How to get rid of oxalis in lawn & flower beds

Managing Oxalis Weeds: How To Get Rid Of Oxalis Weeds In The Lawn

Oxalis looks a bit like a miniature clover plant, but it bears tiny yellow flowers. It is occasionally grown as a groundcover but to most gardeners it is a tenacious and annoying weed. The persistent plant is found in many parts of the world and rises from stem fragments and tiny bulbils. Managing Oxalis weeds takes determination, bulldog-ish stubbornness and inflexible resolve. Oxalis weed control also takes time, as each and every bulbil is removed or becomes ineffective.

Oxalis Weed Facts

Buttercup oxalis, wood sorrel or sourgrass. By any name the weed is Oxalis, a tear your hair out dogged weed that can take years to remove from your garden. The low growing plant can re-establish from just a tiny stem fragment, fragile breakable rhizomes or bulbils. It produces volatile viable seed and also relies upon bits of itself being transported by animals, or us, to establish itself in almost any type of soil. Learn to get rid of Oxalis weeds with some easy steps and save yourself time and energy as well as sanity.

Oxalis is a perennial weedy groundcover, which spreads through interlocking rhizomes that are easy to break apart. Each rhizome will eventually produce tiny bulbils. The seeds are also prolific and are ejected when ripe from tiny seed pods that look like mini okra. Anywhere the stem touches the ground the plant can root, potentially producing more and more plants. It also forms a fleshy taproot and an extensive branching root system. Managing Oxalis weeds can be a huge challenge due to all the tough root system and the different methods the plant has to reproduce itself and persist.

Types of Oxalis Weeds

There are over 800 species of Oxalis. Two of the most common types of Oxalis weeds are creeping wood sorrel and Bermuda buttercup. Both of these are found across the Northern hemisphere and are persistent pests in the landscape.

  • Bermuda buttercup is most likely to grow in full sun in coastal areas.
  • Creeping wood sorrel is found in either sun or shade in moist locations.

Both spread by rhizomes and stem fragments as well as seed and bulbils. Leaves are heart shaped in both plants and held in pairs of three. One of the more terrifying Oxalis weed facts for those of us fighting this plant, is that it can bloom and set seed at any time of the year.

Managing Oxalis Weeds

The word “management” may seem like a cruel joke if you have done battle with Oxalis before. Oxalis weed control can be achieved with an herbicide. Use a formula marked for broadleaf plant control such as Dicamba, 2,4D, Clopyralid, or Tiplopyr. These are serious chemicals and you must follow all instructions and apply before the plant sets seed.

An organic option is to use liquid chelated iron. This may work in grass, which can tolerate the iron whereas the weed cannot.

The most non-toxic way is determined hand digging, but this can take several seasons to get all of the Oxalis out of your garden. Pulling is not effective, as it will leave behind fragments of rhizome, stem and bulbils, which will simply establish new plants.

Oxalis Control: How To Get Rid of Oxalis

Oxalis is an annual or perennial plant that some people find pleasant to look at because of their delicate clover-like leaves and attractive blooms. If you’re trying to keep a uniform lawn, though, Oxalis can be one of the most annoying and difficult weeds to eradicate.

Oxalis is a perpetual weedy groundcover, which spreads via interlocking underground stems (or rhizomes) that are easy to separate. Oxalis has plentiful seeds which drop when ready from little seed cases that look similar to okra. Anywhere the stem touches the ground the plant can root with the potential of creating a large number of plants.

This noxious weed usually dominates in areas of the garden planted with low ground covers. When Oxalis grows alongside ground covers it is virtually impossible to get rid of without damaging the surrounding desired grass. Managing Oxalis can be difficult because of its tough root system and the different methods the plant has to reproduce itself and persist.

If you are having a problem with Oxalis on your lawn, our DIY Oxalis treatment guide can help. The directions below were recommended by our lawn care experts and will show you how to properly eliminate Oxalis from your lawn or garden.

Identification

Oxalis, also known as wood sorrel, looks very similar to another weed called Clover, with the signature three-parted rounded leaves. Oxalis can grow between 6 to 12 inches tall and have unique shamrock-shaped leaflets in various color combinations including ones with speckles. Oxalis leaves arise from a creeping rootstock and unlike Clover, Oxalis bears flowers which vary in color from yellow to white or purple, depending on the species. At night, the leaflets fold back and droop.

Use the description and image above to help you to properly identify oxalis on your property. If you are not totally sure, contact us and send us a photo of your weed and we will identify it for you and suggest treatment options.

Inspection

Where to Inspect

Oxalis thrives in partial shade and moist, poorly-drained soil but can spring up in almost any type of soil. Oxalis grows low to the ground and even after hand-pulling and mechanical control methods, it can return from just a small left behind stem fragment, fragile breakable rhizomes or bulbils.

What to Look For

You will be able to easily notice Oxalis on your property due to its shamrock-like leaves and if mature, it’s bright flowers. It is often seen forming thick clusters of groundcover in open areas on lawns and flower beds.

Treatment

Before weed treatment, please first make sure you have on the necessary PPE (gloves, mask, glasses) prior to handling any herbicide chemicals.

If Oxalis is appearing on your lawn, apply Martin’s TopShot. TopShot is our go-to herbicide for Oxalis control because of its affordability, ease of use and the fact that it is labeled for both warm- and cool-season grasses.

Apply Topshot in the late spring when the weeds are younger and smaller. Herbicides are less effective the older and more mature the weed gets. It may need to take multiple applications to get total control of this pesky weed, especially if you have a significant outbreak.

Step 1: Mix and Apply TopShot

Martin’s TopShot comes with 2 pre-measured ampules of product that each cover 2,500 sq. ft. of area. Adding a surfactant to the TopShot mixture such as Alligare 90 can enhance the effectiveness of the Topshot. Apply Alligare 90 at a rate of 4 Teaspoons per 1 gallon of solution.

