We love planting wildflowers in the UK. Bright and beautiful, native flowers are an excellent food source for all sorts of pollinators.
However the lifecycles of butterflies are incredibly complex. These specialist species require certain plants and habitats at certain points of their lifecycle. Not a lot of people realise that grasses are an essential part of that complex lifecycle.
Grasslands are an essential habitat for over 20 species of UK butterfly (out of 59 species). However 90% of the lowland grassland in the UK has been lost and there is only a small proportion of unimproved grassland left (hasn't been reseeded, drained or fertilized) (1).
Many butterflies rely on stems, leaves and seed heads of specific plants for egg laying and even overwintering. Marbled whites, a butterfly seen from June-August in the UK, have a curious behaviour of perching on stalks and dropping their tiny 1 mm eggs into the grass. Unattached to any stalk, the egg remains at the base of the plant, on the ground, for about 20 days before emerging into a caterpillar. Here, the caterpillar will remain in a grass clump until Spring (2). Red fescue is a particularly important noted grass in caterpillar feeding but the range of grass species eaten is unknown (3).
Other butterflies such as the Small Skipper lay their eggs in the sheath of the foodplant. When the caterpillars hatch, they spin a protective sheath around themselves and remain at the base of the plant for hibernation. It is essential that the grasses aren't cut overwinter for the survival of this species.
In gardens, providing a nectar source only benefits most butterflies for a small part of their life cycle - the adult stage. While a short, frequently mown, "neat-looking" lawn is not going to do a lot for butterflies, leaving grasses to grow tall and encouraging native grass species is a great way to support butterfly populations for their whole lifecycles. And it means less garden work!
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