The importance of buddleia – and nettles – in our gardens

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A regular column from the Lincolnshire Wildlife Trust’s Rachel Shaw.

Last week I was walking through town and passed an empty pub with its windows boarded up.

Plants were already reclaiming it as their own. The most dominant was buddleia, the common garden plant also called the butterfly bush.

The air was filled with the honeyed-aroma of the large drooping spikes of purple flowers. The scent had certainly worked in attracting insects. Bumblebees and a variety of butterflies including peacock and small tortoiseshell were feeding on the flowers. It is, of course, the plant’s popularity with butterflies that gives its alternative name and one of the reasons why it is so commonly planted in gardens, though buddleia is now commonly found outside of gardens.

Buddleia seeds are adapted to germinate in the harsh rocky conditions of their native China. The seeds are small and have wings to aid their dispersal in the wind. It means buddleia is particularly well adapted to colonize waste ground – it grew on bomb sites and building rubble after the Second World War, and spread along railway lines.

While buddleia does provide a very important nectar source for butterflies and other insects, particularly in the urban areas, it doesn’t provide food for caterpillars and shouldn’t be seen as a replacement for naturally occurring wildflowers. Nectar-rich wildflowers such as Lady’s bedstraw, knapweed, field scabious, red champion, common mallow and purple loosestrife are all great additions to the garden.

However, to really help butterflies, we need to have plants for young butterflies – for caterpillars.

Over the last few days, I’ve seen a female holly blue butterfly flying in among the ivy leaves that cover my garden wall and I suspect she’s looking for places to lay her eggs. While the adult butterflies will feed on the nectar of a range of flowers, the caterpillars (just like children) are fussier about what they eat. Holly blue caterpillars primarily eat ivy and holly leaves.

The caterpillars of different species of butterfly favour different food plants. Even the humble nettle is an asset in the garden, especially if grown in a nice sunny spot, because the caterpillars of peacock, small tortoiseshell, red admiral and comma all feed on nettles. However many buddleias find a foothold across our towns, without nettles there will be no peacocks or small tortoiseshells to feed on the nectar.