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Lawn and Turfgrass Weeds: Yellow Woodsorrel, Oxalis stricta L.

Yellow woodsorrel, also referred to as oxalis, sourgrass, and other names, is a weed of home lawns, parks, golf courses, and athletic fields.

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Updated:

May 17, 2023

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Figure 1. Yellow woodsorrel plant growing near a sidewalk in a Pennsylvania lawn. Photo: Peter Landschoot, Penn State

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This species is found in high and low maintenance turf, in sunny and shaded areas, and in moist and dry soils. Yellow woodsorrel tends to grow in an upright manner and exists as individual plants or small patches in turf. It is frequently found near flower beds and along sidewalks and is most noticeable when flowering during summer.

Life Cycle

Yellow woodsorrel is a member of the Oxalidaceae family and is classified as both an annual and perennial. Plants have taproots and rhizomes that produce new plants at nodes. This species produces yellow flowers, seed capsules, and seeds from late spring to early fall. Seeds germinate during spring and give rise to new plants.

Identification

Yellow woodsorrel plants grow close to the ground as first, then produce upright, branching green stems with leaves and flowers. Light green or reddish-green leaves with long petioles are arranged alternately on stems and have three heart-shaped leaflets. Individual leaflets are smooth and approximately ¼ to ½ inch in diameter. Leaves droop and fold at night, then expand in daylight. Groups of small yellow flowers, ¼ to ½ inch in diameter, arise from leaf axils. Individual flowers have five yellow petals that are rounded and often notched at tips. Flowers are eventually replaced by elongated cylindrical seed capsules that range from 1/3 to 3/4 inch in length. When mature, capsules split and eject seeds into the air, often landing several feet from the capsule.

Figure 2. Leaves of yellow woodsorrel showing heart-shaped leaflets. Photo: Peter Landschoot, Penn State

Figure 3. Yellow woodsorrel flowers with five yellow petals. Photo: Peter Landschoot, Penn State

Figure 4. Seed capsules of yellow woodsorrel. Photo: Peter Landschoot, Penn State

Figure 5. Rhizome (left) and taproot (right) of yellow woodsorrel. Photos: Peter Landschoot, Penn State

Management and Control

Infestations of yellow woodsorrel can be reduced by improving turf density through fertilization, regular mowing, and use of turfgrasses well-adapted to site conditions. This weed can be controlled with various postemergence herbicides, particularly those containing combinations of 2,4-D, dicamba, MCPP, and/or fluroxypyr; as well as herbicides containing triclopyr. Some preemergence herbicides will control yellow woodsorrel from seed but have no effect on plants emerging from rhizomes.

Table 1. Some preemergence herbicide products labeled for control of yellow woodsorrel from seed.
Active ingredients	Product name(s)*
dithiopyr	Dimension 2EW; Dithiopyr 40WSB
pendimethalin	Pendulum 3.3 EC, Lesco Pre-M
prodiamine	Barricade 65WG, Barricade 4FL, Prodiamine 4L, Prodiamine 65WG
isoxaben	Gallery 75DF

*Follow label precautionary statements, restrictions, and directions regarding tolerant turfgrass species, rates, and timing of applications.

Table 2. Some postemergence herbicide products labeled for control of yellow woodsorrel.
Active ingredients	Product name(s)*
2,4-D and 2,4-DP	Patron 170 (ester formulation)
2,4-D, 2,4-DP, and dicamba	Super Trimec (ester formulation)
2,4-D, clopyralid, and dicamba	Millennium Ultra 2**
2,4-D, fluroxypyr, and dicamba	Escalade 2 Herbicide, Escalade
2,4-D, fluroxypyr, triclopyr, and flumioxazin	Sure Power (ester formulation)
2,4-D, MCPP, dicamba	Trimec Classic, 3-D Herbicide, Primera Triplet SF
2,4-D, MCPP, dicamba, and carfentrazone-ethyl	Speedzone
2,4-D, MCPP, dicamba, and sulfentrazone	Surge
2,4-D, quinclorac, and dicamba	Quincept, 2DQ Herbicide, Triad QC Select, Triad SFZ Select
2,4-D, quinclorac, dicamba, and sulfentrazone	Q4 Plus
2,4-D and triclopyr	Chaser 2 Amine, Turflon II Amine
2,4-D and triclopyr	Chaser Turf Herbicide (ester formulation)
2,4-D, fluroxypyr, and triclopyr	Momentum FX2
2,4-D, fluroxypyr, triclopyr, and sulfentrazone	Momentum 4-Score
2,4-D, triclopyr, dicamba, and pyraflufen-ethyl	4-Speed XT (ester formulation)
2,4-D, triclopyr, dicamba, and sulfentrazone	Foundation
carfentrazone-ethyl and quinclorac	SquareOne
fluroxypyr	Vista XRT
MCPA, fluroxypyr, and dicamba	Change Up
MCPA, fluroxypyr, and triclopyr	Battleship III
MCPA, MCPP, and dicamba	Trimec Encore, Tri-Power Selective Herbicide
MCPA, MCPP, dicamba, and carfentrazone-ethyl	Powerzone (ester formulation)
MCPA, triclopyr, and dicamba	Lesco Three-Way Ester II, Cool Power (ester formulation)
MCPA, triclopyr, and dicamba	Eliminate, Horsepower
Mesotrione	Tenacity
triclopyr	Triclopyr 4 (ester formulation); Turflon Ester Ultra
triclopyr and clopyralid	2-D Herbicide, Confront
triclopyr and fluroxypyr	Tailspin