Real World Gardener Rock Isotoma in Plant of the Week

November 16th, 2019


Rock Isotoma: Isotoma axillaris

Family: Lobeliaceae

Fancy a shrubby ground cover plant with purple starry flowers that’s a real standout?

Of course, we all want those in our garden because they fit into any bare spot.

Let’s find out why we should grow it.


Isotoma axillaris

I'm talking with Adrian O’Malley, horticulturist and native plant expert.

Rock isotoma is a flowering perennial that grow up to 40cm high x 40cm wide.

Upright stems are often a purplish colour and covered with short, soft hairs quickly becoming smooth.

The leaves are about 1.5–15 cm long and 0.5–5 mm wide with deep, toothed, linear lobes sharply pointed at the apex.

Rock Isotoma grows naturally in sandstone rock crevices in bushland, but don’t let that stop you from growing it in your garden.

Treat it as a biennial plant, but as it self seeds that’s not really a problem.

You may see if for sale in your local nursery Isotoma ‘Blue Star’

It’s a terrific plant with multibranched stems, that grows into a great mound of lilac-coloured, star-like flowers

If you have any questions either for me or Adrian, why not write in to

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