Hibiscus trionum L.
Hibiscus is the Greco-Latin name for a Mallow.
Trionum is Latin meaning 3 coloured.
Bladder Ketmia because it has bladdery fruits.
Other Names:Bladder Hibiscus (New Zealand)
Flower-of-an-hour because the flowers only last an hour or two.
Venice Mallow (USA)
Summary:A lobed leaved, annual (or biennial) to 1 metre tall with deeply divided leaves that have 3-5 lobes (that may be toothed) and star type and simple hairs. The pale yellow, 5-petalled flowers with purple centres occur from January to March and form bladdery fruits.
Two. Triangular, thick. Hypocotyl stout with simple hairs that point towards the base. Indistinct veins radiating from the base on both surfaces. Tip round. Edges smooth to indented. Base indented. Surface smooth. Petiole longer than the blade and covered in glandular and non glandular hairs.
First leaves:Alternate, dull green, slightly thickened. Oval to round with obvious, light, forked veins. Tip round to flat or pointed. Edges lobed and undulating. Base indented. Lower surface densely covered with simple and star type hairs. Upper surface sparsely covered with simple hairs. Petiole about the same length to shorter than blade with simple and star type hairs from warty bases.
Stipules - Parallel sided and hairy on later leaves
Petiole - 5-20 mm long. Shorter than blade.
Blade - Shiny, dark green, oval, 20-75 mm long x 25-45 mm wide, deeply divided into 3-5 lobes that are also lobed or toothed. Tip round. Edges lobed and often red. Base squarish. Sparse star type and simple hairs especially on the lower surface. May be almost hairless on the upper surface.
Lower leaves may be almost round in some varieties.
Stems:Erect, to somewhat sprawling, 300-1500 mm tall, freely branched at the base. Sparse star type and longer simple hairs and vertical rows of fine, appressed hairs. Moderately hairy when young and usually sparsely hairy at maturity.
Flower head:Flowers in racemes at the ends of stems or single flowers in axils on short stalks about 10 mm long. 7-12, linear, free, hairy bracts, 10 mm long under flower.
Flowers:Short lived (1-2 hours), pale orange-yellow with purple centres.
Ovary - 5 celled.
Style - Branches free.
Stigma - head like.
Calyx - 5, united, membranous, bladder like, 10-15 mm long and enlarging to 23 mm long at the fruiting stage with more than 20 hairy prominent green or purple, raised veins. Star type hairs. Tube broad, bell shaped. Lobes egg shaped, with an indented base and pointed tip.
Petals - 5, Pale orange-yellow with a purple (dark brown, red or orange occasionally) spot at the base, 20-40 mm long.
Stamens - Many.
Anthers - Yellow, many.
Fruit:Globular, 5 celled capsule, 10-15 mm diameter and enclosed in the enlarged papery or bladder like calyx. Splits open along its back side when ripe (loculicidal) to release many seeds. Hairy.
Seeds:Red-brown to black, angular to kidney shaped, 2-2.5 mm long x 2-2.5 mm wide by 1.5 mm thick. Tip round. Edges concave and convex. Base rounded with stalk remnant. Surface finely granular with warts, ridged and dull. Hairless.
Key Characters:Annual softly wooded herb, less than 1.5 m high.
Leaves cut to the base into 3-5 oblong lobes.
Involucre (or epicalyx) of 7-12 free linear bracteoles.
Calyx shortly lobed, bladdery, glabrous to sparsely hairy, pale with dark veins and ovate cordate lobes.
Ovary - 5 celled.
Styles separated towards the apex
Style branches free, filiform and terminating in a capitate stigma.
Fruit a loculicidal, dehiscent capsule.
Flowers short lived, pale orange-yellow with purple centres.
Adapted from John Black and Judy Wheeler.
Annual or biennial. Grows in the warmer months.
Flowering times:Summer in SA.
January to March in WA.
October to March in NZ.
Seed Biology and Germination:Buried at 0-2 cm deep, 71% seed survives 1 year and 17% survives 4 years.
Buried at 10 cm deep, 72% seed survives 1 year and 37% survives 4 years (S. Walker, GRDC 2009).
Variety vesicarius has the lower leaves without lobes and is a native of northern Australia.
Allelopathy:Population Dynamics and Dispersal:
Free seeding and spread by seed. Often occurs as single plants but can form dense stands. Most common in summer following rains or flooding.
Origin and History:Eastern Europe. Cosmopolitan.
Distribution:NSW, NT, QLD, SA, TAS, VIC, WA.
Courtesy Australia's Virtual Herbarium.
Temperate to sub tropical.
Soil:Common on grey clay soils of flood plains and less so on red earths.
Used medicinally by southern African natives as a cure for Roundworm.
Fodder of rather poor value.
Detrimental:Weed of crops, cultivated fallows, roadsides and disturbed areas.
Weed of degraded pastures.
Toxicity:Possibly toxic. Contains malvalic acid that affects the quality of eggs.
Management and Control:Cultivation normally keeps it under control.
In pastures, the introduction of more vigorous species and better fertiliser and grazing management usually provides sufficient control. If necessary in legume based pastures, spray with 500 mL Spinnaker® when the Bladder Ketmia has 3-6 leaves and graze heavily 7 days later.
Cultivate or spray the area with 1 L/ha oxyfluorfen to control existing plants and repeat as necessary or apply 4 L/ha oxyfluorfen to provide residual control of seedlings. Repeat annually until no more seedlings appear.
Start control programs at the top of flood ways to reduce re infestation.
Carfentrazone (Affinity® or Hammer®) is also expected to give good control.
Herbicide resistance:None reported.
Related plants:Chinese Hibiscus (Hibiscus rosa-sinensis) is the ornamental with large, bright red flowers and a long, protruding style.
Rosella (Hibiscus sabdariffa) is found in more topical areas.
Hibiscus diversifolius is more prickly, tends to grow near the coast and has the flowers along the stalk (in racemes).
Cotton (Gossypium hirsutum)
Plants of similar appearance:Gooseberry
References:Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P184. Photo.
Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P565. Diagram.
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). P481. Photo.
Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).
Gardner, G.A. and Bennetts, H.W. (1956). The toxic plants of Western Australia. (West Australian Newspapers Ltd, Perth). P140.
Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume . P. Diagram.
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). P174. Photo.
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). #500.2.
Marchant et al (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P144.
Moerkerk, M.R. and Barnett, A.G. (1998). More Crop Weeds. R.G. and F.J. Richardson, Melbourne. P105. Diagrams. Photos.
Roy, B., Popay, I., Champion, P., James, T. and Rahman, A. (1998). An Illustrated Guide to Common Weeds of New Zealand. (New Zealand Plant Protection Society). P186. Photo.
Stucky, J.M. (1981). Identifying Seedling and Mature Weeds Common in the Southeastern United States. (The North Carolina Agricultural Research Service and The North Carolina Agricultural Extension Service, North Carolina State University, Raleigh). P70-71. Photo. Diagrams.
Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.