Measure the square footage of your yard and then input the appropriate amount of TopShot in a pump sprayer or hose-end sprayer by squeezing the ampule into the sprayer mixed with water. Add surfactant to the Top Shot mixture at a rate of 0.5 to 4 tsp. per gallon of the solution and agitate until well mixed.

Apply the TopShot solution to the Oxalis on a fan tip nozzle spray setting to spray a fine mist that will evenly coat the weed. Noticeable results occur in 1 to 3 weeks.

Prevention

To prevent Oxalis from popping up in lawns, make sure that you maintain thick, healthy turf. Fill up any bare spots in your lawn with sod or seed because that is where Oxalis weeds will eventually spring up. Mulch garden beds with a two- to three-inch layer of organic mulch to prevent the weed from making a home amongst your perennials or vegetables. Without sunlight, the weed seeds cannot germinate.

A pre-emergent (such as Nitrophos Barricade) may be a good preventative measure, especially if the problem is an annual occurrence. Oxalis thrives in open, fertile soil, which is why it can such a recurring problem where the soil is so favorable to growth.

Key Takeaways

  • Oxalis is a fast-growing and extremely aggressive annual weed known for its tendency to take over lawns and gardens with its low growing ground cover.
  • Our top recommendation for treating Oxalis is Martin’s TopShot due to it’s ease of use, affordability and effectiveness on both warm-season and cool-season grasses.
  • A pre-emergent herbicide like Nitrophos Barricade can be applied to your lawn before the growing season to prevent Oxalis seeds from sprouting.

Oxalis Control

Oxalis or yellow woodsorrel (Oxalis stricta) is a common cool-season perennial weed that persists almost year-around in Southeastern lawns. It grows sporadically in landscape beds among shrubs and flowers, in vegetable gardens, and is known to pop up occasionally in container plantings.

Oxalis (O. stricta) can be pulled up by hand easily when found growing intermittently in landscape beds.
LayLa Burgess, © 2017 HGIC, Clemson Extension

Oxalis has an upright form with slightly hairy stems that branch from the base of the plant at almost ground level. Erect stems give rise to an alternate leaf arrangement. Oxalis stricta leaves are green, whereas the commonly found creeping woodsorrel (O. corniculata) has green to purple leaves. Oxalis leaves are distinctly trifoliate (leaflets of three) with a heart shape similar to the leaves of clover. Often the leaves will fold along the midrib and hang down in the heat of summer, in intense light, and at night. Oxalis produces 5-petalled, yellow flowers singly or in clusters on a branched stalk. Small okra shaped fruiting capsules are formed that contain minute seeds. When mature, seeds are ejected from the capsule for a considerable distance from the parent plant. Oxalis reproduces primarily by seed but may spread by underground slender rhizomes.

Oxalis (O. corniculata) often invades container flowerpots but can be easily removed by hand pulling. Oxalis produces a 5-petalled, yellow flower followed by a seed capsule.
LayLa Burgess, © 2017 HGIC, Clemson Extension

Oxalis grows under a variety of conditions, but prefers moist fertile soils and full sun. It will tolerate shady areas. All plant parts are poisonous because of the production of soluble oxalate, but are only mildly toxic and generally causes little problem if ingested.

Cultural Control

Oxalis flowers and produces seeds heavily in the spring and summer, but can produce both all year long. Small plants can easily be handpicked or dug as they appear before they flower or form seed. Removal of all vegetative portions of the plant, including roots and rhizomes, is important. Rhizomes can be easily removed when soil is moist. Do not place the weeds with seeds in compost bins for reuse in the landscape.

A light layer of mulch in landscape beds and around flowers and shrubs will aid in preventing further germination of oxalis seeds. The seeds require light for germination, so limiting light to the seedbed with mulch will reduce the numbers of new oxalis plants.

Oxalis forms a fruiting capsule that contains multiple seeds.
LayLa Burgess, © 2017 HGIC, Clemson Extension

Maintenance of healthy, dense lawns will create less space for oxalis to invade. Lawn maintenance should adhere to fertilizer and lime recommendations obtained from soil test results combined with proper mowing height and frequency requirements. For more information on soil testing, see HGIC 1652, Soil Testing.

Chemical Control in Landscape Beds

In landscape beds, a non-selective herbicide containing glyphosate is the best choice for spot treatment of oxalis. Apply glyphosate spray to thoroughly wet the foliage of the weeds. Target oxalis seedlings and young plants (before the flowering stage) for best results. Examples of products containing glyphosate are listed in Table 1. Always read product labels for safe use around landscape ornamentals and established perennials.

Table 1. Examples of Products Containing Glyphosate in Homeowner Sizes.

Active Ingredient Product Name
glyphosate Roundup Original Concentrate
Roundup Pro Herbicide
Martin’s Eraser Systemic Weed & Grass Killer
Quick Kill Grass & Weed Killer
Bonide Kleenup Weed & Grass Killer 41% Super Concentrate
Hi-Yield Super Concentrate
Maxide Super Concentrate 41% Weed & Grass Killer
Super Concentrate Killzall Weed & Grass Killer
Tiger Brand Quick Kill Concentrate
Gordon’s Groundwork Concentrate 50% Super Weed & Grass Killer
Zep Enforcer Weed Defeat III
Eliminator Weed & Grass Killer Super Concentrate
Monterey Remuda Full Strength 41% Glyphosate
Southern States Grass & Weed Killer Concentrate II
Total Kill Pro Weed & Grass Killer Herbicide
Ace Concentrate Weed & Grass Killer

Chemical Control in Lawns

For small numbers of oxalis plants scattered throughout the lawn, a spot treatment with a recommended post-emergent herbicide may provide adequate control. For larger oxalis infestations in the lawn, pre-emergent and post-emergent herbicides may be necessary. Pre-emergent herbicides prevent seed growth, whereas post-emergent herbicides are applied to foliage of the weeds once they emerge. Post-emergent herbicides are often more effective at killing smaller weeds rather than older, mature ones.

