Southern Star (Oxypetalum coeruleum)

Southern Star (Oxypetalum coeruleum), a striking South American milkweed adopted into Victorian horticulture for its sky blue flowers.

Indigenous to Uruguay and SE Brazil, the plant still carries the informal honorific Tweedia for John Tweedie, a Scottish gardener who was among the first British collectors to access South America following the revolutions that threw off Spanish rule, sending seeds and specimens to collections across the UK. Hooker and Arnott named the genus in 1834, and Scottish botanist David Don described this species in 1836, noting it ‘will soon become a common ornament of the flower-garden.’ Although the genus Tweedia endures, this species was revised into Oxypetalum by South American botanists in 1989.

Advertised for sale at Sydney by 1848, later reports noted its use in the Royal Society Gardens at Hobart (1860), and in the Melbourne Botanic Gardens (1880). A fashionable cut flower, the species has never been common in Australian gardens, but found regular favour among columnists for its drought-hardiness and blue colour. While singing praises, writers also acknowledged the plant ‘grows freely from seed which is produced by plants growing about Sydney’ (1890) and ‘is sure to look after itself once you introduce it to your garden, for seed is produced in abundance, and this is carried by the wind into strange places’ (1906).

Southern Star is today well-established in NSW, particularly along the Great Dividing Range, where it can also be found in SE QLD and the ACT; there are further reports of small populations established in NZ and South Africa. Frost sensitive, Southern Star appears most successful in dry, thin soils on rises where rock exposures provide a degree of shelter and break up the dominant grass layer.

In Victoria, the species is so far known only from the north side of Sunbury, where since the 1990s a small number of plants have been found growing on local basalt rises. This tiny population is notable for having endured several decades despite a degree of ongoing management in the native grasslands it is haunting.