|Hairy Bitter-cress: Cardamine hirsuta|
Look at this fighter flowering already in January. It's secret weapon is the speed of reproduction and explosive seed dispersal. Brush against the plant when the seedhead is ripe and you set off a shower of projectiles, each one an irretrievable seed (on account of it's small size). Ballochory is the term for this - my new word of the day (and not to be confused with barochory which is seed dispersal by gravity alone). Hairy Bitter-cress appears first as a rosette before sending up a number of stems which rapidly produce unprepossessing flowers. Once primed the seed head reacts to your weeding efforts as a stimulus to explode. "You are too late" it says as it peppers your face with pellets. Moral - weed early, preferably at the rosette stage.