Purple clover weed is a common plant often found in lawns and gardens, frequently mistaken for true clover. It can be a persistent nuisance for gardeners. Understanding its characteristics is important for effective management.
Identifying Purple Clover Weed
Purple clover weed, primarily Oxalis species like Oxalis triangularis (purple leaf shamrock) and Oxalis corniculata (creeping woodsorrel), has distinct features. Its leaves are trifoliate, meaning they have three leaflets, similar to true clover. However, Oxalis leaves are typically heart-shaped or triangular, differentiating them from the more rounded leaflets of true clover (Trifolium species). Some varieties, like Oxalis triangularis, have deep maroon or purple foliage, while others, like Oxalis corniculata, can have green to reddish-purple leaves.
The plant’s stems can be upright or creeping, often rooting where they touch the ground. Small, five-petaled flowers typically appear on slender stalks. While some Oxalis species produce yellow flowers, others may have pinkish-purple, white, or pale pink blooms. Oxalis also exhibits nyctinastic behavior, where leaflets fold downward at night or during stress, reopening with daylight.
Why Purple Clover is Considered a Weed
Purple clover is considered undesirable due to its invasive nature and rapid spread. It quickly outcompetes desirable turfgrass and garden plants for nutrients and water. Its aggressive growth allows it to form dense mats, potentially smothering smaller plants.
The plant reproduces efficiently through prolific seed production and the development of rhizomes, stolons, or bulbils. Oxalis seeds are problematic as they are often ejected explosively from mature seed pods, scattering several feet away. This makes manual removal challenging, as disturbing the plant can inadvertently spread more seeds. Its resilience and ability to regrow from small root fragments or bulbils make it difficult to eradicate.
Effective Control and Removal Strategies
Managing purple clover weed requires a combination of methods. For small infestations, manual removal is viable; however, ensure all root portions and associated bulbils are completely removed from moist soil to prevent regrowth. Hand-pulling is most effective when plants are young and before they produce seeds. Dispose of pulled weeds, especially those with seeds, in the trash rather than compost to avoid further spread.
Cultural practices play a significant role in prevention and control. Maintaining a healthy, dense lawn through proper fertilization, watering, and mowing at the correct height can help turfgrass outcompete weeds and reduce opportunities for purple clover to establish. In garden beds, applying a 2-3 inch layer of mulch can suppress seed germination by blocking light.
For larger or persistent infestations, chemical control may be considered. Pre-emergent herbicides can prevent seeds from germinating, often in late winter/early spring or fall. Post-emergent herbicides, including selective broadleaf weed killers, can target existing plants. Non-selective herbicides containing glyphosate can be used for spot treatments in landscape beds, but care must be taken to avoid desirable plants. Always read and follow product label instructions for safe and effective application, considering factors like temperature and wind conditions.