yellow wood sorrrell also known as Creeping Oxalis
 

Creeping oxalis (Oxalis corniculata).

Creeping oxalis is an annual or sometimes perennial herb, and is also known as Yellow Wood Sorrel or Wood Sorrel. It is a weed of gardens and lawns, and has three leaflets on each leaf. Often this troublesome weed forms dense mats in lawns that choke out turf.
 
 
It is often confused with Soursob, Soursop or Creeping Buttercup (Oxalis pes-caprae), which does not have creeping above ground stems and reproduces mostly via underground bulbs. This flowers mainly in Winter and goes dormant over the Summer.
 
 
Another way to distinguish these weeds is that Soursop grows well in heavy, fertile, well-drained soils and tends to favour areas not prone to frost.

This discusses the cultural and chemical options to remove Creeping oxalis from your lawn and turf areas.

 

 

Creeping oxalis Identification.

Creeping oxalis has three heart-shaped spotted or marked leaves and bright yellow flowers.
 
Flower: Yellow Wood Sorrel has yellow flowers with five petals that are around 15 mm in diameter. It flowers from September to April.
Height:  It grows up to 30 cm in height.
Leaf length: The leaves of Wood Sorrel are egg shaped, and 4–13 mm long. Each leaf has a distinct notch at the end of it.
Leaf width: Leaf width 11 -24 mm wide.
Reproduction: This weed reproduces by seed but spreads rapidly vegetatively.
Comments: The leaves are covered in coarse hairs.
 
Habitat: Creeping oxalis is a good indicator of soil problems. It prefers moist soil, and partial shade, can tolerate drought-prone sites, and is tolerant of a wide range of conditions.
 
 
Unlike many oxalis species, Wood Sorrel doesn’t have underground bulbs, but is able to reproduce vegetatively via a very efficient system of stolons. It allows Creeping oxalis to rapidly spread to form dense mats over turf.
 
Wood Sorrel Seedling
 

 

 

How to remove Creeping oxalis from your lawn.

Although you can attempt cultural and chemical control to remove Creeping oxalis, cultural control is very difficult.
 
 

Cultural control:

 
Cultural control of Yellow Wood Sorrel is extremely difficult as if you leave any bulbs of Creping oxalis behind in the soil it regenerates. Under close mowing it assumes a prostrate growth habit.
 
 
 
 

Chemical control:

 
There are several registered turf herbicides that control Yellow Wood Sorrel. Products that contain 2,4-D usually provide the best results.
 
Any post-emergent herbicides are best applied to Wood Sorrel in daylight hours as the leaves fold downward towards the evening, which makes it difficult to get herbicides to stick onto the foliage.