Subterranean Clover

Trifolium subterraneum L.

Synonyms - Trifolium subterraneum ssp. yanninicum.

Family: Fabaceae.

Names:

Trifolium is from the Latin tres meaning 3 and folium meaning leaf and refers to the 3 leaflets.
Subterraneum refers to seed burying behaviour of the plant.
Subterranean Clover

Other names:

Clover
Sub clover

Summary:

A hairy, low lying, annual clover with trifoliate leaves with various markings. The small, white and pink flowers appear in late winter to spring and produce globular burrs that are usually buried in the soil.
Native to Europe and the Mediterranean region, it flowers in late winter and spring.

Description:

Cotyledons:

Two. Oval, 4-5 mm long x 2-3 mm wide. Tip rounded. Sides convex. Surface hairless. Petiole slightly longer than the blade or 4-6 mm long.

First leaves:

Round to kidney shaped 5 mm long. Leaf stalk 10 mm long. Hairy. Tip pointed.

Leaves:

Alternate. 3 leaflets.
Forms a rosette 150-300 mm wide.
Stipules - Membranous to leafy, 5-15 mm long, broadly egg shaped with tapering tips. Fused to stem. Free part oblong to triangular.
Petiole - As long or longer than leaflets and hairy.
Blade - Of leaflet, heart shaped to round or egg shaped leaflets, sometimes with fine teeth near the tip, 4-22 mm long x 4-23 mm wide. Tip usually notched. Hairy. Has a variety of brownish and white markings depending on the cultivar. Leaflet stalks are all the same length.

Stems:

Low lying, branched, up to 1000 mm long, solid, pithy core, round or fluted. Hairy.

Flower head:

At the ends of slender stalks (peduncles) in leaf axils that turn toward the ground after flowering. 3-8 white or pink outer fertile flowers and several barren inner ones without petals that bend back with age so fertile flowers are surrounded by enlarged rigid barren calyxes with spreading teeth to forma a burr that is usually buried in the soil.

Flowers:

Pea type fertile flowers and tubular sterile flowers with no petals. Stalkless (no pedicels).
Ovary -
Calyx - 6-10 mm long. Tube 3-4 mm long, hairless or sparsely hairy with a ring of hairs inside, often red near the top. 5 almost equal, thread like lobes 3-6 mm long, longer than tube with bristles. Many veined when in fruit.
Petals - White to pink, narrow, 6-11 mm long. Standard twice as long as calyx. Limb of standard oblong, rounded to notched. Keel slightly shorter than the wings with an obtuse tip.
Stamens - 10 with 9 in a group.
Anthers -

Fruit:

3-8 pods in s a burr. Pods brown, hard, net veined pods, circular to oblong in outline, 3 mm long, containing 1 (rarely 2) seeds per pod. Hidden by solid, sterile, bent back, inflated flowers that form the burr. The burr is usually buried in soil.

Seeds:

Round to oval, black or dark, 1-3 mm long. The yanninicum subspecies (eg cultivars Yarloop, Trikkala, Larisa and Meteora) have white to cream seed.

Roots:

Taproot. Has nitrogen fixing nodules on taproot and laterals.

Key Characters:

Few fertile, white to pink, sessile flowers in head, barren ones bristle like. Peduncles recurved in fruit. Calyx not bladdery or inflated, indistinctly veined and hairy on lobes, not recurved but sometimes spreading in fruit. Lobes linear, subulate, setaceous, or filiform and usually 3-9 mm long. Throat of calyx slightly closed usually hairy inside with a denser ring of hairs. Inner sterile flowers developing after fertilisation causing the pods to become buried underground.
Pod with 1-2 seeds, less than 4 mm long, enclosed in and concealed by the calyx.
Leaflet stalks are all the same length.
Entire stipules.

Biology:

Life cycle:

Annual. Germinates autumn to spring. Flowers late winter to spring.

Physiology:

Germination to flowering may take from 22 to 36 weeks depending on the cultivar.
It is not very palatable until the flowering stage, which allows it to persist better under grazing.
Has symbiotic rhizobia in nodules on the roots that fix atmospheric nitrogen.

Reproduction:

By seed.

Flowering times:

Spring to early summer in western NSW.
October to December in SA.
August to November in Perth.
Winter and spring in WA.

Seed Biology and Germination:

Hard seeded.

Vegetative Propagules:

None.

Hybrids:

Hybrids can be produced and many commercial varieties are available.

Allelopathy:

Stubble can be allelopathic.

Population Dynamics and Dispersal:

Spread by seed.

Origin and History:

Europe and Mediterranean.

Distribution:

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

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Temperate.

Soil:

Loamy and clay loam red earths. Less common on sands, grey silts and heavy clays.

Plant Associations:

Capeweed, Annual Ryegrass.

Significance:

Beneficial:

It is the most important legume in temperate Australian pastures.
Fixes nitrogen.

Detrimental:

Weed of crops causing yield reductions due to competition. Weed of lawns roadsides and disturbed areas.

Toxicity:

May cause photo sensitisation in cattle and clover disease in sheep.
Occasionally causes bloat.