Pre-emergent and post-emergent herbicides for oxalis (yellow woodsorrel) control in South Carolina lawns are listed in Tables 2 and 3. Always read the product label for mixing rate for weed control on each turfgrass species and for safe use of the product. Pre-emergent herbicides need to be applied at the proper time of the year, may require one or more subsequent applications, and need to be watered in appropriately. When using a post-emergent herbicide, spray to just wet the foliage of the weeds. For safe use on lawns, spray herbicides when temperatures are below 90 °F. Avoid pesticide drift by spraying on non-windy days. Irrigate the lawn the day before application to reduce drought stress to lawns and to promote active growth of the weed for better herbicide uptake.

Table 2. Pre-emergent Herbicides for Oxalis Control in Home Lawns.

Turfgrass Active Ingredients Examples of Brands & Products
Bahiagrass
Bermudagrass
Centipedegrass
St. Augustinegrass
Zoysiagrass
Tall Fescue
benefin Pennington Crabgrass Preventer
oryzalin Southern Ag Surflan A.S.
benefin + oryzalin XL2G
Green Light Amaze Grass & Weed Preventer
benefin + trifluralin Anderson Turf Products Crabgrass Preventer with 2% Team Herbicide (partial control)
Hi-Yield Crabgrass Control (partial control)
pendimethalin Scotts Halts Crabgrass & Grassy Weed Preventer
dithiopyr Bonide Crabgrass & Weed Preventer for Lawns & Ornamental Beds
Hi Yield Turf & Ornamental Weed & Grass Stopper Containing Dimension
StaGreen CrabEx Crabgrass Preventer
isoxaben Ferti-lome Broadleaf Weed Control with Gallery
prodiamine Helena Pro-Mate Barricade & Fertilizer 0-0-7
Howard Johnson Crabgrass Control with Prodiamine & 0-0-7
Lebanon Pro Fertilizer (0-0-7) with Prodiamine
Lesco Barricade Plus Fertilizer 0-0-7
Lesco Stonewall Plus Fertilizer (0-0-7)
Pro-Mate Barricade Plus Fertilizer (0-0-7)
Scotts Halts Pro 0-0-7 & Halts Pro
Notes: These pre-emergent herbicides should only be applied to well-established turfgrass lawns.
Typically, the optimum time for lawn fertilizer applications and pre-emergent herbicide applications do not coincide. However, the small amount of potash in the 0-0-7 blends is not a problem, & may be useful on sandy soils with fall applications to improve cold weather hardiness of the lawn.

Table 3. Post-emergent Herbicides for Oxalis Control in Home Lawns.

Turfgrass Active Ingredients Examples of Brands & Products Effectiveness
Centipedegrass
St. Augustinegrass
atrazine Hi-Yield Atrazine Weed Killer
Image for St. Augustinegrass & Centipedegrass
with Atrazine
Southern AG Atrazine St. Augustine Weed Killer
Spectracide Weed Stop for Lawns Concentrate for St. Augustine & Centipede Lawns
Fair to Good Control
Bahiagrass
Bermudagrass
Centipedegrass
St. Augustinegrass
Zoysiagrass
Tall Fescue
2, 4-D + dicamba + mecoprop (MCPP) Ferti-lome Weed Out Lawn Weed Killer with
Trimec
Southern Ag Lawn Weed Killer with Trimec
Conc.
Good Control
Bermudagrass1
Zoysiagrass
Centipede
Tall Fescue
sulfentrazone +
quinclorac
Image Kills Crabgrass Concentrate Good Control
Zoysiagrass2
Tall Fescue
triclopyr Ortho Weed B Gon Chickweed, Clover & Oxalis
Killer
Fair to Good Control
Tall Fescue triclopyr Hi-Yield Triclopyr Ester
Monterey Turflon Ester
Fair to Good Control
Bahiagrass
Bermudagrass
Zoysiagrass
Tall Fescue
MCPA + dicamba + triclopyr Monterey Spurge Power Concentrate
Bonide Chickweed, Clover & Oxalis Killer Concentrate
Good Control
1For use on common bermudagrass. Intermediate safety on hybrid bermudagrass.
2Use low rate on zoysiagrass.
Effectiveness Rating:
Poor – P = <70% control
Fair – F = 70-79% control with repeat applications
Good – G = 80-90% control with one application at high rate or repeat application
Excellent – E = >90% control with one application

Integrated Pest Management

Fact Sheets > Fruit > Small fruit > Strawberries

Strawberry Weeds: Yellow Wood Sorrel

Identification

There are several species of yellow wood sorrel. All are similar in appearance. Leaves are a bright, light green and are divided in three heart-shaped parts. Although they are lighter green in color, leaves are otherwise quite similar to those of clover. Leaves are often folded downward, giving them the appearance of a closed umbrella. Flowers are a bright golden yellow, with five petals. Size and growth habit of the plant vary considerably. Plants generally grow upright, but have weak stems and may creep along the ground. Entire plants are generally no more than eight inches tall. Yellow wood sorrel is most often found growing right in and among strawberry plants.

Characteristics:

Yellow wood sorrel is an extremely common weed in strawberry plantings. Plants are able to grow in and among strawberry plants, thriving in the shade cast by the strawberry leaves. This makes them difficult to kill with hand weeding, hoeing, and herbicides. Yellow wood sorrel is low-growing and shallow-rooted, and probably does not compete with strawberries for light, but at extremely high densities it may compete with the crop for water and nutrients. In addition, dense growth of this weed can make it hard for pickers to find fruit and may block air flow, making plants more susceptible to fungal diseases. Although this weed is fairly attractive, large quantities of it would probably be considered unsightly in a pick-your-own field.

