Hangers On

SERIES 35 | Episode 02

Josh heads into the bush to learn more about a fascinating native plant that is truly unusual.

Botanist Ryan Craig is completing a PhD on botanical parasitology – that is, plants that feed off other plants for their nutrients and water.

There are 4,500 plants around the world that do this.

One that Ryan has a special interest in grows locally in the Perth hills, often on a favourite host plant, the native 'egg and bacon' plants, Daviesia angulata.

The parasitic plant is called Pilostyles hamiltoniorum, and while there are 134 species of Daviesia in WA, Pilostyles will only grow on 10 of them.

There are 11 species of Pilostyles in the world, including three in Australia – all endemic to WA. All the species infect shrubs from the pea family.

The Pilostyles looks like tiny buds along the stem of the host plant, but these are actually flowers erupting from the main part of the parasitic plant, which is hidden inside the stem of the plant.

Ryan is keen to learn more about how the two plants interact.

The parasitic plant has no leaves, so it is not photosynthesising, and it has no stem or roots. Yet somehow these plants not only flower but are pollinated by native bees, then form purple berries containing up to 100 tiny seeds – but no-one quite knows how these seeds are distributed, nor how they germinate or find their way into a new host plant.

Weirder still, its closest relatives are the Cucurbit family, which includes cucumbers and pumpkins.

The plants are doing some considerable damage as they force their way through the internal structure of the host's stems, but another mystery is that some host plants don't seem affected by their presence, and others struggle.

Another challenge for science is to work out if there are multiple Pilostyles plants within each host or one single plant.

"There's a lifetime of research that could go into this plant," says Ryan.

Filmed on Whadjuk Country | Pickering Brook, WA