk than the 2 side leaflets. Usually with a strong vanilla like odour when crushed.
Stipules - Narrow and tapering to a fine point. Edges smooth or with one or two teeth near the base. Attached to the petiole.
Petiole - Long, commonly 10-40 mm.
Blade - Of leaflets, egg or wedge shaped to oval, 5-30 mm long x 3-15 mm wide. Tip is flat to notched and often with a fine flexible point. Edges finely serrated. Base tapered to squarish. Surface hairless on top, sparsely hairy underneath and the central vein is often red.
Upper leaves narrower.

Stems:

Erect, spreading or sprawling. 100-1000 mm tall, angular. Almost smooth and hairless.

Flower head:

Dense, narrow raceme, 10-40 mm long on an erect stalk that is 10-30 mm long and arises from the leaf axils.

Flowers:

Yellow, pea type, small, 2-3 mm long.
Ovary - 2 ovules.
Calyx - Tubular. Tube is 0.5-1 mm long, hairless, with triangular lobes that are 0.5-1.5 mm long.
Petals - Yellow, free, fall when mature. Standard 2.5-3 mm long x 1-1.5 mm wide. Limb narrowly egg shaped. Keel 2-2.5 mm long, blunt.
Stamens - 9 united plus 1 by itself.
Anthers -

Fruit:

Olive green, leathery pod, swollen or slightly flattened, egg shaped to almost globular, 2-3 mm long x 1.5-2 mm wide, with a network of veins to being deeply wrinkled. The pod is on a pendulous short stalk. 1-2 seeds per pod. Does not open to drop seeds when it falls at maturity.

Seeds:

Globular, flattened, 1-2 mm diameter with a depressed or somewhat grooved face. Surface pimply and hairless with a white stripe (aril).

Roots:

Short taproot and many spreading laterals with nitrogen fixing nodules.

Key Characters:

Trifoliate leaves with the central leaflet on a longer petiolule than the side leaflets.
Raceme 10-40 mm long and longer than the leaves. Calyx 5 nerved. Yellow flowers 2-3 mm long on long, 10-60 mm peduncles. Pod 2-4 mm long, obtuse and reticulate to rugose.

Biology:

Life cycle:

Annual or biennial. Seeds germinate in autumn and winter and it grows mainly in spring but continues through summer in moist areas. It flowers from late winter to early summer.

Physiology:

Coumarin causes the odour.

Reproduction:

By seed.

Flowering times:

Late winter to early summer in western NSW.
August to November in SA.
Mainly August to October in Perth.
Mainly August to November in WA.

Seed Biology and Germination:

Seed remains viable in the soil for some years.

Vegetative Propagules:

None.

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Spread by seed.

Origin and History:

Mediterranean. Southern Asia.

Distribution:

ACT, NSW, NT, QLD, SA, TAS, VIC, WA.

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Temperate. Mediterranean.

Soil:

Most abundant on sandy soil, near the sea, lake margins, river banks, on limestone soils, heavy grey clay and granite outcrops.
Moist areas.

Plant Associations:

Open Mitchell grass, Black Box, Mallee and many other communities.

Significance:

Beneficial:

Relatively unpalatable fodder, eaten mainly when young.
Salt tolerant and used for reclamation.
Used as a green manure crop in the USA.
Cultivated as a fodder crop in India.

Detrimental:

Weed of roadsides, cultivated areas, pastures, hay, crops, coastal islands, coastal woodlands, granite outcrops, and disturbed areas.
Seed is a prohibited impurity of wheat for human consumption.
Contains coumarin, which taints meat, eggs, dairy products, hay, flour and bread. The taint from Hexham scent seeds is transferred to wheat, oats and barley and removal of the weed seed before milling does not prevent the flavour coming through in the flour, bread or biscuits.

Toxicity:

Possibly toxic but unconfirmed.

Symptoms:

Lethargy and paralysis prior to death.

Treatment:

Don't graze milking cows or stock for slaughter on infested areas.

Legislation:

Seed is a prohibited impurity of wheat for human consumption.

Management and Control:

Cultivation controls seedlings. Prevent seed set by heavy grazing with animals not destined for slaughter. Hormone herbicides are effective on young actively growing plants. If present at harvest, weed seed should be removed from the grain without delay. Seed remains viable in the soil for some years so repeated control over a number of seasons is required.

Thresholds:

Low numbers can cause grain contamination or taint milk and meat products.

Eradication strategies:

Isolated plants can be removed manually. Small infestations in grassed areas can be treated annually in late winter by spraying with 1 part of Tordon® 75-D in 100 litres of water. Larger infestations can be cropped with cereals and treated with sulfonyl urea herbicides.

Herbicide resistance:

Biological Control:

Related plants:

Bokhara Clover (M. albus) has white flowers and is usually larger and more robust.
Messina Melilot (M. messanensis) has larger 5-6 mm long flowers.
Yellow Sweet Clover (M. officinalis) has larger 5-6 mm long flowers.

Plants of similar appearance:

Lucerne (M. sativa) looks similar but has purple flowers and little odour when crushed and is perennial.
Clovers, Trefoils, Oxalis spp., Lotus, Medics.

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P168. Photo.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P456. Diagram.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P223. Diagram.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P406. Photo.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P474.

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). P154-156. Photo.

Hyde-Wyatt, B.H. and Morris, D.I. (1975). Tasmanian weed handbook. (Tasmanian Department of Agriculture, Hobart, Tasmania). P103-104. Diagram of leaf.

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). #811.2.

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). P285.

Meadly, G.R.W. (1965). Weeds of Western Australia. (Department of Agriculture - Western Australia). P95. Diagrams. Photo.

Wilding, J.L. et al. (1987). Crop weeds. (Inkata Press, Melbourne). p107. Diagram. Photos.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.