This green leafy specimen has showed up under a couple of lilacs in my backyard. This area was previously strewn with twigs and other debris, carefully cleared my Granddaughter last summer. The area was not seeded, left empty for some Hostas. The 'interloper' is very vigorous, and runs for about a 2-foot length of my west fence. It has been getting sun since the lilacs are still bare. I have dug some out - fairly easy because the soil is quite light back there. Any ideas? Thank you.