Impatiens glandulifera

Or Himalayan Balsam. It is an invasive weed but I do think the flowers are rather lovely and I am dreadfully irresponsible because I take huge delight in 'setting off' its seed dispersal system.

Wiki says: After flowering between June and October, the plant forms seed pods 2 to 3 cm (¾ to 1¼ in) long and 8 mm broad (¼ in), which explode when disturbed, scattering the seeds up to 7 metres (23 ft). Impatiens, meaning "impatient", refers to this method of dispersal. The green seed pods, seeds, young leaves and shoots are all edible.

What completely fascinates me is how plants develop such sophisticated dispersal mechanisms. If you look at the photo above you can see a pod which hasn't popped yet, it is long and slender. When touched this pod will pop and sections of it very rapidly curl up and fire out the seeds resulting in the blown pod which is in focus. After much experimentation *ahem* daughter now looking at me with disgust as I've just asked her to hoover up all the seeds in the 30' living room it would seem that the lighter green stripes are somehow grown under tension and when the pod is released these are the bits which snap back.

Great fun and a really fascinating plant.