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Oxalis Guide

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How to Identify Oxalis Weeds

How to Identify Oxalis or Wood Sorrel

Oxalis flowering weeds
Oxalis, commonly known as wood sorrel, is a low-growing annual weed that often resembles clover or shamrock varieties. Certain types of oxalis, like yellow wood sorrel (Oxalis stricta), are invasive and prevalent across much of the eastern United States.

Yellow wood sorrel is particularly aggressive, thriving in nutrient-poor soils and outcompeting other plants in the area. Use this guide to identify oxalis weeds, and then explore our tips on controlling oxalis in your lawn.

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Flowering Oxalis or Wood Sorrel Weeds

Most oxalis weeds share several defining features. Use the list below to help identify oxalis in your yard:

  • Low-growing, short annual weed that blooms in summer
  • Weak, branching stems growing outward from the base
  • Produces yellow, white, or pink flowers with five petals
  • Leaves are comprised of three heart-shaped, smooth-edged leaflets, each about 1/2 inch wide
  • Features a taproot with rhizomes to spread new plants
  • Produces an abundance of seeds, with nearly 100% germination rates
  • Seed capsules burst open, ejecting seeds up to 16 feet away

Oxalis vs. Other Weeds
Common oxalis or wood sorrel (Oxalis acetocella) has heart-shaped leaves, which can be mistaken for other weeds. However, they can be distinguished by their:

  • Heart-shaped leaves compared to the circular leaves of clover (Trifolium repens)
  • Heart-shaped leaves compared to the oval-shaped leaves of black medic (Medicago lupulina)

Refer to the comparison image below to note the differences when inspecting your property for weeds.

Larger Oxalis Varieties
Some varieties of oxalis, such as Oxalis triangularis (false shamrock), feature dark purple, fan-shaped leaves and are often grown as ornamental or indoor potted plants. This guide focuses on controlling oxalis varieties that grow as weeds in lawns and landscapes.

Now that you can identify oxalis, discover how to inspect for it in the next section of our guide. Click the right arrow below to continue.

How to Inspect for Oxalis in Your Lawn

Oxalis flowering weeds
After reviewing our Oxalis Identification Guide, you should now be equipped to spot this weed if it’s present on your property. Next, let’s discuss the conditions where oxalis is most likely to grow and how to locate it effectively.

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When Are You Likely to Find Oxalis?

Oxalis typically flowers during the summer months but can remain in bloom year-round under favorable conditions. During warm weather, the colorful flowers of wood sorrel emerge, and the plants produce abundant seeds, allowing the weed to spread quickly. In addition to seed dispersal, oxalis can expand through its rhizome-based root system, making it a persistent invader.

Where Does Oxalis Thrive?

Oxalis weeds, also known as wood sorrels, thrive in a variety of environments, especially in the southeastern United States. These weeds are common in:

  • Landscaped areas among ornamentals, shrubs, and flowers
  • Vegetable gardens
  • Lawns and turfgrass

Although oxalis can adapt to various conditions, it thrives best in locations with:

  • Full sunlight
  • Well-moisturized soil
  • Adequate soil fertility

By knowing where to look and understanding these growth preferences, you can proactively inspect for oxalis on your property.

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Concerned about oxalis weeds invading your lawn? Check out our How to Prevent Oxalis guide for detailed information on when and how to apply these oxalis weed preventers to keep your lawn weed-free.

How to Eliminate Oxalis Weeds

Which Products Are Best for Controlling Oxalis?

A patch of yellow oxalis flowers on a grassy area

Oxalis, also known as wood sorrel, can be managed effectively with selective broadleaf herbicides specifically labeled for this type of weed. Use this treatment guide to learn the best practices for applying these products and removing oxalis from your lawn.

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Controlling Oxalis on Lawns with Selective Post-Emergent Herbicides

To treat oxalis in grassy areas, select a post-emergent herbicide labeled for oxalis or wood sorrel. Since oxalis tends to bloom during the summer, monitor your lawn for the characteristic five-petaled flowers to identify and treat infestations.

