Trifid

What sharpness!!!!

Not quite a Triffid but almost as nasty. This is Himalayan (or Indian) Balsam, a foreign and highly invasive introduction which chokes and out-competes native species especially along river banks. It is certainly on a government list of undesirable aliens. Kill! Gently squeezing a ripe seed pod will result in a quite spectacular explosion which throws the seeds a considerable distance.
Best regards Fraser