One of three major types of cannabis along with sativa and indica, ruderalis has the distinction of developing buds at a very early stage of growth regardless of the light cycle. Consequently, it only ever gets about a foot high. Although normal ruderalis plants have virtually no THC, there are hybrids that have most of the bud quality of regular weed, with the early budding of ruderalis plants.
You've got weed already? You just planted your seeds two months ago!
Yeah, it's a ruderalis hybrid. Not the best stuff you'll ever smoke, but better than Mexican brickweed.