Wide-leaf bladder ketmia biology
Hibiscus tridactylites Lindley    (was Hibiscus trionum var. vesicarius)
Family: Malvaceae (Hibiscus family).

Common names: Wide-leaf bladder ketmia, Bladder ketmia, Flower-of-an-hour, Rose mallow, Wild gooseberry.

Confused with: Narrow-leaf bladder ketmia (H. verdcourtii Craven), and Native rosella (Abelmoschus ficulneus) at the seedling stage. The bladder ketmia varieties can be distinguished by:

* Leaf shape - narrow-leaf bladder ketmia leaves are 2 – 9 cm long and deeply divided with the lobes much wider at the middle and towards the end than at the base, where wide-leaf bladder ketmia leaves are 2 – 10 cm long and wide and the lobes are more or less uniformly wide to their base.

* Flower colour - narrow-leaf bladder ketmia flowers have a deep red/purple throat, where wide-leaf bladder ketmia flowers are uniformly creamy/white.

Description:

There are two types of wide-leaf bladder ketmia, most easily differentiated by the colour of the centre of the flower. The yellow centre flower type (pictured) is common throughout New South Wales and Southern Queensland. The red centre flower type (on the cover of WEEDpak) co-occurs with the yellow centre type on the Darling Downs and is found in Central Qld. Both types are similar in growth and lifecycle and in the problems they cause.

Seedling leaves - the cotyledon leaves are similar in shape with one leaf circular to broadly oval in shape and slightly larger, and the other circular with a slightly flattened base, 14 – 22 mm long and wide, and on stems 10 – 20 mm long.

Early leaves - the first true leaf is broadly oval-shaped with shallow rounded teeth along the margins. The second and third true leaves are generally unlobed while the fourth true leaf has three shallow lobes.

Adult leaves – are three to five-lobed, the yellow centre flower type 20 – 105 mm long, 15 – 105 mm wide, borne on 20 – 35 mm long stems, while the red centre flower type 20 - 110 mm long and 15 – 75 mm wide (generally not as wide), borne on 30 mm long stems. The leaves usually have a shiny waxy texture and feel with very shallow and irregular teeth.

Mature plants – are always erect, to 150 cm high and sometimes with coarse hairs on the stem, have some branching and arise from a deep taproot to 100 cm depth. The plant stems are always green.

Flowers – the single hibiscus-like flowers are borne in the upper leaf forks, with five cream to white petals, and either yellow or cream coloured centres, or deep red-maroon centres, depending on type. These flowers are generally around 30 mm wide, borne on stems 5 – 20 mm long and are often longer on plants of the red centre flower type.

Seed heads – the straw- to brown-coloured bladder-like seed heads are covered in rough hairs, have raised ribs, 10 – 20 mm long that split into five valves upon maturity. There are 25 - 40 shiny black kidney shaped seeds that are 3 mm long and 2 mm wide in each seed head.

Lifecycle/Biology: Wide-leaf bladder ketmia seedlings emerge in successive seedling flushes after rainfall or irrigation during the spring - autumn period. Dense flushes to 200 seedlings/m2 have be observed. Rapid growth follows with flowering starting around 40 days after emergence. Flowering occurs from late-spring, and during summer and autumn, with large numbers of flowers observed a week or more after rainfall and irrigation. Flowers open for only part of a day, or at most one day. Mature seed can be set within 50 - 60 days of emergence, with seed production peaking in late summer and early autumn. Up to 8,000 seeds can be produced on medium sized plants and seed can be produced on plants that are less than 5 cm high in late autumn. Wide-leaf bladder ketmia is an annual plant. Plants are very frost sensitive and are killed by frost in autumn and winter. The seed has strong dormancy after being shed with very little fresh seed germinating. Seed has 50% viability after one year of soil burial but only 15% after two years.

Ecology: This plant is a common weed of summer crops, disturbed areas and of wasteland. It is common on heavy clay soils, particularly after flooding and heavy rainfall.

The problem: The plant is a common weed of irrigated and dryland crops and may be an alternative host to some insect and crop pathogens. This variety is more a problem in western and warmer cotton growing areas. While individual plants are not overly competitive, dense stands can cause localised yield losses and early control is important to prevent seed set.

Distribution: Occurs throughout Australia

Origin: Probably a native species.

References:

Crop Weeds of Northern Australia, p. 134 - 135. The description is relevant for both wide-leaf and narrow-leaf varieties. The central Queensland specimen pictured on page 135 is probably the red centre flower type of wide-leaf bladder ketmia.

Johnson, S. B. Ecology and management of bladder ketmia (Hibiscus trionum) and other emerging problem Malvaceae weeds.

Compiled by:
Graham charles and Stephen Johnson