Hello,

The weed in the picture is Red sorrel, Rumex acetosella. it is a rhizomatous perennial spreading by the rhizomes underground. The plant has extensive buy shallow root system consisting of a yellow taproot and numberous slender rhizomes. Plants accumulate high concentrations of soluble oxalates, which give them a sour taste and occasionally cause fatalities in livestock, particularly sheep.
Control can be had by applying a broadleaf weed killer.

Regards,
Carol Quish
UConn Home and Garden Education