I photographed this one last week in the Palmtree area (near Ravensbourne), where it grew on red soil. You can see it on the 4k walking track with follows the old MunroTramway, which begins in Palmtree road. A blue signpost at the beginning tells us that the track has been developed by the local council as one of our “Great Short Walks".
This native indigo is a slender shrub, pretty year-round with its blue-green leaves, but tending to go unnoticed in the wild until it produces these lovely flowers.
The species is widespread throughout much of Australia, and very variable in form, but our local form is a small shrub, usually less than a metre high.
It can be used effectively in a garden, especially if planted in a postition where advantage can be taken of the contrast between its unusual leaf colour, and green-leafed plants.
Tip pruning regularly is important, to help it grow into a more dense shrub.
This is a frost hardy plant, preferring well-drained soil and semi-shade.
Austral indigo is related to the plants which have been used to produce an indigo dye, since time immemorial. (The "woad" used by ancient Britons to tattoo and dye their skins was indigo, and so is the dye in blue jeans.) Austral indigo contains less of the active ingredient than the species that are used commercially, but Australian dyers have used it to produce green, yellow, a good fast red, and of course the traditional blue.
Here are some sites of successful modern hobby dyers who have used it:
The last has a photo of an interesting, multi-coloured piece of knitting, made by treating the Indigofera australia leaves in different ways to create dyes of different colours.
IF YOU WANT TO USE Austral Indigo FOR DYING, PLEASE GROW YOUR OWN PLANTS. Nature is doing it tough, and leaf-collecting in the quantities needed for even a small amount of dye may deprive native insects of the food they need to make the next generation, and may even kill the plants.
Seed of the species can be bought on the internet. This would be of plants from other parts of Australia. If you care about cross-pollination damaging the integrity of our local plants (the same problem that CAUSES many people to strongly oppose GM crops), then you will collect local native seed when it becomes available in November. (Once again, correct behaviour is to collect no more than about 10% of the seed you see around you. Nature needs its seeds, too.)
It is easy to grow if you use the boiling water method: Put the seeds in a coffee cup. Pour boiling water on them. Leave to soak overnight. Plant the seeds that have swelled, in the morning. Repeat the process for any seeds that didn't swell. (They have a tiny hole through the outer coat that is blocked with wax, and the wax must be melted for the water to penetrate to the seed inside and start it growing.)