Wood Sorrel

Oxalis stricta

 

This herbaceous plant may grow either as an annual or as a weak perennial. Although it prefers moist soil, and partial shade, it is tolerant of a wide range of conditions. It is commonly found in fields, woods and borders, along roadsides and in other waste areas, and will even grow in the cracks of sidewalks. It is also a common summer annual in lawns. As one of the latest germinating annual weeds, it often fills in spots left in the turf after broadleaf weeds are killed by early spring herbicide applications.

The delicate-looking plants grow 6-15" tall – unless they are mowed off consistently in a lawn. They may form colonies arising from slender but tough underground stems (rhizomes), but more often are individual, seed-grown plants. The weak stems branch at the base and sometimes will root at nodes.

Leaves are alternate, smooth and palmately compound. Each leaf is divided into three heart-shaped leaflets similar to a clover leaf, with faintly hairy margins. The leaves are creased and fold upward in half at night or when stressed (such as if picked or during storms). Most plants are green, but some have a purple cast.

Common yellow woodsorrel is best controlled by hand weeding and mulching. It pulls up quite easily and does not resprout from roots left behind. Try to remove plants before seed pods develop – although this may be difficult as it is good at hiding among other plants, producing seeds before it is ever noticed. Most herbicides are not very effective on Oxalis species. Pre-emergence herbicides, which prevent germination, are the most useful.