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How a grass meadow can boost biodiversity

David Chapman / 30 July 2021

Find out how letting the grass grow can encourage wildlife and boost your garden's biodiversity.

Marbled white butterfly on long grass
The caterpillars of marbled white butterflies, like many other insects, feed on the leaves of grasses

The term ‘meadow’ makes me think of fields full of tall grasses swaying rhythmically in the breeze. I can see a flutter of butterflies pausing to drink nectar from the scattered wildflowers and I hear a skylark singing from on high.

Then I come crashing to earth and think of the rhyme of the man who went to mow a meadow. Why would he do that? Or maybe, more to the point, when and how should he do that? These are the sorts of questions we wildlife-friendly gardeners should be contemplating.

Anyone who has grass in their garden must make decisions about when to cut it. Too many of us revert to a stereotype of cutting once a week to keep it short and ‘neat’. But the key point from a wildlife perspective is that the diversity of habitat is increased if we allow the grass to develop to varying heights.

There is some value to a short area of lawn, mown every week, where else would you find your blackbird probing for worms? Equally there is value to having areas of lawn which are cut only once a month, in here we will be allowing flowers such as daisies and dandelions to produce nectar for bees. But neither of these strategies would create a meadow!

Let’s be honest, the term ‘meadow’ implies a grander scale than most of us can manage in our relatively modest gardens, but many of us have the opportunity to let some of our grass grow longer. It’s the when, how and why that I aim to address in this article.

Firstly I would like to tackle the meaning of a meadow. I think many people see a meadow as being chock-a-block full of wildflowers, and they call it a wildflower meadow. There’s some logic to that but in reality if we let our grass grow longer we will get long grass with only a modest number of flowers: those that can withstand the competition from the grass. We could work hard to introduce flowers but if we don’t have we failed? Absolutely not.

Yorkshire fog
Yorkshire fog has very pretty flowers, an attractive addition to any garden

It’s likely that your garden will have plenty of flowers to provide nectar and pollen anyway and a meadow full of longer grasses provides a valuable habitat for many insects as well as some small mammals and amphibians. As well as adding interest, colour and diversity to your garden these creatures provide food for others higher up the food chain. You won’t have many birds nesting if they can’t find insects to eat, for example.

I’m looking in my caterpillar book and it tells me there are 32 species of butterfly and moth whose caterpillars feed on grasses such as cock’s-foot, meadow grass and Yorkshire fog. They include gatekeeper, speckled wood, wall brown, ringlet, marbled white and meadow brown butterflies and it isn’t a very big book so there are bound to be more.

When deciding where to grow longer grasses, I suggest the best strategy is to form corridors to join together the various wildlife parts of the garden, so maybe have a strip of long grass between your pond and your log pile, or in the corner where there might be some adjoining wildlife-rich habitat in a neighbouring garden or countryside.

If you have a larger garden you could mow a path through a patch of longer meadow grasses. The important thing is that the long grass provides continuity of cover for small mammals and maybe creatures such as frogs which prefer to stay hidden from view. To attract butterflies to use a meadow it would be advisable to have it in full sun, rather than underneath an evergreen tree, for example.

Cock's Foot grass
Cock’s-foot grass plays host to a number of moth and butterfly caterpillars

At some point a decision has to be made: when is it safe to mow the meadow? The answer is a tricky one. Leaving a patch of grass to grow for a month or even two might be enough to allow some flowers and grasses to grow and set seed but it won’t be enough for a butterfly to complete its life-cycle.

Just imagine: you’ve been watching a collection of lovely butterflies flitting around your tall grasses all summer and when September comes the activity ends and you might think it’s safe to take the mower to the grass; think again. The adult butterflies might have gone but if they have done their stuff there will be eggs, caterpillars and chrysalids in the grasses and if they don’t succeed there won’t be any butterflies next year.

So when is it safe to cut a patch of meadow? There isn’t a perfect answer but there are many different strategies and timings and I would employ a variety of them. When you want to cut the grass don’t cut it all at once, cut some of it in the autumn and leave some to over-winter. Cut it to various heights, a higher cut will avoid damaging the caterpillars of butterflies because many of them such as meadow brown and ringlet feed mostly at night and go to ground during the day.

In summary it would be great if we could all allow sections of our lawns to grow to varying heights and we mustn’t worry if they don’t become packed with wildflowers. I think the best strategy for managing these patches of longer grass is to create a mosaic of different heights throughout the year. 

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The opinions expressed are those of the author and are not held by Saga unless specifically stated.

The material is for general information only and does not constitute investment, tax, legal, medical or other form of advice. You should not rely on this information to make (or refrain from making) any decisions. Always obtain independent, professional advice for your own particular situation.