Lawns

Life at ground level

David Beeson

We often ignore our lawn biologically. Some humans, normally males, obsessively cut and de-weed their lawn and a few, poor creatures, spend time putting stripes in it. Others are idle and leave the green space to grow tall until a towel is thrown down so the occupant can sleep away the day in the sunshine. As people, bright enough to appreciate the natural world, us, wildlife enthusiasts, can see the lawn through enlightened eyes.

Natural lawns are uncommon in nature. They occur where grazing pressure keeps the natural vegetation cut to near ground level.

Immediately the chalk downlands and fells of the Lake district spring to mind. Care here. Are these natural or man-made? Both, I would suggest, are due to a vast over-population of sheep. Economist now suggest, an uneconomic excess of sheep that will soon be swept away by the removal of agricultural subsidies.

Knepp may be establishing some semi-natural lawns in its rewilding, and some will occur where nutrient levels are minimal or the climate is extreme. But, lawns with their grassy swards are mostly human made. That, regardless, does not make them uninteresting.

So, what do we have in our obsessively mown lawns?

It’s grass. Well, some of it is grass, especially if the area is ‘weed killed’ and treated with fertilizers. But, let’s start with the grass.

Grass is important. Grasses occur almost everywhere on land. With light and moisture at ground level, if you seek them out almost anywhere you’ll encounter a grass plant. It may well not be one of the species in your lawn, but one will be there. And, some of them are clever enough to encourage humans to look after them. Think of the hectares of land planted with oats, wheat, barley and rice. They are all grasses – members of the grass family – GRAMINEAE.

Plants grow from specific areas called MERSTEMS. Most human cells can grow, but that is not the case with plants. Their meristems are often only located at the shoot tip, root tip or towards the outside of a stem (the cambium, for example). Grasses, however, are unusual. They have a very useful adaptation to being grazed or mown – their stem meristems are in nodes along the stem and NOT at the tip. Look at the swellings along a well-grown grass stem: these are the meristems. This is where the grass grows. Cut the top off a grass plant and it keeps on growing from these nodes. Chop off the stem of a non-grassy plant and it takes ages for side shoots to develop, grow upwards and so recover.

Grasses are not leguminous – they do not have podded seeds and nitrogen-fixing bacteria in root nodules. Hence, they grow most vigorously in nitrogen-rich soils. So, if you fertilize your lawn the grasses grow rapidly. If, like me, you never do that and remove all the lawn cutting to a compost heap the grasses grow poorly. That leaves room for plant diversity.

Good, biologically diverse lawns and hay meadows occur on nutrient-poor soils.

Evolution has had a few millions of years to generate plants that can survive in amongst grazed grasslands. They are particularly plants that keep their heads down for much of their life or are sneaky.

Look at clover. Its stems creep along the soil, protecting its meristems from chomping. It is a legume, so makes its own nitrates. Daisies have leaves flattened to the soil, avoiding cutting, and only throws up its flowers skywards. Meadow saxifrage hides below ground from summer until spring and still keeps a leafy low profile. These are some of the clever strategies of plants that were once very rare … before humans stared mowing lawns and over-grazing areas.

Remove the grazers or the lawn mower and we’ve all seen the results. The seedlings that previously were eaten to death by the removal of their tip meristems can now develop. Taller plants take over the sward, hawthorn, bramble and seedling trees grow and survive. The grassy area starts through succession that could cause the patch to develop into scrub and eventually woodland.

For folks interested in wildlife, a diverse lawn provides habitats for many animals. Give nature a sporting chance – don’t feed or over-cut you lawn. Have a flowery lawn and you’ll notice the difference.