Thursday, 21 January 2010

Bamboo's Final Fling?



We have two bamboos in flower in the Oriental Garden at Sydney's Royal Botanic Gardens, both of them in the genus Bambusa.

Bambusa multiplex is just finishing but Bambusa ventricosa (also known as Buddha's Belly Bamboo due to the bottle-like swellings of the cane when stressed) is in full flush. Intrepid botanical observer and Acting Manager of the Royal Botanic Gardens at the moment, Simon Goodwin, wonders if the loss of leaves on the flowering plants of Bambusa ventricosa means it is 'monocarpic'.



I've posted before on where bamboos come from and our local species, but not about their odd flowering cycle. Plants that flower once are called 'monocarpic'. It's commonly thought that bamboos are not only monocarpic but that a whole population flowers, and dies, together.

It does happen. Widespread die-off following a mass flowering of one of the Australian species (Bambusa arhhemica) in the late 1990s was assumed by many locals to be part of a weed eradication program by land managers. In fact it was part of a natural cycle. Over 80 per cent of the population flowered and died during an eight-year floral orgy.

These cycles vary in length depending on the species, and can range from one to 120 years. The reasons for the long flowering cycles in some species may be an evolutionary strategy to overcome predators eating all the seed—you save up all your energy and blast out so much seed they can’t eat it all—or perhaps they are triggered by longer-term environmental conditions.

After flowering, some bamboos die; others are weakened for a while and will recover; while those that flower more frequently (for example, annually) continue to grow quite happily.

In horticulture, simultaneous flowering may also occur because we grow vegetatively propagated plants from the same source and of the same age. In some areas where the stock all comes from the one nursery, the flowering becomes more or less cyclic (and the odd exception is overlooked).

If you want to observe some different species for yourself, we have 40 or so growing in the Royal Botanic Gardens, many of them in the Oriental Garden.

Image: Flowers of Bambusa ventricosa earlier this week (close up by me, habit by Simon Goodwin). Will these plants die after flowering?

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