What Is Yellow Wood Sorrel? Identification and Removal

Yellow wood sorrel (Oxalis stricta) is an annual or perennial weed in the wood sorrel family (Oxalidaceae). It looks similar to clover, except that the foliage is curved or folded at the center of each leaf. The leaves fold at night and open again during the day. Its small 1/2-inch five-petalled flowers are bright yellow. It grows 6 to 15 inches tall and spreads by rhizomes to form dense mats.

The plant, which is native to North America and Eurasia, is considered a weed throughout the United
States. It is commonly found in lawns. In mild climates, it grows year-round.

Learn how to identify wood sorrel and promptly remove it from your yard before it spreads.

Common Names	Yellow woodsorrel, common yellow oxalis, upright yellow-sorrel, lemon clover, sourgrass, sheep weed
Botanical Name	Oxalis stricta
Plant Type	Perennial, annual, herbaceous
Mature Size	6-12 in. tall
Soil Type	Moist, well-drained
Bloom Time	Spring, summer, fall
Flower Color	Yellow
Hardiness Zones	5-11 (USDA)
Native Area	North America, Europe, Asia
Toxicity	Toxic to dogs and cats

What Is Yellow Wood Sorrel?

In the United States, yellow wood sorrel grows in open woods, prairies, stream banks, gardens, and poor soils. It is reported as a weed in most of the contiguous United States as well as in parts of Canada.

Warning

Yellow wood sorrel is reported as invasive in Kentucky by the Kentucky Exotic Pest Plant Council.

The plant is toxic to dogs, cats, and horses.

This weed prolifically spreads through horizontal stems (runners) and seeds that take root where it touches the soil. The seed pod distributes the mature seeds as far as 10 feet. Seeds also get stuck on garden tools, clothing, pets, and other wildlife, transferring to other areas. The seeds set from late summer through fall. The roots are complex, far-reaching, and challenging to pull. Tugging at the stems of wood sorrel breaks the top portion away, leaving the root network and giving it a chance to resprout.

Yellow Wood Sorrel Identification

Like clover, the leaves of yellow wood sorrel radiate from a single point like fingers from a palm in threes. The stems, branches, and leaf stalks have fine hairs on them. The plant forms in thick clumps.

Yellow wood sorrel foliage has a bright green color. The small yellow five-petaled flowers bloom from mid-spring to fall. The flower is about 1/2 inch in diameter. The plant doesn't usually grow taller than 20 inches. The plant produces small, green seed pods that look like okra; they're about 1/2 to 3/4 inches long.

How to Remove Yellow Wood Sorrel Weed

Yellow wood sorrel often plagues lawns and garden beds. There are two ways to get rid of it—manually and with herbicides.

Manual Removal

Digging wood sorrel up by hand requires thoroughness and time because if any of the tiny roots are left behind, the weed will resprout. Manual removal often involves digging up nearby plants to sift through the soil and remove roots of yellow wood sorrel that have encroached into neighboring plants.

Herbicides

Post-emergent herbicides work best on this plant. The broad-spectrum herbicide glyphosate (sold under the brand name Roundup) will kill the entire plant, roots, and all; it is the most effective chemical solution. Other narrow-spectrum weed killers won't affect wood sorrel.

Warning

Glyphosate kills all plants indiscriminately, so apply it with utmost caution. Some gardeners brush the weed-killer by hand onto the leaves of the weed. If you spray, use a small spray bottle to target on the weeds you want to kill. Wait for a calm, windless day so the chemical won't drift onto other plants.

If the wood sorrel weed is growing in cool-season turfgrass, such as bentgrass, Kentucky bluegrass, ryegrass, or tall fescue, treat the lawn with a post-emergent herbicide that contains the ingredient triclopyr. Be careful with herbicides because they may have other ingredients.

When treating weeds in warm-season turfgrass such as St. Augustine grass, Buffalo grass, or Bermuda grass, use a post-emergent herbicide containing the active ingredient fluroxypyr.

Post-emergent herbicides for yellow wood sorrel control can be applied at any time during the growing season when temperatures don't exceed 85°F. Application is possible even in the fall when the weeds are preparing for winter. However, late spring is the best time to apply the herbicide, as the weed is still small and much easier to kill. It may take several applications to control yellow wood sorrel.

Make sure to follow the instructions on the label when using a herbicide.

How to Prevent Yellow Wood Sorrel Weed

There are three main ways to prevent yellow wood sorrel:

• Do not let the plant set seed. Because yellow wood sorrel blooms on and off, it also produces seeds at different times. Dig out the plants as soon as you see them. Get as much of the root as possible.
• Maintain thick, healthy turf. Yellow wood sorrel weed thrives in open, fertile soil, which can be a problemin lawns and garden beds, where the soil is favorable to growth. Overseed any bare spots in your lawn or lay down sod because that is where wood sorrel weed will find an opportunity to grow.
• Mulch garden beds. A two- to three-inch layer of organic mulch prevents the weed from making a home amongst your perennials or vegetables. Without sunlight, the weed seeds cannot germinate.

None of these methods guarantee that yellow wood sorrel won't reappear in your yard t since seeds travel via wind, birds, or other animals.

Wood Sorrel vs. Clover

Yellow wood sorrel is easily mistaken for red or white clover. One distinguishing feature is that yellow wood sorrel has heart-shaped leaves while red and white clover leaves are oval-shaped. Also, the flowers of white clover are white, and red clover flowers are a deep pink color.

Wood sorrel is also often confused with shamrocks, another plant in the clover family commonly grown as a houseplant. Another plant that is often mistaken for yellow wood sorrel isblack medic, a cool-season summer annual.It has three leaflets and small yellow flowers.

From: thespruce