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.
| 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.
| 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 |
*Follow label precautionary statements, restrictions, and directions regarding tolerant turfgrass species, rates, and timing of applications.
**Clopyralid-containing products should not be used on residential lawns but can be used for treating weeds in non-residential turf.
References
Hilty, J. 2017. Illinois wildflowers. Yellow wood sorrel.
Uva, R.H., J.C. Neal, and J.M. DiThomaso. 1997. Weeds of the northeast. Cornell Univ. Press. 397 pp.
