Yellow Wood Sorrel (Oxalis stricta), commonly called Oxalis or sour grass, is a vigorous weed. It is a summer annual — sometimes perennial — that thrives in fertile, warm and moist soils and likes shade.
- White Clover
- Black Medic
- Summer annual and sometimes perennial.
- Reproduces and spreads by seed.
- Pale green to maroon heart-shaped leaves.
- Leaves fold up in full sun.
- Yellow flowers with five petals.
- Likes moist, warm, fertile soils.
- Can be very aggressive where grass is weak or thin.
The leaves, flowers and unripe fruits are edible, with a mild lemon-sour flavor – that’s where it gets the name sour grass. Edible gardeners use it as a salad green or add it to soups, sauces, or as a seasoning. It is rich in vitamin C and will quench thirst on hot summer days. Kind of nice to chew on when weeding.
Oxalis can be easily confused with clover when not in flower. It is differentiated by its small yellow flowers, heart-shaped leaflets, and lime-green to purple color.
A very common weed in lawns, greenhouses, landscape beds and container plants.
Yellow Wood sorrel has an interesting and effective way to spread seeds. The pods build up pressure as they dry and then burst, sending the seed flying several feet. You can make the seed pods pop by lightly touching them.
Oxalis will take advantage of bare and thin areas in your lawn, quickly filling them in.
Hand Weeding – Hand weeding is very effective. It pulls easily and will not re-sprout from roots left behind. Removing the plants before they go to seed reduces the population.
Chemical Control – Pre-emergence herbicides are the most useful, they prevent seed germination – the way oxalis spreads.
Many post-emergent herbicides are not effective. Timing and the use of a spreader/sticker are important. Yellow wood sorrel has a very waxy leaf and stems, water beads and rolls off. A spreader/sticker will break down the waxy layer, allowing the herbicide to penetrate into the leaf and then do its job.
Spot spraying young plants works well.
Oxalis Weed ID
Stems – The stems are thin, sparsely hairy and able to root at the nodes.
Leaves – Leaves are a bright, light green to maroon color. They are compounded with three heart-shaped leaflets and arranged alternately along the stem on long petioles.
Each leaflet is creased down the mid-rib. The leaves fold at this crease during the night and open in the morning. They also fold when under stress or in full sun.
Flowers – Tiny, bright yellow flowers with five petals that are 4 to 9 mm long. It starts blooming in mid-spring – producing flowers into the fall.
Roots – Long, slender rhizomes occur with a fibrous root system.