‘No Mow May’ has become something of a mantra over the last few years but is it really the panacea it’s made out to be? As ever, things are slightly more complex and require a more nuanced approach. In principle, putting the mowers and strimmers up for the month of May and letting the grass and flowers grow is a good idea. Lots of pollinating insects from bees to butterflies will benefit from allowing native wildflowers to flourish in our gardens, churchyards, parks and verges.
But all too often, come June, the mowers are back out with a vengeance, the flowers are shredded so the insects waste valuable time and energy flying to a spot that used to provide pollen and nectar and any invertebrate that had the temerity to set up home in the long grass is now homeless.
Road verges are usually mown to help with visibility, especially on narrow country lanes. Where the verge is wide enough the grass can easily be cut short by the roadside and left long at the back, especially if it joins a hedgerow as it will provide cover for invertebrates as well as birds and small mammals.
One size doesn’t fit all
Now, I love a good lawn but by that I mean a short green sward studded with the sparkling flowers of dandelions and daisies. On a sunny spring day these humble flowers will be buzzing with solitary bees, hoverflies and butterflies. Short grass is perfect for several species of mining bee to nest in too. Discreet small holes in a lawn may have Andrena nitida nesting in them but if there is a little cone of loose soil it is probably the Tawny Mining Bee Andrena fulva who has set up home. Our lawn is also dotted with patches of white clover and the tiny pink flowers of dove’s-foot cranesbill. Left uncut, these flowers can grow up into tall straggly plants but they will happily flourish in a shorter sward; just mow less often to encourage them then set the blades a bit higher so the blooms aren’t lopped off. Some birds – notably starlings – like areas of short grass to forage on, jabbing their beaks into the soil to get at beetle and cranefly larvae.
Where space permits though, let the grasses grow tall and allow the wild flowers to spread their stems and leaves upwards to create a miniature jungle for a whole host of invertebrates that like a tangle of leaves and stems to thrive in. Several of our butterflies lay their eggs on grasses, including the Meadow Brown, Gatekeeper and Ringlet whose caterpillars hibernate over the winter, so need long grasses all year round. If you cut your grass in June then you could well be destroying the next generation of some of these butterflies. Likewise, if you keep an area of longer grass throughout the summer months you will find all sorts of insects taking up residence from plant bugs to bush-crickets. You will find a variety of spiders like the longer vegetation too from the Cricket-bat Spider Mangora acalypha (named after the pattern on their abdomen) to the Nursery Web Spider Pisaura mirabilis whose females spin a web for their egg sac and then sit guard over it until the little spiderlings hatch out.
Not all grasses are equal
We are lucky that our garden has light sandy soil which is very low in nutrients. When we don’t mow our lawn, we have a suite of nice wildflowers but depending on your soil type you may just get grasses. You can add pot-grown wildflowers and make your long grass area into more of a wildflower meadow. The one critical thing that often gets missed (or left, in fact) is what happens once the grass is mown. All too often, especially in parks and on verges, the grass cuttings, known as arisings, is left in situ once the mowers have passed through, where it then rots down and enriches the soil. Most of the wild flowers and fine grasses that we associate with meadows like low levels of nutrients. When the arisings are left, the continual yearly enrichment favours tougher grasses and we quickly lose the species richness. This makes the grassy areas far less attractive both to us and to the insects we have been trying to help and encourage with No Mow May.
The long and the short of it
In summary, the worst practice is to not mow in May, cut everything down in June and then leave the arisings in place. The best grass and meadow habitats we can create are those that have a mosaic of different heights and have plenty of edge habitat; paths of short grass around or through longer vegetation provide lots of edge habitat where insects can bask or feed in the open but then dive for cover if danger threatens. At summer’s end when flowers have set seed it is time to cut but, if you can, leave a few areas tall so that any invertebrates can scuttle into it and spend the winter. The most important thing at this stage is to rake up the cut grass.
And once you’ve raked up the arisings, layer them up in the compost or, better yet, start a grass pile in a corner of the garden. As the heap slowly decomposes a new suite of fascinating invertebrates will start to appear. But that’s a whole new article for another time…