In Massachusetts, the most frequently found species of yellow wood sorrel is common yellow wood sorrel, Oxalis stricta. This species of yellow wood sorrel is a perennial. Common yellow wood sorrel is a simple perennial, meaning that it spreads only by seed. Plants pulled up will often have a thickened pinkish root, which enables it to survive the winter. Common yellow wood sorrel does not have runners. Seeds are contained in an upright pod, which starts out green, then matures to a light green or brown color. When the pod is dry, it will split open along seams, forcefully throwing its small, red-brown seeds from the plant. This enables yellow wood sorrel to colonize new areas of the field. Yellow wood sorrel spreads extremely quickly. Within a few years, a small infestation can fill an entire field.

Yellow wood sorrel is edible. The green seed pods, leaves, and stems can be eaten in salads. Plants have a pleasant lemony taste and will quench thirst on hot summer days. Yellow wood sorrel contains oxalic acid, which can be toxic if consumed in large quantities.

Management:

Chemical: Germination of seeds of yellow wood sorrel takes place over a long period of time through the year. This makes control with pre emergence herbicides difficult. Sinbar is the only pre emergence herbicide currently registered for use in ESTABLISHED strawberry fields that provides some control of yellow wood sorrel. At registered rates, however, control is usually less than adequate. Splitting the annual use rate of Sinbar into a renovation and late fall application is recommended. The late fall application should be made after plants become dormant. Some post emergence control can be obtained with 2, 4-D in established plantings. Plants will be controlled only if they are small and not hidden under strawberry foliage. The application should be made prior to mulching, over dormant strawberry plants. Strawberry plants are dormant when leaves have developed a reddish color and plants become flattened in appearance. A 2, 4-D application prior to renovation is usually not effective, since plants have already produced and dispersed their seeds by early summer. Consult your Cooperative Extension center for the most up-to-date chemical information.

Nonchemical: Growers who do not yet have yellow wood sorrel should consider scouting for it on a yearly basis. Scouting can serve as an early warning signal for this and other troublesome strawberry weeds. Removing this weed by hand when it first appears in a strawberry bed can prevent a small problem from becoming a big one. Similarly, growers with multiple plantings may want to consider cleaning equipment when moving from infested fields to fields free of this weed. Small numbers of this weed can probably be eradicated from plantings through frequent and vigilant hand weeding. Rotating to crops other than strawberries for several years should also make a big dent in the population of yellow wood sorrel seeds in the soil.

Integrating chemical and nonchemical control: Combining chemical and nonchemical approaches may be the most economical way to attack yellow wood sorrel. Partial control can be obtained with the herbicides described above. Control of plants, which escape these herbicides, can be obtained with nonchemical measures such as cultivation, mulching, hoeing, and hand weeding. Rotating to other crops as often and for as long as possible should also be of great help in reducing problems caused by yellow wood sorrel and many other strawberry weeds.

By: M.J. Else and A.R. Bonanno, University of Massachusetts Extension

Updated by: Mary Concklin, UConn IPM. 2012

The information in this document is for educational purposes only. The recommendations contained are based on the best available knowledge at the time of publication. Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended. The Cooperative Extension System does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available. The University of Connecticut, Cooperative Extension System, College of Agriculture and Natural Resources is an equal opportunity program provider and employer.

How to Manage Pests

Pests in Gardens and Landscapes

Creeping Woodsorrel and Bermuda Buttercup

Revised 6/10

In this Guideline:

  • Identification and life cycle
  • Impact
  • Management
  • About Pest Notes
  • Publication
  • Glossary

Creeping woodsorrel.

A variant of creeping woodsorrel, O. corniculata variety atropurpurea, has purple leaves.

Under intense sunlight, creeping woodsorrel plants often fold their leaves downward.

Bermuda buttercup.

Bermuda buttercup bulbs.

Creeping woodsorrel, Oxalis corniculata, is a weed species that occurs in many parts of the world. In California it usually grows below the 2,500-foot elevation level and frequently appears in lawns, flower beds, gardens, nurseries, and greenhouses.

A related species, Bermuda buttercup, O. pes-caprae, is a South African native that grows in California’s coastal gardens and fields as well as inland landscaped areas. Bermuda buttercup, also called Buttercup oxalis, has been cultivated as an ornamental, and although you’ll occasionally find it in lawns, more often it is a problem in flowerbeds, groundcovers, and shrub areas in home landscapes or in commercial, field-grown flowers. In recent years it has been encroaching in natural areas and hillside plantings along California’s coast.

The genus name Oxalis is derived from the Greek word meaning “sour,” referring to the sour-tasting oxalic acid present throughout the plants. If livestock ingest large quantities, they can suffer from oxalate poisoning.

IDENTIFICATION AND LIFE CYCLE

Creeping Woodsorrel

A perennial plant that lives for several seasons, creeping woodsorrel grows in a prostrate manner (low and creeping) and forms roots and stems where nodes contact the soil. It grows in both full sun and shade if the area receives adequate moisture.

The leaves are comprised of 3 heart-shaped leaflets attached to the tip of a long stem. Leaves are green to purple and often close and fold downward in intense light and at night. If creeping woodsorrel plants are stressed due to drought or intense heat, the leaves sometimes turn reddish and wilt.

Creeping woodsorrel can bloom almost any time during the year, although spring is a time of heavy flowering and seed formation. The flowers have 5 small, yellow petals about 1/8- to 1/3-inch long that are borne singly in small clusters of 2 to 5 flowers on the ends of short, slender stalks.

Seedpods are erect, hairy, cylindrical capsules with a pointed tip about 1/3 to 1 inch long and resemble miniature okra. Seeds are oval, flat, rough, reddish brown sometimes with gray spots, and about 1/25 inch long. There are about 10 to 50 seeds per pod, with a potential for more than 5,000 seeds per plant. When seedpods mature, they rupture, and seeds are forcefully expelled, landing up to 10 feet from the plant. Because seeds are rough, they can stick to machinery, plastic pots, irrigation tubing, and clothing.

