Pennsylvania Smartweed: Polygonum pensylvanicum
Seedlings: Cotyledons are elliptic to lanceolate in outline, whit hairs along the margins. First true leaves are alternate, lanceolate in outline, and hairy on the upper surfaces.
Fruit: A black achene.
Identifying Characteristics: The elliptic to lanceolate leaves with a purple spotted 'lady's thumb' print in the middle and distinctive ocrea are all characteristics that help to distinguish Pennsylvania smartweed from other similar weeds. Ladysthumb (Polygonum persicaria) is very similar in appearance and growth habit, but has stiff hairs on the ocrea that are approximately 2 mm long unlike that of Pennsylvania smartweed. Tufted Knotweed (Polygonum caespitosum var. longisetum) is also similar in appearance and growth habit, but has hairs on the ocrea that are much longer (5 to 10 mm) than those of ladysthumb.