Soliva sessilis Ruiz & Pav.
Synonyms - Soliva pterosperma, Gymnostyles pterosperma.
Soliva commemorates Dr Salvador Soliva of Spain.
Sessilis is Latin for sessile and probably refers to the sessile flower heads.
Pterosperma is from the Greek pteron meaning wing and sperma meaning seed and refers to the winged seed.
Summary:A light green, low lying annual to short lived perennial plant with stoloniferous stems and much divided, carrot like leaves up to 10 cm long, in a dense rosette with sharp, prickly seeds formed in spring where the stems branch. It is common in lawns.
Leaves:Alternate. Forms dense rosettes of leaves, often clustered under the flower heads. Additional rosettes formed where stolons take root.
Petiole - Short, often purplish red on lower leaves. Broad papery base that clasps the stem.
Blade - Much divided into narrow segments, 15-50 mm long x 12 mm wide overall. Long soft, silky hairs.
Stem leaves - similar but petiole base is narrower.
Stems: Mat forming, branching stolons to 100 mm long, forming rosettes of leaves at the nodes where they root. Long soft, silky hairs. Sometimes stemless.
Flower head:Green, single, 3-10 mm wide, at the centres of rosettes or scattered singly along stems in leaf axils (never clustered near the base), slightly convex (not globular) with bracts in 2 rows around the outside (involucre). No stalk. Forms 'burrs' with short very sharp spines.
Flowers: Edge florets female. Central florets male, tubular, 4 lobed, sterile.
Bracts - Egg shaped to oval with a pointed tip, hairy and thin.
Florets - Ray florets in several rows, female, no corolla.
Disk florets sterile or abortive, tubular, 4 lobed, fewer and smaller than the ray florets.
Ovary - Receptacle narrow, small, conical.
'Petals' - none.
Fruit:Wedge shaped to oval, greenish achene, 3 mm long x 2.5-4 mm wide (including wings), flattened, curved. Rigid spine at top as long as the body. Body has rough hairs. Broad thin, incurved, 2 lobed wings, that are widest near the middle, narrowed below and flared at the base, near the tip they form 2 very sharp, slender spines about 1 mm long. Hairy on the convex face at the bases of spines. No pappus. Style hardened, persistent as long as the body of the achene.
Seeds:Enclosed in the achene.
Roots:Fibrous. Stoloniferous stems root at the nodes.
Key Characters:Small herb.
No milky latex.
Heads sessile, heterogamous-discoid, distinct, female flowers in several to many rows with no ligule, disk flowers few, 4 toothed.
No corolla on female flowers.
Involucre bracts pubescent, herbaceous or thin in 2 sub equal rows, not spine tipped.
Achenes flattened, winged with a persistent hardened style, no pappus.
Adapted from J.M. Black and N.S. Lander.
Annual or short lived perennial. Seed germinates from winter to early spring and forms a rosette of leaves. Stems emerge from the rosettes and form new rosettes where they root at the nodes. In spring flower heads form. From late spring to summer the seeds ripen and harden as burrs with many sharp spined prickles.
By seed and stolons.
Flowering times:Spring to summer in western NSW.
October to November in SA.
September to November in Perth.
Spring in WA.
Seed Biology and Germination:Vegetative Propagules:
Stolons that root at the nodes and form new rosettes.
Population Dynamics and Dispersal:
Spread mainly by seed. Growth of stolons that root at the nodes and form new rosettes rapidly increases the density of new infestations.
Origin and History:South America. Chile.
Distribution:ACT, NSW, QLD, SA, VIC, WA.
Courtesy Australia's Virtual Herbarium.
Habitats:Moist open areas.
Soil:Sands, red brown earths and many other soil types.
Plant Associations:Turf, lawn and many others.
Weed of lawns with very sharp spined seed. Weed of playing fields, roadsides, vegetables, recreational areas, pastures and disturbed areas.
Toxicity:Not recorded as toxic.
Legislation:Noxious weed of WA.
Pest plant of the Melville shire in WA.
Management and Control:Hormone herbicides provide good control if applied in winter before flowering. Bromoxynil provides good control up to seed set.
Spray with bromoxynil plus MCPA in August and November each year.
Small areas can be treated with 1 litre of Tordon® 75-D in 250 litres of water in June to provide residual control for the season.
Herbicide resistance:Biological Control:
Dwarf Jo-jo (Soliva anthemifolia) has softer spines and rarely forms stolons.
Soliva stolonifera has globular flower heads and occurs in NSW and VIC.
Plants of similar appearance:Dwarf Jo-jo and Carrot weed. Carrot weed has flower heads on stalks.
References:Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P116. Photo.
Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P881.
Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P370, 373. Diagram.
Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P669. Photo.
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). P104. Photo.
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). #1144.2.
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). P707.
Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P308-309. Photos.
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