An open erect to spreading shrub, growing to 3 metres tall by up to 2 metres wide, sometimes multi-stemmed.
It is a very widespread species. It grows over most of NSW, into the far inland and it is thought there are different forms. It extends up the Queensland coast and tablelands, the south and east of Victoria, South Australia and the west of Western Australia with disjunctions in-between.
It often grows in dry sclerophyll woodlands and forests. It can be seen on roadsides, usually in low numbers, across NSW. It tends to be found on heavier soils but can be found on sandy soils as well.
Indigofera australis is a member of the “pea” family.
This generally means that leaves are alternate with stipules at the base of the petioles. In this species, leaves are compound (another common feature in many genera), arranged alternately, with leaves consisting of separate leaflets, terminating in an individual leaflet, called an imparipinnate compound leaf. Leaves are to up to 10 cm long by 8 cm wide, with up to 25 leaflets, each up to 4 cm long and 1 cm wide.
Flowers are, of course, pea-shaped (a term sometimes used is papilionate), with 5 petals in a fixed arrangement; the main back petal is called the “standard”, two lateral petals called “wings” and two fused petals at the bottom called the “keel” (in which the anthers and one carpel tend to be hidden).
In this species, flowers are produced in racemes up to 15 cm long by about 3 cm wide. Flowers are pink to purple-pink.
The fruit of all peas is a pod. In this species, they are linear and terete, up to 5 cm long, ripening to brown and then splitting open to release black seeds.
Indigofera australis is a plant referred to by many online sites and gardening books as “underutilised”. It definitely should be grown more often as Indigofera australis has very attractive flowers and beautiful coloured foliage.
I planted some of these plants about 10 years ago in my garden in the northern Sydney suburb of Westleigh and they have all grown to about 2 metres high and about 1.8 metres wide.
The plant has attractive pink to purplish flowers that appear in late August and flower into October. The flowers contrast well against the pinnate blue green leaves.
Reference books advise that they tolerate moderately heavy frosts, however my seed grown plants did not survive the first frost in my daughter’s Southern Highlands garden. Perhaps I did not give them enough time to acclimatise to the colder growing conditions.
Maintenance: I have found that Indigofera australis is at its best if pruned from early age to encourage a denser shape. If left to their natural growth, they tend to be a much more open plant. I prune them quite hard, after flowering and try to avoid pruning into very old wood, as I have found there will be no new regrowth.
Overall, Indigofera australis is a stunning plant in and out of flower, often available in nurseries and at least one should be in every semi-shaded garden.
Propagate from seeds, which should be pre-treated in boiling water.
One subspecies, subspecies australis, is currently recognised in NSW.
This species will regenerate from fire from seed, sometimes in large numbers.
Indigofera is a very large genus of over 700 species, occurring in tropical and subtropical and temperate regions in bot hemispheres. There are about 50 species in Australia, most of which are endemic. Some species are naturalised. NSW currently has 18 species – 3 of which are exotic.
Indigofera – Neo-Latin for “bearing Indigo”. Indigo is a purple dye originally obtained from some Indigofera species.
australis – Latin – meaning “southern”, referring to the geographical distribution of the species.
This species is not considered to be at risk of extinction in the wild.
NSW Flora Online (PlantNET) – Indigofera australis profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Indigofera~australis
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.
Gardening with Angus – Indigofera australis profile page https://www.gardeningwithangus.com.au/indigofera-australis-australian-indigo/