Backyard Buddies
Trigger Plant

Photo: John Tann

Trigger Plant

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The Trigger Plant gets its name from its unique pollination method.

When an insect investigates a Trigger Plant flower, it is hit with a club-shaped column that quickly springs up from under the petals. The insect's feeding activity disturbs small filaments in the centre of the flower, activating the column. On the end of the column are male and female flower parts. The male parts deposit pollen on the insect, and the female parts can be fertilised by pollen on the insect if it has already been hit by another Trigger Plant.

Different species of Trigger Plants hit different body parts of insects, and this helps reduce the risk of self-pollination or hybridisation between Trigger Plants.

This means that an insect feeding on one species of Trigger Plant may be struck on the head, and when feeding on another species, it might be struck on the side. This enables the right pollen for the species to be deposited or collected by other Trigger Plants because head-clubbing Trigger Plants will collect pollen from other head-clubbing Trigger Plants, and side-clubbing ones will get pollen from other side-clubbing Trigger Plants.

Trigger Plants are fascinating to watch. People can trigger the same explosive reaction as insects by tickling the inside of the flower with a bit of stiff grass. Once triggered, the column needs about an hour or more before it can hit again.

One of the commonest species is the narrow leafed Trigger Plant Stylidium graminifolium, which is quite widespread in Australia and Tasmania from coastal to near alpine regions.

The flowers of this species are mostly pink, but some white forms occur. The flowers are arranged on stalks which can be up to 40-50 cm high. Flowering time is from spring through to summer.

Did you know? 

Around 70% of the known species of Trigger Plants worldwide occur in the south-west of Western Australia. This region is the major centre for evolution of Trigger Plants.

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