Senna cardiosperma is a species of flowering plant in the family Fabaceae and is endemic to the western half of Australia. It is an erect shrub or small tree with pinnate leaves, the number and shape of the leaflets depending on subspecies, yellow flowers with ten fertile stamens in each flower, and flat pods.
Description Senna cardiosperma is an erect shrub or small tree that typically grows to a height of up to . Its leaves are pinnate, the size of the leaves and the number and shape of the leaflets varying with subspecies. The flowers are yellow and borne in upper leaf axils, with ten fertile stamens in each flower, the filaments of different length between long. The fruit is a flattened pod.
Subspecies cardiosperma Subspecies cardiosperma is an erect shrub up to high and has pinnate leaves long on a cylindrical petiole about long, with two to four pairs of linear to narrowly spoon-shaped leaflets long and wide. There is a single sessile gland between the lowest pair of leaflets, and a stipule at the base of the leaf, but that falls off as the leaf opens. The flowers are yellow and arranged in upper leaf axils in pairs or groups of up to four on a peduncle long, each flower on a pedicel long. The petals are long and there are ten fertile stamens, the filaments long. Flowering occurs in winter and spring, and the fruit is a flattened, straight pod long.
Subspecies gawlerensis Subspecies cardiosperma is an erect shrub or small tree up to high and has pinnate leaves long on a cylindrical petiole about long, with five to ten pairs of egg-shaped leaflets with the narrower end towards the base, long and wide. There is a single sessile gland between the lowest pair of leaflets, and a stipule at the base of the leaf, but that falls usually off as the leaf opens. The flowers are yellow and arranged in upper leaf axils in groups of three to six on a peduncle long, each flower on a pedicel long. The petals are about long and there are ten fertile stamens, the filaments about long. Flowering occurs in most months, and the fruit is a flattened, straight or curved pod long.
Subspecies microphylla Subspecies microphylla is an erect shrub up to high and has densely woolly-hairy stems and leaves. The leaves are pinnate, long on a cylindrical petiole about long, with eight to ten pairs of needle-shaped leaflets long and about in diameter. There is a stipule at the base of the leaf, but that falls off as the leaf opens. The flowers are yellow and arranged in upper leaf axils in pairs or groups of two to four on a peduncle long, each flower on a pedicel long. The petals are long and there are ten fertile stamens, the filaments about long. Flowering occurs in spring, and the fruit is a flattened, straight pod long.
Taxonomy This species was first formally described in 1876 by Ferdinand von Mueller who gave it the name Cassia cardiosperma in his Fragmenta Phytographiae Australiae from specimens collected by Jess Young. In 1989, Barbara Rae Randell transferred the species to Senna as Senna cardiosperma in the Journal of the Adelaide Botanic Garden. The specific epithet (cardiosperma) means "heart-seeded".
In the same edition of the Journal of the Adelaide Botanic Gardens, Randell described three subspecies of S. cardiosperma, and the names are accepted by the Australian Plant Census: Senna cardiosperma (F.Muell.) Randell subsp. cardiosperma Senna cardiosperma subsp. gawlerensis Randell Senna cardiosperma subsp. microphylla Randell
Distribution and habitat Subspecies cardiosperma grows on rocky hillsides in arid places in the Coolgardie, Great Victoria Desert, Mallee, Murchison and Nullarbor bioregions of Western Australia. Subspecies gawlerensis grows in rocky places and in sand on the Eyre Peninsula and in the northwest corner of South Australia, and subsp. microphylla grows in arid shrubland in the far north-western corner of South Australia and in the south of the Northern Territory.
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