Seeds require light for germination. Optimum seed germination occurs between 60° and 80°F, although it can occur at lower temperatures. Seeds can germinate any time of year in California, but most plant establishment takes place in fall. It isn’t known how long seeds remain viable in the soil. Moist, hot conditions inhibit seed germination; for example, 4 hours of moist heat at 97°F decreases germination by 96%, while 8 hours stops it altogether.

Seedlings have 2 round leaves, and the first true leaves are a replica of the mature, heart-shaped leaflets. Creeping woodsorrel grows rapidly, forming a fleshy taproot and an extensive root system that expands outward. Seedlings begin flowering in about 4 weeks. Extremely cold or hot temperatures reduce growth but won’t kill the plants. If you pull creeping woodsorrel from the ground, the taproot or stolons often break off and remain in the soil, allowing the plant to regrow. Pieces of roots and prostrate stems can develop into new plants when conditions are favorable.

Bermuda Buttercup (Buttercup Oxalis)

Bermuda buttercup is a perennial that grows in full sun in cool coastal areas, but inland it grows primarily in semishaded sites. It grows upright and is larger and showier than creeping woodsorrel.

It develops from bulbs that sprout and grow in the fall. The plant forms a single, short, vertical stem that is mostly underground. Leaves form a loose basal rosette on the soil surface. The leaves are comprised of 3 heart-shaped leaflets and are larger and more succulent than those of creeping woodsorrel; they often are spotted with purple dots.

Small, whitish bulblets develop on the stem at the base of the rosette of leaves, and new bulbs form underground. A plant forms about a dozen small bulbs per year, each less than 1 inch long. Bermuda buttercup also can produce a lateral stem (runner) that forms a new, aboveground plant.

Flowers appear in late winter or early spring. The flowers are bright yellow, 3/4 to 1 1/2 inches in diameter, and are borne on top of a leafless stalk rising 6 to 12 inches tall. Viable seed never has been documented in California, and rarely has it been seen anywhere else in world. Foliage dies and the bulbs become dormant when temperatures rise in late spring and summer. Bermuda buttercup reproduces vegetatively by bulbs and spreads when plants are divided or soil containing the bulbs is moved to uninfested areas.

IMPACT

Creeping woodsorrel is a major weed in turf, ornamental plantings, and nurseries. Infested container stock can contaminate uninfested landscapes. As seedpods mature and expel seeds, creeping woodsorrel spreads from container to container, from flower bed to flower bed, or across ornamental plantings. Creeping woodsorrel can establish rapidly in semishaded areas of new or established grass lawns or low-growing perennial ground covers. It spreads during mowing and other cultural operations.

Once established, it is very competitive, because it grows year-round. This makes it particularly troublesome in warm season turf species such as bermudagrass or perennial groundcovers that have a dormancy period.

Bermuda buttercup used to be grown as an ornamental, but once planted it would spread throughout a garden, compete with other plants, and become very difficult to control. It still is plentiful in many landscapes. Although it can spread into the edges of turfgrass, mowing reduces its invasiveness, so it rarely is a problem in lawns. It is a major problem in field-grown flowers and in the home landscape, especially in groundcovers.

Bermuda buttercup was first noted in California in the San Francisco Bay region and has since spread throughout most coastal counties, the coastal range, and into the Central Valley. In the last 10 years, this plant has invaded native coastal dunes and natural areas along the coast, leading to the demise of native plants. It is a troublesome weed that is more competitive than is assumed from its general appearance.

Due to its extensive occurrence in yards and gardens, Bermuda buttercup has the potential to rapidly spread via the production of bulbs and the movement of contaminated soils into adjacent natural areas. Because it is practically impossible to eradicate infested soils of this weed, take care to prevent Bermuda buttercup from invading wildlands.

MANAGEMENT

In many garden situations creeping woodsorrel and Bermuda buttercup can be managed with physical control methods such as handweeding. In other cases, herbicides can be integrated into the management program; see Tables 1 and 2. The effectiveness of control method depends on which weed is present and where the weeds are growing.

Creeping woodsorrel

The two primary methods for managing creeping woodsorrel are removing established plants and controlling germinating seeds. You can control established plants with handweeding, hand cultivation with hoes and weeding tools, and postemergent herbicides. Try to control plants before they flower and set seed. Infested sites require constant vigilance and continuous weed removal.

Control seedlings by preventing seed germination and/or seedling emergence with preemergent herbicides and/or mulches along with continual handweeding. Burying seeds or covering them with mulch to block their exposure to light prevents germination and is an effective way to control seedlings in planting beds; it isn’t a feasible method for lawns. Preemergent herbicides can be used to prevent seedling emergence in most sites where creeping woodsorrel grows. Both pre- and postemergent herbicide selection is dependent upon the site of infestation.

Bermuda buttercup (Buttercup oxalis)

Bermuda buttercup grows mostly in ornamental beds, where control is difficult and complicated by the presence of ornamental plants. Removing the top of the plant by cultivating or cutting it off won’t kill the bulb. Don’t move soil from an infested site to one that is free of the weed. Handweeding is used extensively to reduce infestations, but because it is exceedingly difficult to remove all of the bulbs, new plants usually appear. Bermuda buttercup isn’t a common problem in lawns.

Creeping Woodsorrel in Turfgrass

Mowing, fertilizing, or irrigating to control creeping woodsorrel isn’t effective; the more vigorous the turfgrass, the more vigorous the creeping woodsorrel. Creeping woodsorrel survives and sets seed even when mowed as close as 1/4 inch. After using a lawn mower where creeping woodsorrel grows, wash or air spray the machine to remove all seeds and clippings before mowing weed-free turf.

Postemergent herbicides

All postemergent herbicide applications are more effective when air temperatures are favorable for plant growth and not too hot or too cold. Be sure to follow label instructions and apply the herbicide uniformly over the entire lawn. Some of these products are active in the soil, as indicated on the label, so extra care is needed around shrub and tree roots growing in a lawn. Adding a surfactant (sometimes referred to as an herbicide helper) to the spray mixture, if indicated on the label, increases herbicide coverage and penetration by the leaf.

