Poison Pratia

Pratia concolor (R.Br.) Druce

Synonyms - Lobelia concolor, Pratia erecta.

Family: Campanulaceae

Names:

Pratia named after Charles L. Prat-Bernon a sailor who died on Freycinet's voyage in 1817.
Concolor

Other Names:

Milkweed
Milky Lobelia
White-root

Summary:

A hairless, rhizomatous, semi succulent, perennial vine that roots at the nodes and has oval scalloped leaves and small white or pink flowers. There are separate male and female plants. Plants exude white sap when damaged and often form mats.

Description:

Cotyledons:

Two.

First leaves:

Leaves:

Alternate. Exude milky sap when damaged.
Stipules - None.
Petiole - Very short to none.
Blade - Oval to spear shaped, 10-30 mm long x 3-15 mm wide, firm, spreading horizontally in one plane, broad at the base. Tip rounded to pointed. Finely toothed or scalloped edges. Base squarish to indented and a lighter colour. Hairless

Stems:

Whitish, low lying to bent up at the ends, Often zigzagging. rooting at the nodes. Exude milky sap when damaged. Hairless.

Flower head:

Single flowers on axillary stalks that are usually shorter than the floral leaves and near the ends of branches.

Flowers:

White or pink, 6-10 mm long on 3-13 mm long stalks that are curved in fruit.
Dioecious (separate male and female plants)
Ovary - 2 celled, inferior, 2-5 mm long.
Stigma - 2 lobed.
Sepals - Bell shaped, 2 mm long with 5 spreading lobes 2.5-4 mm long.
Petals - White or pink and often violet streaked, 6-9 mm long. Tubular with the tube split to the base, 5 short, spreading, oval lobes that are turned to one side. Hairy inside.
Stamens - attached at the base of the corolla tube.
Filaments - free for about half their length.
Anthers - On male flowers, blue black with two lower ones tipped with bristles, 3 upper anthers slightly longer and curved down onto the 2 lower ones. Pale sterile anthers on female flowers.

Fruit:

Globular, fleshy, 4-8 mm diameter, not splitting when ripe, crowned by the persistent calyx. Hairless.

Seeds:

Cream, globular, less than 1 mm diameter. Minutely roughened surface.

Roots:

White, fleshy roots, exude milky sap when damaged. Rhizomes. Stems root at the nodes.

Key Characters:

A hairless, rhizomatous, perennial vine.
Leaves, stems and roots exude a white milky sap when damaged.
Prostrate herb, stems rooting at the nodes.
Leaves rather broad with a broad base, ovate to lanceolate to oblong-lanceolate, 10-30 mm long, glabrous, toothed, green on lower surface, sessile or almost so.
Peduncles 3-13 mm long, shorter or scarcely longer than the leaves.
White or pink, tubular, 5 lobed flowers.
Flowers resupinate
Calyx lobes without basal teeth.
Corolla White or pink, > 5 mm long, tube split open to the base, the limb 2 lipped. petals about the same size.
Ovary 2 celled.
Stamens attached at the base of the corolla tube.
Anthers cohering in a ring round the style.
Fruit more or less succulent, indehiscent.
Adapted from John Black, Gwen Harden and John Moore.

Biology:

Life cycle:

Perennial.

Physiology:

Reproduction:

Flowering times:

Summer in Western NSW.
Mainly January to April in NSW.

Seed Biology and Germination:

Vegetative Propagules:

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Spread by seed and creeping rhizomes.

Origin and History:

Australian native

Distribution:

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

Courtesy Australia's Virtual Herbarium.

Habitats:

Often near water.
Grows in wet and irrigated areas.

Climate:

Temperate

Soil:

Clay and loamy soils of flood plains that are usually poorly drained.

Plant Associations:

Significance:

Beneficial:

Fodder but may be toxic. Not very palatable.

Detrimental:

Weed of crops, pastures, irrigated pastures, drains, waterways, swamps and other moist areas.

Toxicity:

Toxic to horses probably causing Murrami disease. Contains alkaloids.
Rarely eaten so field cases are uncommon.

Symptoms:

Sudden collapse or death of horse after mild exercise or fright.

Treatment:

Remove stock from infested areas.
Don't graze infested areas if adequate alternative feed is not available.

Legislation:

None.

Management and Control:

Thresholds:

Eradication strategies:

Try a mix of 100 mL glyphosate(450g/L) plus 1 g metsulfuron(600 g/kg) plus 25 mL Pulse® in 10 L water and spray until just wet when the plants are actively growing.

Herbicide resistance:

None reported.

Biological Control:

Related plants:

White-root (Pratia purpurascens) medicinal herb containing lobeline.
Pratia darlingensis
Pratia clematidea has a strong smell and purple blue flowers.
Pratia pedunculata

Plants of similar appearance:

Creeping Knotweed has tiny flowers and a membrane (ochrea) at the base of the petiole.
Bindweed has a membrane (ochrea) at the base of the petiole.
Sorrel has arrow shaped leaves and a membrane (ochrea) at the base of the petiole.

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P183. Photo.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P813.

Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P630. Photo.

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

Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume 3. P128. Diagram.

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). #816.1.

Moerkerk, M.R. and Barnett, A.G. (1998). More Crop Weeds. R.G. and F.J. Richardson, Melbourne. P74. Diagrams. Photos.

Acknowledgments:

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