Curly whirlies

Himalayan balsam is a much-reviled invasive plant that has established itself along our waterways. Despite its attractive pink flowers, and the fact that bees love it, much time and energy has been spent 'balsam- bashing', to little effect.  We're stuck with it now.

The explanation for its success lies in these little coiled green springs. They are exploded pods, the seeds having been expelled with so much propulsive force that they  can scatter 20 feet or more, often into running water that carries them further down the river bank. The ripening pods as they dry out are under such extreme tension that a puff of wind or a light touch of a passing animal or insect is enough to set them off. If you gently squeeze  a pod it feels like  a grasshopper jumping in your hand. A single catapulted seed is enough to trigger another pod and the domino-effect results in a shooting gallery of explosions. It's great fun to do but be careful you don't accidentally carry any seeds home in your clothes or you'll have Himalayan balsam all over your garden.

(Most parts of it are edible; there's a recipe for using the seeds for a curry here.)