Weeds of the Balcony

I've been taking a very relaxed approach this year to weeding the planters on my balcony. Crazy? Perhaps not so, given that I'm more inspired by what I find growing in abandoned lots, parking lots, and in the wild, than in "nicely maintained" gardens. So I'm genuinely curious about what these volunteers will grow up to be.

Robin's Plantain (Erigeron pulchellus)

I am also hoping that some of them are offspring of the dried Misanthus sinensis stalks I stuck in one of the cedar planters last fall.

I am sure so far that I've identified a variety of smartweed based on leaf shape and hairlessness and the presence of ocreae (membranous sheathes where branches emerge). Initially, I thought it was Polygonum persicaria, or Lady's Thumb, based on the characteristic blotch on the leaf (presumably, the thumbprint of a lady with sooty hands).

However, the ocreae in Lady's Thumb are fringed with hairs and my specimen is decidedly unhairy all over. Despite the presence of the blotch, it is likely that my specimen is the very similar Pennsylvania Smartweed (Polygonum pensylvanicum) or Green Smartweed (Polygonum scabrum). An ocrea is a membranous sheath that surrounds the point where a stem branches off.

Unhairy ocrea rules out Lady's Thumb

In any case, the adult plants of the possible species are all pretty uninteresting looking (and too big for the front of the planter), so it gets yanked.

Back to its roots

I stumbled on the initial Lady's Thumb ID by opening every weed name link in Québec's weed identification guide and seizing on the one with the picture of a blotchy, elongated leaf. But it's been pretty hard going when doing a directed search based on the observed characteristics of immature plants. There are many weed ID sites with indices of common and Latin names, but few (such as this one from Michigan State) offer a key-based approach to identification.