Creeping Oxalis Weed

No gardener likes weeds but some tax even the most patient of green thumbs. Oxalis corniculata, also known as creeping oxalis weed, is one that drives many gardeners batty. A perennial plant, it’s almost impossible to kill in one battle. It survives for several seasons, so even when you think you have it under control, up it pops up the following spring. Creeping oxalis especially thrives in full sun but will do well in shade if the soil is moist. Creeping oxalis is hardy in U.S. Department of Agriculture hardiness zones 5 and above.

Creeping oxalis does just that – it creeps across the soil putting down roots wherever a node comes into contact with soil. It bears heart-shaped leaflets on long stems that fold when the sun goes down. Spring is its favorite season, blooming profusely and forming more than 5,000 seeds per plant. When the seed pod ripens and pops, seeds can be expelled to a distance up to 10 feet. They also stick to everything, including pets and clothing, thereby spreading around the garden and beyond.

Creeping oxalis is a pain in the garden. It sprouts in container stock in nurseries and then is transferred to the home landscape. Whether it is a flower bed or a lawn, creeping woodsorrel will, if not stopped, take over. In fact, when turfgrasses go dormant it rapidly takes over the space, blocking the sun and moisture. Because the seeds so readily germinate, the weed easily crowds out the emerging turf during spring green-up.

Pulling creeping oxalis weed is the recommended first step of a two-pronged approach to control. Small infestations can be pulled by hand, otherwise use a hoe to remove the weeds and do so before they set seed. Use a thick layer of mulch to prevent seeds from germinating. This may be a problem if the infestation occurs in a lawn. In this case, use a pre-emergent herbicide, such as pendamethalin, in spring. Load the herbicide into a broadcast or rotary spreader. Use 2 pounds of the herbicide per 1,000 square feet of lawn and apply 1 inch of water after the application.

Creeping oxalis seeds need light to germinate. A 4- to 5-inch layer of mulch in the garden beds should prevent light from reaching the seeds, thus preventing germination. Once the seeds germinate, they send down a long taproot and then extend horizontal roots. Since the plant flowers at 4 weeks, it’s important to keep an eye on the garden and hand-pull the weed as soon as it emerges. Try to remove the entire taproot or the weed will regrow.