wow...this stuff is taking over! Polygonum perfoliatum was first recorded in oregon in 1890 and then in beltsville, maryland in 1937: both "mile-a-minute" weed populations were eradicated. it popped up between the 1930's and 1946 at a rhododendron nursery in york, pennsylvania and was kept and studied by the nurseryman. this invasive non-native plant species is now found radiating 300 miles from the york nursery. i took this shot in rock creek park today. vine-y!