The genus Gastrolobium consists of over 100 species*, all but two of which are found only in Western Australia. Recent botanical revision has seen all members of the genus Brachysema transferred to Gastrolobium. They are generally small shrubs ranging from prostrate in habit to about 2 metres. Many species of Gastrolobium are known to be poisonous and some have been associated with stock poisoning. Because of this, few gastrolobiums are cultivated, the exceptions being a number of species previously in Brachysema.
Gastrolobium calycinum is an erect or bushy shrub to 1.5 m high. Leaves are variable and are narrow to broadly lance-shaped to about 50 mm long. The pea-type flowers are yellow with a red or pink centre. Flowering occurs in late spring to early summer.
This species is known to be highly toxic and has been implicated in stock poisoning.
The typical “pea” flowers consist of 4 petals; the “standard”, the “keel” and two “wings”, as shown in the diagram.
As one of the toxic species, G. calycinum is not usually cultivated. It is, however, an attractive shrub and would probably grow well in well drained soils in full sun to semi-shade.
Propagation is easy from seed following pre-treatment to break the physical dormancy provided by the impervious seed coat. Pre-treatment can be carried out by abrasion or by the use of boiling water (further details can be found in under the “Propagation” tab of the “Pea Family” page). The seed retains viability for many years. Cuttings strike well using firm, current season’s growth.
* Chandler G T, Crisp M D, Cayzer L W and Bayer R J (2002), Monograph of Gastrolobium (Fabaceae: Mirbelieae). Australian Systematic Botany 15 (619-739).
Photo: M D Crisp – Australian National Botanic Gardens