Creeping woodsorrel (Oxalis corniculata) is a low-growing perennial weed frequently found in lawns, gardens, and container pots. This plant is a significant nuisance for many homeowners because of its tenacious nature and ability to spread quickly. Successfully eliminating this weed requires a precise, multi-faceted strategy that targets its unique biology. A single control method is rarely sufficient, demanding both immediate eradication efforts and consistent long-term prevention.
Identification and Growth Habits
The foliage of creeping woodsorrel is easily recognizable by its small, trifoliate leaves, which are heart-shaped and often resemble clover. These leaves are typically green but can take on a purplish or maroon color, and they fold up at night or under intense sunlight. The plant spreads aggressively using a slender taproot system and above-ground stems, called stolons, that root at the nodes to form new plants. The primary method of dispersal is through its small, cylindrical seed capsules. When these pods mature, they rupture suddenly, explosively flinging tiny seeds up to 16 feet away, contributing significantly to its rapid spread.
Non-Chemical Control Methods
For small infestations or where chemical use is a concern, manual removal can be effective but requires diligence. When hand-pulling, it is imperative to remove the entire taproot and any rooted stolons, as leaving fragments allows the plant to regrow. Pulling the weeds when the soil is moist makes it easier to extract the full root system.
Thick mulching can suppress seed germination because Oxalis seeds require light to sprout. Applying a deep, consistent layer of organic mulch, approximately 3 inches thick, in garden beds will smother existing seedlings and prevent new ones from emerging. Household solutions like horticultural vinegar or boiling water can be used for spot treatment, but these are non-selective and will kill any surrounding desirable plants. Solarization, which involves covering an infested area with clear plastic sheeting during warm weather, can heat the soil sufficiently to kill the weed and its seed bank after several weeks.
Chemical Control Options
Herbicides are often necessary to manage large, widespread infestations of creeping woodsorrel. Successful chemical control relies on using the right product at the correct timing, differentiating between pre-emergent and post-emergent applications. Pre-emergent herbicides are applied before the seeds germinate, creating a barrier in the soil that prevents seedlings from establishing.
Post-emergent herbicides target weeds that are actively growing and are categorized as either selective or non-selective. In lawn areas, a selective broadleaf weed killer is required to kill the Oxalis without harming the turfgrass. Active ingredients effective against creeping woodsorrel typically include combinations such as triclopyr, 2,4-D, dicamba, and MCPP. Triclopyr is particularly potent against established plants.
Non-selective herbicides, like those containing glyphosate, should be reserved for landscape beds or areas where no other vegetation is present because they will kill everything they contact. Application should occur when the weed is actively growing to ensure maximum chemical uptake. It is often necessary to apply post-emergent products two or more times, spaced several weeks apart, due to the weed’s ability to regrow and continuously produce new seedlings.
Long-Term Prevention Strategies
After initial eradication, preventing the return of creeping woodsorrel focuses on cultural practices that make the environment inhospitable for the weed. Maintaining a dense, healthy lawn is one of the most effective prevention methods, as thick turf naturally outcompetes the weed for light, water, and nutrients. This involves proper fertilization, consistent watering, and setting the mower blade to a higher height.
For garden and landscape beds, maintaining the deep layer of organic mulch is paramount to preventing seed germination. The mulch suppresses the weed’s ability to establish from its explosively ejected seeds by blocking light from reaching the soil. Regularly inspecting newly purchased potted plants for any signs of the weed helps to avoid reintroducing the pest. Ensuring good soil drainage can also help reduce the moist conditions the weed favors.