The small-flowered touch-me-not, also known as small balsam, is spreading fast in the woods. It is thought to have arrived in the mid-19th century, perhaps with a shipment of Russian timber. A member of the busy lizzie family, its seeds, when ripe, are fired from the long, thin pods with some force; gently stroking a plant will result in a series of audible explosions. Small balsam is mostly pollinated by hoverflies but it can also self-pollinate.
via Melissa Harrison
The Times 30-8-21