One of the more common plants on grassland where the ground is undisturbed is the common sorrel (Rumex acetosa). When one looks at the flower heads which are loose spikes of individual reddish brown flowers it is immediately obvious that this is a member of the dock family - most docks bear the name rumex.
Flowering from May until July the flower heads are visible long after this when bearing the seeds. Common sorrel can grow to almost three feet tall but this is rarely the case and a foot to eighteen inches is, perhaps, the norm. The leaves are absent from the upper reaches of the flower spikes and can be found further down the stem. At school we used to bite the leaves to release a taste akin to vinegar, indeed we called them the vinegar plant and that is, of course, where the acetosa part of the name comes from, acetic acid or vinegar.
In the middle ages it was grown as a food crop but this is no longer the case; the leaves were once used in salads but the presence of oxalic acid can cause problems for some people with certain conditions. It also has some traditional herbal uses but more recently it has been used in research into treatments for cancer and sinusitis.Common Sorrel: the vinegar plant