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The Whys and Wherefores of Plants

by Martyn Stead, who leads the Wildflower Walks around Caldy Nature Park.

Plants were the first to colonise this planet and they have evolved to survive in a wide range of conditons. They can tolerate extremes of temperature - there are lichens in the Antartica, a species of willow grows no higher that 4 inches in the Arctic and pebble plants in the Namib Desert survive by living partly underground.

Humans have always attempted to control plants. Gardeners know the joy of having to pull up the annual weeds and they have developed strategies to control their growth by putting down a mulch to suppress the weeds or use ground cover plants.

How do these plants get there in the first place ? One of the main ways is by seed dispersal, which really is the old chicken and egg story with a twist. Many plants, once established, have evolved ingenious ways of regenerating themselves, e.g. by stolons, rhizomes and bulbils.

Having looked at a few hundred ponds, I would say that there are very few that are identical. This diversity of plants gives rise to a diversity of insect life and then bird life. Plants that grow on the water's edge are hungry for water and the nutrients suspended in the water. Reeds and bulrushes that grow at the edge of water can only survive to a certain depth. The deeper the water, the lower the light levels and if a plant is too deep, it cannot produce enough energy from its stock to reach the surface . Anything or anyone can get out of their depth.

I have looked at many places of interest over the years and the same old question will arise from time to time. Why does a plant grow here and not there when the surface conditions seem to be the same. There could be just a minute change in the microclimate or a missing nutrient. Who knows ?

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