Derek – Friday 20th November 2020
Scattered about the garden are sycamore helicopters. Picked up by the wind, they twirl away from the parent tree. Though many lie at the foot, rather uselessly, as if they were to grow, they would be so overshadowed, they’d fail to make maturity. In truth, none will in our garden as we’ll sweep them up, and pull up any seedlings we find.
All plants must disperse their seeds, if they are to have offspring. Wind is the most common mechanism. Used by the sycamore helicopters, and most obviously in the dandelion family, the compositae. They have their fluffy parachutes or wind fairies. We assist them when we blow dandelion clocks, scattering the seeds to the chance of the breeze. Thistles have their cotton wool-like tufts, as we witness in our wildflower bed. Another in the bed of that ilk is bristly ox tongue, the yellow flowers destined for a similar floss which will head off on the wind.
Animals, including ourselves, are used in seed dispersal. Berries are eaten and pass through the gut and out with faeces. Or plum stones are spat out. Or they stick to animal fur (or our clothing) like the burrs of burdock with its velcro-like hooks. Or cleavers, which have hooks on the stems and the animal pulls them away, stem and seed attached. When I return from a country walk, I often wonder what seeds are in the mud on the bottom of my boots.
On our pond, you might see tiny discs floating, like roulette chips for leprechauns. They are the seeds of the water iris (or flags). In a stream, they are dispersed by floating off to some far bank. They make me think of the coconut which Miss Gould taught us floated across oceans in their search for fresh beaches. All the matting around the nut makes them buoyant, but disappointingly, sorry Miss Gould, while this may take a nut to a nearby island, research has shown not much further.
I am fascinated by volcanic islands thrown up in eruptions in the oceans. They are initially barren, with no life at all on the hot lava. But once cool enough, plants arrive across the sea, the seeds brought on the winds, floating in the sea, or in the feathers or feet of birds as they stopover. Darwin did experiments with seeds in seawater, and found some survived many months.
Buddleia davidii is a plant par excellence when it comes to dispersal. Its seeds are windblown, millions from a single plant, but also attach to birds and animals or float down streams. The plant doesn’t miss a trick. Buddleia was brought to the UK from China in the 1890s and how well it has proliferated. Called familiarly the butterfly bush, it is both welcomed and hated. When this garden was being cleared in 2015, lots of it had to go, but we left our big patch, being good for butterflies, birds and children to play in. I am always intrigued to see buddleia growing on high walls. A seed has landed in the cracking mortar, finding enough sustenance to take root.
Join the discussion and tell us your opinion.
In terms of seed dispersal, look up Kopi Luwak, the most expensive coffee in the world as the cherries have passed through a civet first. Saw it in Indonesia but didn’t fancy it!