The plant frequently searched as “Purple Clover Weed” is Oxalis, or wood sorrel, which often features reddish-purple foliage. This common misidentification occurs because its leaves mimic the three-leaflet structure of true clover (Trifolium). Understanding the precise identity of this invasive plant is key to effective management, as its unique reproductive biology demands targeted removal strategies. This guide provides clear identification markers and detailed control methods.
Identifying the Purple Clover Weed
The plant most often identified as “purple clover weed” is Oxalis corniculata, commonly known as creeping wood sorrel, which is distinguished by its green to purple-tinged leaves. While true clover (Trifolium) has leaves composed of three rounded or oval-shaped leaflets, Oxalis features three distinct leaflets that are characteristically heart-shaped. These leaflets often fold down the midrib at night, in intense heat, or during cloudy weather.
Creeping wood sorrel is a low-growing plant that spreads by rooting stems that hug the ground, but its upright relative, yellow wood sorrel (Oxalis stricta), is also common. Both species produce small, five-petaled flowers, typically yellow, which bloom from late spring through summer. The presence of purple or reddish-hued leaves is a strong indicator of the invasive creeping wood sorrel.
How This Weed Spreads and Persists
The difficulty in eradicating Oxalis stems from its efficient and multi-faceted reproductive system, which includes both underground storage structures and aggressive seed dispersal. Creeping wood sorrel spreads laterally through above-ground stems, called stolons, which root at the nodes to form new plants. Some perennial Oxalis species develop clusters of small, fleshy underground bulbs known as bulbils. These bulbils are easily detached and left behind when the main plant is pulled, leading to rapid re-infestation.
The most notable mechanism for wide distribution is the plant’s unique seed capsule, shaped like a tiny okra pod. When these capsules mature, they rupture explosively upon being disturbed, scattering minute seeds up to 16 feet from the parent plant. Seeds can also be spread by water, on mowing equipment, or by animals. This combination of stolons, bulbils, and explosive seed dispersal makes the plant exceptionally persistent and challenging to control.
Comprehensive Control and Removal Methods
Effective control of Oxalis requires a combination of manual, chemical, and cultural strategies due to its persistent nature. Manual removal is most effective for small or newly established infestations, but it must be performed with precision. The entire root system, including any underground bulbils, must be carefully dug out when the soil is moist to minimize the chance of leaving fragments behind. Disposing of the uprooted plants in the trash, not the compost pile, is crucial to prevent the spread of seeds and bulbils.
For larger outbreaks, chemical control often becomes necessary, utilizing both pre-emergent and post-emergent herbicides. Pre-emergent herbicides, applied in late winter or early spring before germination, create a chemical barrier in the soil to prevent new seeds from sprouting. For already emerged plants, a selective post-emergent herbicide formulated for broadleaf weeds is applied directly to the foliage. These applications are most effective when the plants are young and actively growing, before they begin to flower and set seed.
Long-term prevention relies on cultural practices that create an environment unfavorable for weed establishment. Maintaining a thick, dense lawn is the best defense, as healthy turf outcompetes the weed by limiting sunlight and available space. This involves proper lawn care, including adequate fertilization and mowing at the appropriate height. In garden beds, applying a thick layer of organic mulch, two to three inches deep, suppresses seed germination by blocking the light they require to sprout.