November 22, 2017

Caroline’s Garden Diaries 4 March 2017: Grand Designs

Another bonus of being in Sydney in late summer is that Magnolia grandiflora are just coming into flower and I get to walk past them every day. They’re beautiful, but they’re also giving me a lesson in botany. I’ve been able to see what goes on within the flowers because the trees down our street are only adolescent, sexually mature but not so tall that I can’t see the flowers. Feels a bit rude really, but my attention was drawn to them by seeing a wasp (bee? I don’t know Aussie insects) fumbling around in a pile of stamens, while in another flower, a similar bee/wasp was undressing the female part of the flower by tearing off the stamens (well, flowers are about sex).

“Grandiflora”, yes, but we can’t really call them “grand design”; they’re the product of the marvellous Darwinian process of natural selection. Magnolias are particularly interesting in evolution because they are one of the first plants to develop flowers as a way to persuade beetles to visit (bees came on the scene later) and help them with the difficult business of getting pollen to the female parts, and thus to accomplish fertilization. This enormous scented flower signalled to the beetle that here was pollen to eat (no nectar yet, other flowers worked that one out); the beetle who was itself evolving and needing a way to make a living, came, scrabbled around in the stamens, and bumped into the female structures – and the rest is history.

A brilliant consequence of evolving flowers to please insects is that we humans are seduced too; to quote from a book I’ve just bought “those who are forming gardens should always give magnolias their first consideration when planting”. What a grand design on the part of magnolias, to plan for 90 million years ahead! Take that, Kevin.