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A shrub to 40 cm high, with densely hairy stems.
It has an interesting natural distribution, with several disjunct occurrences across NSW, growing as far north-west as the Warrumbungles National Park, then occurring far to the south-east in the Putty area (north-west of Sydney), then with scattered records through the Blue Mountains, and with a cluster of disjunct records around Nowra.
It is found in heath and dry sclerophyll woodland and forest on sandstone and sandy substrates.
In Tetratheca spp., leaves are simple and can be arranged alternately or in opposite pairs or whorls. Some species can exhibit varying leaf arrangements (dimorphic). In this species, leaves are alternate to rarely-opposite, linear to elliptic, to 15 mm long, to 1.5 mm wide, hairless or with glandular hairs.
Tetratheca spp. tend to produce solitary or paired flowers in leaf axils, extending well beyond the foliage. They typically have 4 petals which resemble an even cross (some flowers can have 5 petals), with 8 stamens and 1 carpel. Flowers often point downwards (pendent) which attracts certain insects. In this species, flowers are deep lilac-pink, to 30 mm in diameter, flowering: spring-summer.
Tetratheca spp. produce fruit as capsules which open longitudinally. In this species, the fruits is to 5 mm long with seeds to 4 mm long, brown and smooth, with fine hairs and an appendage.
This species is not known to be readily cultivated and no information is available at the time of this publication. It may be more readily cultivated in the future. It grows naturally on sandstone and sandy substrates and so may need similar soil conditions to thrive. Check with local native nurseries for availability.
Some Tetratheca spp. are cultivated commonly, especially T. thymifolia and they make very attractive additions to gardens.
Plant them along open borders or in rockeries for best affect, with well-drained soils and some shade during the warmer months.
Propagation can be carried out from seed but this is rarely available.
Cuttings of hardened, current season’s growth usually strike fairly-readily. Cuttings of young suckering shoots will also work well provided the propagation mix is well-drained. The use of a root-promoting hormone is advised for greater success. Cuttings are best done from November to April.
Tetratheca comprises around 50 to 60 species, endemic to Australia. They occur in all states with the exception of the Northern Territory. NSW currently has 16 species.
The flower colours have given rise to the common name for many species of “Black-eyed Susan”. However, note that this common name applies to several exotic species.
Most Tetratheca spp. would die in a fire and regenerate from the seed bank.
Tetratheca – Ancient Greek – tetra meaning “four”, and theke meaning “sac or box”, relating to the condition of the stamens in the flowers which have four lobes or cells.
decora – Latin meaning “decorative”.
This species is not considered to be at risk of extinction in the wild.
NSW Flora online (PlantNET) Tetratheca decora profile page: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Tetratheca~decora
Wikipedia – Tetratheca profile page: https://en.wikipedia.org/wiki/Tetratheca
The Family Tremandraceae – APS NSW https://austplants.com.au/resources/Documents/South-East-Documents/Articles_About_Plants_and_Gardens/The_Family_Tremandraceae_John_Knight.pdf