Butterfly bushes

Purple hairstreak credit Mathew Frith 

Guest blogger Amanda Tuke reflects on the mixed blessing of Buddleia davidii, the butterfly bush.

Early Sunday morning I pause at the Buddleja bush growing to the side of the old rail-bed in Sydenham Hill Wood. The crackled main trunk has arched over and lateral branches have grown up through the brambles to reach the small patches of light.

The sweet-scented flower heads are beautiful, mauve mini-trumpets contrast with a zinging orange eye in the centre, but this butterfly bush (Buddleja davidii) brought from China by the Victorians is non-native in Britain. It forms vigorous clumps along railway tracks, on derelict buildings and waste land, out-competing native plants.

Even it’s value as a nectar plant for butterflies and moths has a downside as it can smother the caterpillars’ food plants.

Purple buddleja in flower

Butterfly Bush (Buddleja davidii) - Amanda Tuke

The good news is there’s a solution for gardeners who don’t want to add to the problem. There are a number of cultivars of buddleja which provide the nectar to attract insects but don’t have the wild plant’s weedy habits.  Failing that, if you already have a buddleja in your garden and you can’t bear to lose it, then deadheading it when the flowers are over will stop seed dispersal. Even better if you can also have a patch in your garden where wildflowers grow to support caterpillars.

This morning I’m surprised to see there isn’t a single insect visible on this buddleja. Round the corner though it’s a different story - the Traveller’s Joy is in flower and fluttering. This native butterfly bush provides nectar but is also the food plant for the caterpillars of a number of moth species. I see a red admiral, battling meadow browns and then dropping down from the trees above, this purple hairstreak. He doesn’t hang around for long though before disappearing back up into the canopy.

Purple hairstreak butterfly on leaf

Purple hairstreak - Amanda Tuke

Butterfly Conservation's Big Butterfly Count takes place from 17th July - 9th August. Visit their webpage to find out how you can take part

Find out more about London Wildlife Trust's own Brilliant Butterflies project

Follow Amanda’s blog at www.suburbanwild.wordpress.com