Although this diploid (2n = 16) winter-annual has become widespread in moist temperate regions of North America, it is curiously rare to absent across north-central regions with more extreme winters and summers (K). Even within the lower Ohio and central Mississippi Valleys, it becomes less common towards the north and west (e.g. Y). In Ky. it was not fully documented until the 1930s, when B reported it only from two northeastern counties (CART, ELLI). It may have been present earlier, but was perhaps confused with Planodes virginica when using available Floras in the 18th Century (e.g. Gray 1864). There has also been some confusion with flexuosa, parviflora and pensylvanica; some colls. need to be rechecked. C. hirsuta varies much in overall size, leaflet size and pubescence, but it consistently has a distinctive basal rosette of leaves, with sparse hairs at least on stem bases and petioles. C. hirsuta has ancient usage as an edible cress but it is generally ignored as such in North America.