It's a noble caper
The Noble Caper sounds like a hoity-toity British bank-hoist film, or perhaps something pretty exotic to eat. In fact its one of the vernacular names for an Australian native plant loved by butterflies, Capparis arborea.
It’s more commonly called the Native Pomegranate, but also Wild Lime or Wild Lemon.
We have mature specimens in our Rare and Threatened Garden, near the walled Cacti and Succulent Garden. Their fluffy white flowers in December and early January are a magnet for white butterflies.
The Caper White is the best known of these insect visitors. It migrates northwards every spring and early summer, with sometimes thousands swarming around caper trees.
Research Associate with the Australian Museum, Dr Courtney Smithers, says it sometimes gets carried into Sydney on the hot North-Westerly’s, from inland of the mountains where most of the caper trees live.
Dr Smithers has been monitoring the movements of butterflies over many decades and is about to publish his results on changes in their behaviour and range that might be slated home to climate change. The Caper White, though, has probably always found its way across the ranges every now and then.
The Pearl White is another butterfly with a penchant for capers. It will feed on other flowers, but usually not more than 20 m from a Capparis. Eggs are laid on the leaves and the caterpillars munch their way through some of the foliage but usually not enough to cause the tree any long-term harm.
Our native Caper has been in the gardens since at least 1884, and so have the Pearl Whites. Like the Caper White, Sydney is not part of the natural range of the Pearl White. It tracks this species of Capparis from rainforests in the Torres Straight Islands south to about the Hunter. But our specimens of Capparis arborea are enough to draw it into the city.
The fruits you can see swelling on this native caper now, in February, have a sweet pulp that is eaten by Aboriginal people, a fact noticed and imitated by early European settlers. However the capers most people consume today are the pickled flower buds of the Mediterranean Capparis spinosa, another of the 250 or so species of this genus worldwide.
The green seed-pods of Nasturium are sometimes eaten as a kind of poor man’s caper, but they are certainly not up to the standard expected by discerning blog readers or butterflies.
Image: the attractive caper flower in Sydney's Royal Botanic Gardens. *This posting is from the Radio Archives (February 2009).