Cool-season turfgrass (bent­grass, Kentucky bluegrass, tall fescue, and ryegrass)

Triclopyr and fluroxypyr are two postemergent broadleaf herbicides that are extremely effective in controlling seedling and established creeping woodsorrel plants in cool-season turfgrass lawns. Triclopyr is more readily available to the homeowner than fluroxypyr. These herbicides sometimes are sold in combination with other broadleaf herbicides.

Table 1. Herbicides for Controlling Creeping Woodsorrel.

Herbicide Commercial name Available to home gardeners?
Preemergents—apply before weeds emerge—for landscape plants and turf
dithiopyr Dimension yes
isoxaben Gallery, Portrait Broadleaf Weed Preventer yes
oryzalin1 Surflan, Weed Impede yes
oryzalin1 + benefin XL 2G, Amaze Grass & Weed Preventer 2, PrimeraOne OB–2G yes
pendimethalin Halts, Pendulum, PreM yes
prodiamine Barricade no
Postemergents—apply to young weeds—for use in turf only
2,4-D/2,4-DP/MCPP Weed Whacker yes
2,4-D/MCPP/dicamba Lawn Weed Killer, Trimec, Weed-B-Gon Lawn Weed Killer, Wipe-Out Broadleaf Weed Killer2, several others yes
2,4-D/MCPP/dicamba/carfentrazone Speed Zone yes
fluroxypyr Spotlight no
triclopyr2 Clover & Oxalis Killer for Lawns, Turflon Ester, Weed-B-Gon Chickweed yes
triclopyr/MCPA/dicamba Spurge Power, Weed-B-Gon Max Killer for Lawns yes
Nonselective postemergents—will kill turf or landscape plants
glufosinate Finale yes
glyphosate RoundUp yes
1 Not safe for all turgrass species. Check the label.
2 Not for use on bermudagrass and kikuugrass.

The broadleaf weed herbicides 2,4-D, 2,4-DP, carfentrazone, dicamba, MCPA, and MCPP (mecoprop) sometimes are sold singly but more commonly are sold in 2-, 3-, and 4-way combinations of varying strengths. These materials are available at garden and landscape supply centers. Some combinations are specifically formulated for creeping woodsorrel and provide effective control. Alone, 2,4-D has limited effect on creeping woodsorrel. Often one application of triclopyr is adequate for control, but a follow-up application 3 to 6 weeks later might be necessary for complete control, and a second application is almost always needed for the other products discussed above.

Warm-season turfgrass (bermudagrass, buffalograss, kikuyugrass, St. Augustinegrass, and zoysiagrass)

Triclopyr is harmful to bermudagrass and kikuygrass, so it isn’t labeled for use in warm-season turfgrass lawns as a stand-alone herbicide. However, it has been formulated in a lower concentration and combined with other broadleaf herbicides (e.g. dicamba and MCPA) and is effective on creeping woodsorrel. Fluroxypyr, a similar chemistry to triclopyr, is safer to use in warm-season lawns and is very effective on creeping woodsorrel. Postemergent broadleaf herbicide combinations also are formulated for use in some warm-season turfgrasses. Several of these specifically target creeping woodsorrel and provide effective control.

Table 2. Herbicides for Bermuda Buttercup.1

Herbicide Commercial Name Available to home gardeners?
fluroxypyr Spotlight No Selectively kills broadleaves. Not for use around broadleaf ornamentals or vegetables.
glufosinate Finale Yes Nonselective. Will injure turf and ornamentals.
glyphosate Round-Up Yes Nonselective. Will injure turf and ornamentals.
triclopyr Clover and Oxalis Killer for Lawns, Turflon Ester, Weed-B-Gon Chickweed Yes Selectively kills broadleaves. Not for use around broadleaf ornamentals or vegetables or warm-season turf.
Preemergent herbicides for cool and warm-season turfgrasses

Once established plants are under control, a preemergent application of dithiopyr, isoxaben, pendimethalin, or prodiamine will effectively prevent oxalis emergence. Oryzalin and oryzalin combined with benefin provide some preemergence activity on creeping woodsorrel. Oryzalin can’t be used in all turfgrass species, so check the label for restrictions and carefully follow the directions for use. These materials are available at garden and landscape supply centers.

Preemergent herbicides can be applied any time of the year, and 3 applications per year might be necessary to reduce a heavy infestation and prevent creeping woodsorrel from establishing in lawns. Application timings of early fall, midwinter, and late spring are suggested.

Landscape Plantings

Before planting in an infested area of either creeping woodsorrel or Bermuda buttercup, soil solarization—a method for killing weeds using a clear, plastic tarp and the sun’s heat—can be used to reduce seed and bulb populations. To achieve the most effective results, perform solarization for a minimum of 4 consecutive weeks during June, July, or August. For more information, see Soil Solarization for Gardens and Landscapes.

Control is difficult in areas with shrubs, herbaceous perennials, or groundcovers, particularly if established creeping woodsorrel plants aren’t under control in other areas of the landscape. Total control of established woodsorrel and its seedlings is necessary in turfgrass, groundcovers, and bedding plants and around shrubs to prevent the weed from reestablishing. In severely infested areas it might be easier to start over and relandscape the site or parts of the landscape, salvaging as many ornamental plants as feasible or desirable. Prior to planting, use soil solarization or cultivate and sprinkle with water to germinate the seeds and then destroy the seedlings to reduce seed populations in the soil. You might need to repeat this process several times.

Carefully handweed oxalis around established plants to remove as much of the stem sections as possible, since they easily break. Several weedings usually are necessary to remove old plants, since new ones will grow from stem segments that remain in the soil. To reduce the chance of further infestation, remove the plants from the site to eliminate their seed, then apply a mulch, preemergent herbicide, or both to control seedlings.

