Lesser Celandine and Japanese Knotweed

 

Superficially, Lesser Celandine (Ranunculus ficaria) -- the carpet of yellow flowers -- looks like a pretty wildflower, but it is a very serious non-native plant invader in Arlington, taking over low areas and crowding out native wildflowers like Spring Beauty. It leafs out and blooms very early, and then by May or June it has vanished until the next year. The plants produce many tiny bulbs that can move downstream to start new infestations, and make it almost impossible to eliminate by pulling since bulbs are left behind. Also seen in the photo is a young annual shoot of Japanese Knotweed (Polygonum cuspidatum or Fallopia japonica), another serious invader of wet areas. It seems often to be spread by contaminated fill dirt and digging equipment, and can often be found where heavy equipment has done work. Japanese Knotweed creates dense patches where nothing else grows. Just to make things worse, this infestation is in a rare "Magnolia Bog," endangering the unique natural plant community of the bog.