From the CO2Science.org archive: Rumex obtusifolius L. or Bitter Dock, also known as broad-leaved dock, bluntleaf dock, dock leaf, dockens and even butter dock, is either an invasive weed or a tasty salad green (or both) depending on whom you ask. It grows throughout the world, and as the amount of CO2 in the air rises it will grow even better. In 1998 there were six experiments showing that an extra 300 ppm CO2 causes Bitter Dock to grow an average of 18.7% bigger. So if the dockens is growing like the dickens, you’ll know why. Just don’t be bitter on your dock.