Isotoma axillaris

Rock Isotome, Showy Isotome, Blue Stars

Family: Campanulaceae

Isotoma axillaris is widespread from Victoria through New South Wales and southern Queensland. It grows naturally in damp crevices or shallow soil in rocky areas.

I always have a few Isotoma axillaris growing in my garden as they are a great small plant, growing to about 40 cm high and about that wide, with a prolific display of blue star flowers that are about 3 cm in diameter.

The flowering period is quite long, starting in October, and they flower well into late summer if not allowed to dry out for too long.

In the garden

I use them to define borders and they look great growing next to the blue flowering Brachyscome multifida.

They prefer to grow in full sun in lighter soils but I have found them quite adaptable in my northern Sydney garden. Isotoma axillaris grow much better if not allowed to dry out for too long and after a wet 2011 winter, they are growing and flowering the best for years in my garden.

Maintenance: After flowering the foliage will die off and I then cut the plant back hard, to encourage fresh new growth. Every two or three years Isotoma axillaris are eaten by little green caterpillars, 2 or 3 cm long, the exact same colour as the foliage, which can be removed easily by hand (once you know what to look for).

A word of warning: Be careful when cuttings stems as they exude white sap that produces a severe stinging sensation if rubbed on eyes and may cause irritation to sensitive skin. However, this should not stop you growing these plants as the flowering display is worth the care.


If conditions are good you will have just enough seedlings that can be dug up and replanted where you require them.

Other information

Isotoma: from iso, meaning equal, and toma, meaning a section, referring to the equal lengths of the corolla segments. axillaris: borne in the axil, referring to the position of the flowers in the axils of leaves.

By Jeff Howes