Kooloonbung Nature Reserve is a haven of sweet scents

Waxy blossom: The open flower of the bolwarra tree attracts insects such as the brown weevil pollinator.
Waxy blossom: The open flower of the bolwarra tree attracts insects such as the brown weevil pollinator.

Bolwarra (Eupomatia laurina) is a species of shrubs and small trees, growing naturally in eastern Australia and New Guinea.

They are part of an understorey in rainforests and wet eucalypt forests. The tree usually grows to around 5 metres tall, sometimes up to 10 metres. There are two other species, each named small Bolwarra, that grow up to 1 metre.

Bolwarras are quite common in the Kooloonbung Creek Nature Park, so see if you can find some.

A bolwarra tree

A bolwarra tree

The wood has been used in furniture production, and the bark was used for fishing lines.

Fossils from some 90 million years ago indicate a legacy of primeval flowering plants, so the bolwarra is truly a ‘green dinosaur’, and its ancestors would have been eaten by dinosaurs.

It bears creamy-white perfumed flowers in summer. These are very primitive flowers, first going through a female phase in the early morning, before becoming male in the afternoon and evening; this ensures any one tree can’t be self-pollinated.

The white waxy ‘petals’ are actually a collective body called a synandrium which is made up of stamens and stamen-like staminodes, and serves as food for pollinators. Each flower lasts only one day, and after fertilization falls to the ground. Flowers on individual trees, and of individual populations, usually all open together, creating a lovely floral scent in the forest.

Bolwarra is a rare example of a one-to-one plant-pollinator relationship, because all species are pollinated exclusively by tiny brown beetles (weevils in the genus Elleschodes) which are attracted by the fruity perfume. The weevils lay their eggs in the synandria and when these fall to the ground the eggs are carried with them, emerging as larvae and completing their life cycle in the soil.

It is thought this specialised relationship with pollinator beetles arose because beetles evolved in the Triassic era about 200 million years ago, long before bees evolved in the late Cretaceous era (87 million years ago). It is remarkable that the Bolwarra has kept this relationship over that time.

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