Two types of mulching materials are effective—geotextile fabrics (landscape fabrics) and organic mulches used alone or on top of geotextile fabrics. When using organic mulches, cover the soil with 2 to 3 inches of mulch. If any light reaches the soil, seeds can germinate, or plant parts can regrow. If seeds drop on the soil between mulch pieces, they usually will germinate and grow; therefore, it is important to use a mulch size that is small enough to fill in most spaces on top of the soil but not so fine (e.g. sawdust) that the seeds will germinate on the mulch.

If you are using preemergent herbicides to control creeping woodsorrel, two applications about 8 weeks apart might be necessary to control all of the seedlings. Apply preemergents in the early fall, since this is when most seeds germinate.

Dithiopyr, isoxaben, oryzalin, pendimethalin, and prodiamine are available for commercial and homeowner use. Read herbicide labels carefully to determine if applications are safe around bedding plants. Be aware these herbicides also will inhibit germination of any ornamental seeds that are in the site. If using preemergents and mulches, first apply the herbicide, then lay the fabric or spread a thick layer of mulch. No selective postemergent herbicides are available to control creeping woodsorrel in ornamental plantings after the weed has emerged.

The best control method for this pernicious weed is prevention. If new infestations are spotted and controlled early, it is possible to eradicate small populations. Large populations are difficult to control and will require multiple years of diligent control efforts.

Small infestations can be controlled by repeated manual removal of the entire plant. Repeated pulling of the tops will deplete the bulb’s carbohydrate reserves, but these efforts will take years to be successful. Repeated mowing also will eventually deplete the bulb. Cut Bermuda buttercup before it flowers and forms new bulbs. Repeated cutting or cultivation is necessary to reduce plant numbers. The soil from which plants are removed should be carefully examined or sifted to remove bulbs and bulblets, an extremely time- and labor-intensive process. Before planting in an infested area, use soil solarization to further reduce Bermuda buttercup populations.

Several postemergent herbicides including triclopyr and fluroxypyr (selective for broadleaf plants) and glyphosate and glufosinate (nonselective) effectively kill the top growth of this weed but are harmful to most ornamentals, so be careful these herbicides don’t drift onto desirable plants. These herbicides don’t kill the bulbs, and regrowth from bulbs should be expected.

Researchers around the world are investigating approaches for controlling Bermuda buttercup. Some suggest covering infestations with stiff cardboard, then covering the cardboard with a thick layer of organic mulch to kill the plants and weaken the bulbs, making them less capable of competing with desirable plants. Keep the mulch on the infestation until the mulch and cardboard have rotted, then plant competitive ornamentals into the soil-mulch mixture.

Container-grown Ornamentals

Bermuda buttercup typically isn’t a problem in container-grown ornamentals; however, creeping woodsorrel is a major problem. When planting new containers, use soil that is free of creeping woodsorrel seeds or Bermuda buttercup bulbs. When purchasing container plants from nurseries, avoid those with either species of Oxalis growing in the pots. If you find mature plants, carefully pull them out to remove all of the roots and/or bulbs. Fabric or organic mulches help prevent seed germination but have little effect on bulb germination.

WARNING ON THE USE OF PESTICIDES

DiTomaso, J. M., and E. A. Healy. 2007. Weeds of California and Other Western States. Oakland: Univ. Calif. Agric. Nat. Res. Publ. 3488.

Kingsbury, J. M. 1964. Poisonous Plants of the United States and Canada. Newark: Prentice Hall.

Sigg, J. 2003. Oxalis pes-caprae. Cal EPPC News. 11(1):7–8.

Tu, Mandy. Oxalis pes-caprae L. The Nature Conservancy Global Invasive Species Team. Accessed June 18, 2010.

Whitson, T. D., R. Parker, B. E. Nelson, R. D. Lee, D. W. Cudney, L. C. Burrill, and S. A. Dewey. 2006. Weeds of the West. 9th ed. Darby: Diane Pub Co.

PUBLICATION INFORMATION

Pest Notes: Creeping Woodsorrel and Bermuda Buttercup

UC ANR Publication 7444

Produced by UC Statewide IPM Program, University of California, Davis, CA 95616

Editor: M. Fayard

Technical Editor: M. L. Flint

Produced by University of California Statewide IPM Program

PDF: To display a PDF document, you may need to use a PDF reader.

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Control Creeping Oxalis – Treatment

What does Creeping Oxalis look like and how to control it?

Another member of the large family of oxalis species, this form differs from the others in that it does not produce underground bulbs and spreads rapidly by means of stolons that simply root into the surrounding soil. It spreads quickly not only by stolons, but also by explosive seed dispersal enabling it to colonise lawns, garden beds and all potted plants.

Recognising creeping oxalis weed

Creeping oxalis has small, trifoliate leaves similar to many other members of the oxalis tribe, yet is distinguished by its capacity to quickly run along the surface of the soil and produce roots at each leaf node. Flowers are usually small and yellow in colour.

How to control creeping oxalis in lawns and gardens

Control of creeping oxalis can be difficult as each and every piece of stem left behind will survive to re-grow a new plant. Careful, physical removal of plants from pots is a better option that using chemical sprays in and around special plants, yet applications of registered herbicides in amongst lawns at the beginning of the growing season of spring is often the best approach.

Control creeping oxalis by spraying with Searles Lawn Perfect.
Note: ???If you have creeping oxalis in Buffalo (except ST varieties), Paspalum or rye grass lawns, Searles Buffalo Master is a safe treatment to use.
Click to view our Searles Lawn Weed Control chart for the right lawn weed killer to use for your lawn type.

Effectively Killing Oxalis Weeds

Oxalis is a Difficult Weed to Kill

Oxalis can be a very difficult weed to kill in most lawn types. It is highly resistant to weak herbicide products, such as Weed and Feed types of weed killers. With prior knowledge of the difficulty in killing Oxalis, and knowledge and planning in weed control practices, the job can be done very effectively and with the least amount of resistance from the tough Oxalis weed.

