yellow wood sorrrell also known as Creeping Oxalis

low growing weed Creeping oxalis Oxalis corniculata

distribution of creeping oxalis, or yellow wood sorrel in Australia

Creeping oxalis (Oxalis corniculata).

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Creeping oxalis (Oxalis corniculata) is an annual or sometime perennial herb. It is also known as Yellow Wood Sorrel or Wood Sorrel, and is often mistaken for White Clover but has some distinct differences.

Reasons Why Creeping Oxalis is a Problem in Turfgrass.

Once it establishes Oxalis corniculata rapidly spreads.
It forms dense mats which choke out existing turf grass.
Creeping Oxalis competes with turf for soil nutrients.
Oxalis corniculata is difficult to eradicate due to its bulbous root system, and the fact it spreads by stolons.
The leaves of Creeping oxalis are difficult to wet which affects herbicide uptake.
Aesthetically the bright yellow flowers can be an issue.

The stolons of Creeping oxalis creep above the ground, and are up to 60 mm long. The slightly hairy stems are light green to red purple, and slightly thickened. Trifoliate leaves alternate along these stems, and it’s these leaves that cause confusion with White Clover.

The are two easy ways to tell White Clover and Creeping oxalis apart:

The flower of Creeping oxalis is yellow. White Clover has pink or white flowers.
White Clover has a distinct white marking on its leaves. Creeping oxalis does not have this.

Another weed it is often mistaken for is Soursob or Soursop (Oxalis pes-caprae). The main differences between these are:

Soursob does not have creeping above ground stolons and reproduces via bulbs.
Wood Sorrel does not have these underground bulbs.
The flowers of Creeping oxalis are much smaller than those of Soursob.
Soursop grows well in heavy, fertile, well-drained soils and tends to favour areas not prone to frost. Creeping oxalis is more frost tolerant.
Soursob flowers mainly in the Winter and goes dormant over the Summer.

The leaves of Creeping oxalis have a lemony flavor and you can use these to make a Vitamin C rich tea. However, it contains large amounts of oxalic acid (hence its name) which can block calcium absorption in the body.

This discusses the cultural and chemical options to remove Creeping oxalis (Oxalis corniculata) from your lawn and turf areas.

How to Identify Creeping oxalis.

Creeping oxalis has three heart-shaped leaves and bright yellow flowers.

Photosynthetic pathway: C3 weed.

Flower: Yellow Wood Sorrel has yellow flowers with five petals that are 4 to 5 mm in diameter. It flowers from September to April.

Height: Creeping oxalis grows to a height of 10 to 35 cm.

Leaf length: The leaves of Wood Sorrel have an egg shape, and are 4 to 13 mm long. Each leaf has a distinct notch at the end of it.

Leaf width: Leaf width is 11 to 24 mm.

Reproduction: Creeping oxalis reproduces by seed, and also spreads vegetatively. The seeds travel up to 5 metres out of seed pods, and then are transported on shoes, fur and machinery. The seeds germinate very quickly.

Comments: The leaves of Creeping oxalis have a cover of coarse hairs.

Habitat: Creeping oxalis is a good indicator of soil problems. It prefers moist soil, and partial shade, and is tolerant of drought. More weed information is in our Weed ID Chart.

How to Remove Creeping oxalis from your lawn.

Although you can attempt cultural and chemical control to remove Creeping oxalis or Yellow Wood Sorrel, cultural control is very difficult. That’s why an integrated approach is the best, but be aware that once this weed establishes it is difficult to control. Autumn is an ideal time carry out control of this perennial weed.

Cultural Control of Creeping oxalis.

Both hand removal and mowing are not effective to control Yellow Wood Sorrel.

The deep tap root means if you hand weed, and leave any plant material behind in the soil it regrows.
Under close mowing it takes on a prostrate growth habit.

Chemical Control of Creeping oxalis.

There are several turf herbicides for the control Yellow Wood Sorrel. As Creeping oxalis is difficult to wet, we suggest you use Optispread 1000 to ensure good herbicide contact with the target weed.

For large Creeping oxalis infestations, a combination of pre and post-emergent herbicides is the most effective approach to take.

Pre-emergents prevent seed growth, whereas you apply post-emergents to weeds once they emerge. Post-emergents are often more effective to kill small weeds rather than older, mature ones.

Pre-Emergent Herbicides for Creeping Oxalis.

BASF Freehand Herbicide
Echelon Duo.
Indaziflam. Interestingly, this gave excellent pre and post emergent control of Creeping oxalis in 2020 work.

Post Emergent Control of Creeping Oxalis.

Products that contain 2,4-D tend to give the best results vs Creeping Oxalis. The Sulfonylurea herbicides like Recondo and Duke, are also very effective against this weed.

Apply post-emergents to Wood Sorrel in daylight hours as the leaves fold downward towards the evening. This is called nyctinasty, and you can also see this in Gazania and Morning Glory. When the leaves of Creeping oxalis fold it makes it difficult for herbicides to stick to the foliage.

Dicamba. Do not use on Buffalo Grass.
Pylex. Do not use on warm season turf. Apply to actively growing Wood Sorrel. In some cases a single hit of Pylex may not give complete control. In this case you may need a follow up 21 to 28 days later.
Warhead Trio. Safe on Buffalo.
Stature Herbicide. Not for use in the home garden.
Recondo Herbicide. Do not use on Buffalo Grass.
Weed Blast MA. Safe on Buffalo.
Contra M. Do not use on Buffalo Turf
Duke Herbicide. Safe on most Buffalo varieties.

Table of Post Emergent Herbicides for Creeping Oxalis.

Product	Active	Chemical Group	Rate/Ha	Comments
Casper	Prosulfuron + Dicamba	2 and 4	800g-1Kg	Apply from Autumn to Spring. Use high rates in cool months or if high weed pressure. Control takes 4 to 6 weeks. Use an NIS at a rate of 0.25 to 0.5% v/v.
Contra M.	Dicamba + MCPA	4	6.5 L	Apply in 250-400L water. DO NOT use on Buffalo grass. After use do not mow for 2 days before or after application or fertilize within two weeks.
Dicamba	Dicamba	4	1.2L + 3.2L of 2,4-D Amine 625g/L	Use a minimum of 1000L/Ha water. Do not spray on Buffalo or Bent Grass.
Duke	Iodosulfuron	2	100g	Always use an NIS or Overtake Oil. Use in 200-500 L/ha water.
Pylex	Topramezone	27	0.375 mL/ 100 m2 in 4-6 L water + 0.5% MSO	Make two applications 21-28 days apart. You may see bleaching of Bentgrass after 7-14 days. Do not water for 24 hrs post application.
Recondo	Trifloxysulfuron	2	225g	Use an NIS at 0.25% v/v (1000 g ai/L), 0.42% v/v (600 g ai/L) or Overtake Oil at 1%v/v. Ensure uniform placement onto leaves & into crowns. Water volume is 400 to 800 L/ha. You may need a repeat application in 4 to 6 weeks. Allow at least 6 weeks before overseeding. You may see discolouration on Qld Blue and Zoysia.
Warhead	MCPA + Clopyralid + Diflufenican	4 + 12	5 L	You may see discolouration on kikuyu, carpet grass and Queensland blue. Avoid overlapping. Use an NIS.
Weed Blast MA.	Bromoxynil + MCPA	6 + 4	3-6 L	Apply in a minimum of 500L/Ha water. DO NOT mow for 2 days after treatment.