Key Herbicide Ingredients:

  • Look for active ingredients like atrazine or a combination of dicamba and 2,4-D.
  • Ensure the product is compatible with your specific turf type. Some herbicides are only suitable for certain grasses.

Persistent Weeds:

Oxalis often leaves seed pods underground, enabling new stalks to sprout even after treatment. Repeated applications may be necessary to fully eradicate the weed. Seedlings commonly germinate from late winter to early spring, with growth visible by summer. However, some seeds can sprout year-round under favorable conditions.

Managing Oxalis in Landscaped Areas

If oxalis is growing among ornamentals or in landscaped areas, use a non-selective herbicide containing glyphosate. Treat weeds early, ideally while they are still seedlings and before flowering.

Precautions for Non-Selective Herbicides:

  • These products will damage surrounding plants, making them unsuitable for use on lawns.
  • Target only the oxalis to minimize harm to desirable vegetation.

Oxalis spreads not only by seeds but also through rhizomes. Even small root fragments can grow into new plants. Non-selective herbicides are the most effective way to combat oxalis in landscaped beds.

Preventing Future Oxalis Growth with Pre-Emergents

To stop oxalis seeds in the soil from germinating, apply a pre-emergent herbicide in the fall before the first frost. Products with active ingredients like Prodiamine and Isoxaben are effective at preventing oxalis seed germination.

For ongoing prevention and a weed-free lawn, consider combining pre-emergent applications with regular lawn maintenance practices.

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Discover how to stop oxalis from returning in the final section of our guide. Click the right arrow below to learn effective strategies for preventing future oxalis growth on your property.

How to Prevent Oxalis Weeds from Taking Over

Maintain a Lawn Maintenance Routine
Keeping your lawn and landscaped areas healthy is essential to preventing invasive weeds like oxalis from stealing water and nutrients. A well-maintained lawn is your first line of defense against oxalis and other weeds.

Explore our recommended lawn maintenance schedules to help your lawn stay healthy and resilient against unwanted growth like wood sorrel or oxalis.

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Step1 Follow a Proper Fertilization Schedule

How to Apply Granule Lawn Fertilizer
Fertilizing your lawn properly can prevent weeds like oxalis from establishing themselves. A soil test can help you determine what nutrients your lawn is missing. Based on the results, choose a fertilizer tailored to your lawn’s needs to strengthen its defenses.

Some fertilizers include weed-killing properties, known as "weed & feed" products, which can help prepare your lawn for future seasons while preventing weed growth.

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Step2 Implement Good Cultural Practices

Healthy Lawn Practices
Maintaining the right soil moisture and following cultivation best practices are critical to stopping oxalis from taking over.

  • Water Wisely: Follow your local extension office’s recommendations for how much water your lawn needs. Water deeply to nourish the roots effectively.
  • Mow Properly: Mow at the right height, removing no more than the top one-third of the grass blades. This encourages stronger growth and suppresses weeds by cutting off seed-producing flowers.
  • Use Mulch: Apply a three-inch layer of mulch to landscape beds. This blocks sunlight needed for oxalis seed germination, effectively preventing weed growth.
  • Aerate Annually: Aerate your lawn once a year to break up compacted soil, allowing deeper grass root growth, which strengthens the lawn's natural defense against weeds like oxalis.

Step3 Apply a Pre-Emergent Herbicide

Prevent Oxalis Before It Starts
Pre-emergent herbicides labeled for oxalis or wood sorrel control can stop these weeds from germinating. Timing is key:

  • Fall Application: Apply pre-emergents before the season’s first frost to maximize protection. Use local weather resources to determine the best time.
  • Spring Application: After the ground thaws, apply pre-emergent herbicides before soil temperatures reach 50–55°F, as this is when weeds start to germinate.

For areas already infested with oxalis, dig up the taproots of visible plants to prevent regrowth. Be vigilant about treating any new growth with a selective post-emergent herbicide to tackle rhizomes or fragments left behind.

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