Buy a proper herbicide

Oxalis weeds in lawns will require a proper concentrated herbicide in order to kill the weed completely. Most of these herbicides will be marketed as Broadleaf herbicides, or may even be sold as herbicides for Bindi weeds. The good news is that these herbicides will kill many other lawn weed types as well.

WARNING: Buffalo and Kikuyu lawn owners will need to ensure they are buying a variety of Broadleaf herbicide witch has been specifically formulated for their grass types. Applying the wrong herbicide can severely damage or kill these lawn types.

A concentrated Broadleaf herbicide will cost between $10 and 15, and is readily available in many shops which sell garden products.

A 3-4 litre spraying bottle with a wand applicator will also be required, these are also quite cheap at around $10 to 15.

Mixing and applying the herbicide

Always follow manufacturer’s instructions exactly.

Do not apply any lawn herbicides 1 week before or after lawn mowing. Do not apply herbicides to a wet lawn or when rain or lawn watering is expected within 3 days after application.

Do not apply herbicides to lawns which are under stress such as drought, or on hot weather days.

The herbicide is mixed inside the spraying bottle and diluted with water as per manufacturer’s directions.

Affected areas of Oxalis are then sprayed with the herbicide. There is no need to do other lawn areas unless there are other weed types. Broadleaf herbicides are the most versatile of all herbicides and will kill many different weed types.

Multiple Oxalis herbicide treatments

Because Oxalis is so difficult to kill, the weed may require several treatments, expect and plan for this in advance.

After the first herbicide treatment is completed, leave the lawn for 2 weeks to wait for results.

After 2 weeks, carefully walk around the lawn looking for Oxalis which hasn’t yet died.

Repeat the Oxalis herbicide treatment to any remaining remnants of the weed.

Leave the lawn for another 2 weeks, and repeat the process again if necessary.

If any Oxalis is still remaining 2 weeks after the third treatment, it is time to give the lawn a rest from the herbicide. Give the lawn an application of quality lawn fertiliser and ensure a good watering, and leave the lawn for 4-6 weeks before applying herbicide again.

Other Oxalis herbicide considerations

Keep children and pets off the sprayed area for a week after treatment. Check specific manufacturer’s instructions for exact times to stay off a sprayed lawn. If necessary, section off the lawn and spray in 2 stages.

Only mix enough herbicide which is suitable for treatment, and thoroughly wash out spray bottles after treatment. Old herbicides can become concentrated or lose their effectiveness, so always mix a fresh batch prior to use. Products left in spray bottles can also clog up the spraying mechanisms.

How to fight back against Creeping Oxalis

What a Creep!

Creeping Oxalis has small light green heart shaped leaves, very similar in appearance to clover.

How to fight back against Creeping Oxalis (Procumbent Yellow Sorrel)

Scientific name: Oxalis corniculata

Creeping Oxalis has small light green heart shaped leaves, very similar in appearance to clover. (Oxalis, have heart shaped leaves while clover has oval shaped leaves.) The flowers are small, about 3-4mm in diameter and bright yellow in colour containing five petals. Creeping Oxalis, as its name suggests, quickly runs along the surface of the soil and produces roots from the leaf as it goes and creeps under and through your lawn. When seed pods mature they dry out and explode, causing the seed to spread. It is a very invasive and nasty weed, so it is important to take action against it as soon as possible.

Treatment

Creeping Oxalis is difficult to remove as crowns break off leaving roots for re-growth. You can hand remove small plants or dig out sections where you need to if they aren’t particularly large. If there is a substantial spread of Creeping Oxalis through your lawn, you will get better results by spraying your lawn with a selective herbicide.

A selective herbicide such as Lawn Solutions Australia All Purpose Weed Control will help to eradicate these weeds in all lawn types including kikuyu and couch and are safe to use on most varieties of buffalo except the ST varieties.

Lawn Solutions Australia carry a wide range of weed and pest control products for buffalo and other lawn varieties. Remember to always follow manufacturer’s instructions on the pack.

The best way to keep on top of creeping oxalis is through prevention. By maintaining your lawn regularly with fertilising and watering, your lawn will be healthier and less susceptible to the infiltration of weeds like Creeping Oxalis. Raising your lawn mower height is particularly important in winter and will help you to avoid scalping of your grass, which also makes your lawn more susceptible to weed invasion. When weeds do occur, it is important to take action early and get on top of them before they get out of control and are more difficult to manage.

Check out the Lawn Solutions Australia lawn care page for more helpful tips and advice here.

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Getting Rid of Oxalis

Question:

How do I get rid of Oxalis – the green way?

Hardiness Zone: 6a

Liz from Hawkes Bay, New Zealand

Answer:

Liz,

Fortunately, oxalis (also known as common woodsorrel) is not that difficult to eliminate. I applaud your search for a “green” solution. All too often gardeners look for the quick fix. Using homemade weed killers, like vinegar or salt, are certainly more benign than their synthetic counterparts, but they still change the soil’s chemistry in a significant way. They also kill beneficial microorganisms and insects, without which, ironically, the chances for weed, pest and disease problems are greatly increased. Hoeing and hand pulling are probably the most effective methods of control, but if I were you, I would try a combination of strategies just to see what works best.

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Oxalis is commonly found in stony or rocky areas and in soils with a more acidic pH. It reproduces by seeds (which are thrown long distances by the pod) and also sometimes from nodes (bulblets) on the stem. Digging out oxalis is certainly the most labor intensive method of control (you’ll have to dig down at least 6 inches), but it’s also the greenest method and it will leave your soil healthiest in the long run. You might also try singeing some of the plants with a small propane torch and whacking a few of the plants down to ground level, which will eventually weaken the bulbs. Finally, if you have large areas inhabited by oxalis, you might find covering the areas with black plastic or thick layers of newspaper or mulch works well. The keys to green weed control are cultivation and mulching.

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Good Luck!
Ellen

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