That looks like sheep's sorrel, Rumex acetosella. Grows in pastures, fields, dry areas and is much smaller than French or Garden sorrel. It has a peppery, lemony, astringent flavor and is quite tasty in salads!
I would agree with this photo of Sheep's Sorrel (Rumex acetosella), unless it fell into the category of Common Sheep Sorrel (Rumex acetosella subsp. acetosella), for which there are no photos.
