Barrel Medic

Medicago truncatula Gaertner

Synonyms - Medicago tribuloides var. truncatula, Medicago tentaculata.

Family: Fabaceae.

Names:

Medic is from the Latin medica meaning Lucerne and derived from the Greek mediche because it was introduced to Greece from the Media region in the Old Persian Empire.
Barrel medic refers to the barrel shape of the coiled seed pod.

Other names:

Barrel Medick
Cylindrical Burr Medic
Caltrop Medic
Trefoil

Summary:

A softly hairy, prostrate annual with stems to 300 mm long, alternate trifoliate leaves, yellow pea type flowers and a barrel shaped pod or burr.

Description:

Cotyledons:

Two. Club shaped. Tip round. Sides convex. Base tapered. Surface hairless. Petiole shorter than blade and merging with it.

First leaves:

The first leaf is round with a toothed edges and fine hairs on both surfaces of the blade and petiole. Later leaves have 3 leaflets.

Leaves:

Alternate. Three leaflets with the middle leaflet larger than the other two and on a longer stalk.
Stipules - Attached to petiole, deeply toothed.
Petiole - Long and hairy.
Blade - Of leaflet, oval or wedge to diamond shaped, 8-15 mm long x 7-12 mm wide, margin coarsely toothed. Tip blunt or rounded to flat. Base tapered to squarish. Short soft hairs. It sometimes has a brown blotch in the centre of the leaflets.

Stems:

Prostrate or bending upwards at the ends, square, 150-300 mm long. Short soft hairs.

Flower head:

1-4 flowers in a cluster, on an awned axillary stalk shorter than that of the leaves. Axillary raceme.

Flowers:

Yellow, pea type, 6-8 mm long.
Bracts - Small, persistent.
Ovary -
Calyx - 5 teeth.
Petals - Yellow.
Stamens - 9 in a group and 1 alone.
Anthers -

Fruit:

Barrel shaped pods with 4-5 compact coils, 7-12 mm long x 6-7 mm diameter. Short, straight, thick spines, 2 mm long, that tend to lay against the pod. No terminal hooks on the spines but this may vary with variety. Hairy or hairless.

Seeds:

Kidney shaped, 3-3.5 mm long. 1-2 seeds per coil of the pod.

Roots:

Taproot. Has nitrogen fixing nodules.

Key Characters:

Cotyledons club shaped.
First leaf round shaped.
Older leaves trifoliate with the terminal leaflet on a longer petiolule than the side leaflets.
Stipules toothed.
Hairy stems.
Yellow pea type flowers.
Barrel shaped pod, flat at both ends with 4-6 compact coils and membranous partitions between the seeds. The transverse nerves of the pod terminate in a nerve parallel to and on each side of the dorsal suture. Spines are grooved towards the base pressed against the pod.
Kidney shaped seed.
Annual.

Biology:

Life cycle:

Annual. Germinates in autumn and winter and produces large amounts of herbage in winter and spring. Flowers in spring and dies with the onset of high temperatures and summer drought.

Physiology:

More drought tolerant than subterranean clover.

Reproduction:

By seed.

Flowering times:

Flowers September to November in SA.
Spring in western NSW.
Spring in WA.

Seed Biology and Germination:

Produces large quantities of normal and hard or dormant seed.

Vegetative Propagules:

None.

Hybrids:

A number of varieties exist that vary in the spininess of the pod and their flowering times.
Variety truncatula is the most common. Var. longispina has disk like burrs, 6-10 mm long and they are shorter than their width, and have curved spreading spines about 4 mm long.

Allelopathy:

Population Dynamics and Dispersal:

Initially, the main spread was due to intentional planting. Now the spread is mainly by burrs attaching to passing animals thereby distributing seed.
The time from germination to flowering varies from 9-15 weeks depending on the variety.

Origin and History:

Mediterranean.

Distribution:

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

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Temperate. Mediterranean.
Most common in areas with an annual rainfall of 250-400 mm.

Soil:

Most abundant on alkaline soils such as the self mulching clays, calcareous red earths, red brown earths and heavy grey clays.
Occurs on a wide range of other soils.

Plant Associations:

In many communities.

Significance:

Beneficial:

Important pasture species especially on the light alkaline soils.
Produces palatable, high quality forage during the growing season. Burrs provide high quality feed over the dry periods.
Fixes nitrogen.

Detrimental:

Weed of crops, fallows, roadsides and disturbed areas.
Burrs contaminate wool causing vegetable fault.

Toxicity:

May cause oestrogenic effects or "clover disease" in livestock.

Symptoms:

Reduced fertility, difficult birth and prolapse of the uterus in ewes.
Urinary obstruction and milk production in wethers.

Treatment:

Remove stock from pure stands or supply alternative feed.

Legislation:

None.

Management and Control:

Thresholds:

Eradication strategies:

Small infestations in grassed areas can be controlled by annual applications of 1 part Tordon® 75-D in 100 parts of water. Sulfonylurea herbicides are also very effective.

Herbicide resistance:

It is relatively tolerant to glyphosate.

Biological Control:

Related plants:

Barrel Medic. (M. truncatula)
Black Medic (M. lupulina)
Burr Medic (M. polymorpha)
Button Medic (M. orbicularis)
Calvary Medic (M. intertexta)
Cutleaf Medic (M. laciniata)
Disc Medic (M. tornata)
Gama Medic (M. rugosa)
Lucerne (M. falcata ssp. sativa)
Lucerne (M. sativa)
Small leaved Burr Medic (M. praecox)
Snail Medic (M. scutellata)
Spotted Medic (M. arabica)
Strand Medic (M. littoralis)
Woolly Burr Medic(M. minima)
Yellow Lucerne (M. falcata)
Spineless Burr Medic (M. polymorpha var. brevispina) has no spines and radiating veins on the coil surface that are strongly curved, fine and close.

Plants of similar appearance:

Clovers (Trifolium species) usually have the central leaflet on a stalk the same length as the side leaflets.
Melilotus species
Oxalis species usually have a bitter taste.
Trefoils

References:

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P459.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P405.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P490.

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.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne). p106.

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #806.18.

Wilding, J.L. et al. (1987). Crop weeds. (Inkata Press, Melbourne). P106. Diagrams. Photos.

Acknowledgments:

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