Oxalis violacea, Violet Woodsorrel
Native, Piedmont & coastal plain

Oxalis corniculata, Creeping Woodsorrel
Non-native, Piedmont & coastal plain
Creeping, rooting at nodes.

Oxalis stricta, Upright Yellow Woodsorrel
Native, Piedmont & coastal plain
Long hairs on the stem.
(sparsely to very sparsely pilose with nonseptate hairs or a mixture of nonseptate and septate hairs or densely villous with septate hairs)

Oxalis dillenii, Southern Yellow Woodsorrel (O. florida)
Native, Piedmont & coastal plain
No long hairs on stems, just short hairs that lie close to the stem.
(Stems evenly strigose from base to peduncles and pedicels)