Symptoms:

Clover Disease
Reduced fertility, difficult lambing, prolapse in ewes. Lactation and urinary obstructions in wethers.

Treatment:

Avoid continual grazing of areas with high proportions of oestrogenic clovers.

Legislation:

None.

Management and Control:

Thresholds:

10-20/m2 can cause 10% yield loss in cereals.
Dicamba and sulfonylurea herbicides provide good control.

Eradication strategies:

Prevent seed set for 5 years.
Exclude stock to prevent dispersal of seed and burrs.
Hand pull isolated 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 seedlings.
In bushland, 200 g/ha Lontrel®750 or 50 g/ha Logran® applied in early winter provides reasonably selective control. Use 25 mL wetting agent plus 4 g Lontrel®750 or 1 g Logran® or 0.1 g metsulfuron(600g/L) or 0.1 g chlorsulfuron(750g/kg) in 10 L water for hand spraying when they are actively growing. Repeat annually for several years. Plant tall growing perennial species to reduce re-invasion.
Clovers are relatively tolerant to glyphosate, grazing and mowing.

Herbicide resistance:

None reported.

Related plants:

Alsike Clover (Trifolium hybridum)
Arrowleaf Clover (Trifolium vesiculosum)
Balansa Clover (Trifolium balansae)
Berseem Clover (Trifolium alexandrinum)
Birdsfoot Trefoil (Trifolium ornithopodioides)
Bladder Clover (Trifolium spumosum)
Caucasian Clover (Trifolium ambiguum)
Cluster Clover, Ball Clover (Trifolium glomeratum) is a ground-hugging plant with broad leaflets, 5-22 mm long, and globular heads of pink flowers.
Crimson Clover (Trifolium incarnatum)
Cupped Clover (Trifolium cherleri)
Drooping flowered Clover (Trifolium cernuum)
Gland Clover (Trifolium glanduliferum)
Globe Clover (Trifolium globosum)
Hop Clover (Trifolium campestre) is a sprawling plant with fairly broad leaflets, 4-15 mm long, and globular to ovoid heads of yellow flowers. The standard petal is not furrowed and it has 20-50 flowers in the head.
Hare's Foot Clover (Trifolium arvense) is an erect or sprawling plant with narrow leaflets 5-20 mm long and ovoid to shortly cylindric heads of pink flowers.
Kenya White Clover (Trifolium semipilosum)
Knotted Clover (Trifolium striatum)
Lappa Clover (Trifolium lappaceum)
Ligurian Clover (Trifolium ligusticum)
Narrow-leaved Clover (Trifolium angustifolium) is an erect plant with long narrow leaflets, 15-75 mm long, and cylindric heads of pink flowers.
Purple Clover (Trifolium purpureum)
Red Clover (Trifolium pratense)
Rose Clover (Trifolium hirtum) is a hairy plant with fairly broad leaflets, 10-25 mm long, and globular to semi-globular heads of pink to purple flowers.
Rough Clover (Trifolium scabrum)
Sea Clover (Trifolium squamosum)
Shaftal Clover (Trifolium resupinatum)
Slender Suckling Clover (Trifolium micranthum)
Star Clover (Trifolium stellatum)
Strawberry Clover (Trifolium fragiferum)
Subterranean Clover (Trifolium subterraneum) is a ground-hugging plant with broad leaflets, 6-22 mm long, and few-flowered heads of white flowers that form globular buried burrs.
Suckling Clover (Trifolium dubium) is a ground-hugging plant with loose globular heads of yellow flowers and fairly broad leaflets, 4-12 mm long and the end leaflet has a short stalk. and loose globular heads of yellow flowers.
Suffocated Clover (Trifolium suffocatum)
White Clover (Trifolium repens) is a ground-hugging plant with broad leaflets, 4-12 mm long, which often have a pale v-shaped band and globular heads of white flowers.
Woolly Clover (Trifolium tomentosum) is a sprawling plant with broad leaflets, 4-13 mm long and globular heads of pink flowers which become woolly with age.
Zigzag Clover (Trifolium medium)
Trifolium strictum

Plants of similar appearance:

Medics, Trefoils, Soursob, Large flowered Wood Sorrel or Four-o'clock, Oxalis species.

References:

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P453. Diagram.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P221.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P427. Photo.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P491-492.

Gardner, G.A. and Bennetts, H.W. (1956). The toxic plants of Western Australia. (West Australian Newspapers Ltd, Perth). P104-106, Diagram.

Gilbey, D. (1989). Identification of weeds in cereal and legume crops. Bulletin 4107. (Western Australian Department of Agriculture , Perth). P20-21. Photos.

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). P160-162. Photo.

Hyde-Wyatt, B.H. and Morris, D.I. (1975). Tasmanian weed handbook. (Tasmanian Department of Agriculture, Hobart, Tasmania). P102-103. 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). #1228.33.

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). P307.

McBarron, E.J. (1983). Poisonous plants. (Inkata Press, Melbourne). P46. Diagram.

Wilding, J.L. et al. (1987). Crop weeds. (Inkata Press, Melbourne). P110. Diagrams. Photos.

Acknowledgments:

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