Yellow wood sorrel
(Oxalis stricta)

Native. This small, weedy plant is abundant in lawns and disturbed areas. Note the sharp angle between the upright seed pod and its stem, unlike that of the similar O. europa. MC (Oxalidaceae)

Yellow wood sorrel
(Oxalis europaea)

Introduced. Very similar to O. stricta, above, but note the lack of a sharp angle between the peduncle (fruit stem) and the seed pod. MC