or the freakishly mild winter of 2011? This week i went up top to make sure the tarps surrounding the bins were secure, and found dozens of bins overrun with chickweed. The brown scraps are degraded maple leaves that were salvaged in the fall, packed into green garbage bags and volleyed onto the roof from the alley. The maple leaves act as a blanket mulch, insulating the soil surface against the cold, and eventually breaking down into free mineral nutrients. If worms in the bins haven't succumbed to the freezing temperatures(?), then those invertebrate tenants will metabolize the leaves into fertilizer.