Oxalis weed, or Oxalis corniculata, is a creeping perennial that is typically mistaken for clover due to its shamrock appearance, according to Colorado State University. Oxalis weed is commonly found in thin turfgrasses.
The oxalis weed has small yellow blooms and green leaves that will appear purple in the fall season. The leaves close up at night or during overcast days. After fruiting, its seeds will scatter everywhere. Propagating is done via layering, as it will take root whenever its stems touch the ground. Oxalis can be less of a problem when lawn grasses are dense and the watering is not too frequent.