OVER the centuries man has introduced many plants from abroad, some of which have proved most invasive.

Notable among these are Japanese knotweed and the sweet-scented Himalayan balsam brought over in 1839 and which runs riot along stream sides. Bees love it though and emerge from the flowers covered in white pollen.

There are two introduced species that have proved most beneficial and colourful to our flora.

The first is Michaelmas daisy. I welcome it as summer comes to a close and when most other flowers have faded. Belonging to the aster family, it was introduced from north America and is now widely naturalised among several varieties which as well as being a delight to the eye, offer late insects a nectar feast.

The second introduction is buddleia, a native of China that arrived here at the end of the nineteenth century.

The wild variety sports long spikes of lavender/purple but cultivated varieties come in white or dark mauve. Buddleia can grow anywhere from waste ground to railway embankments, hedgerows and even on rooftops wherever seeds take root.

Faintly scented it has earned the very apt alternative name of “butterfly bush” as it attracts peacock, red admiral (pictured), small tortoiseshell, whites and comma butterflies from mid-summer onwards.

The sight of a buddleia adorned with a host of feeding butterflies is seen less and less these days as many apart perhaps from the comma, the other species have suffered a steady decline in recent years.