Oxalis, a diverse genus of over 550 species in the wood-sorrel family, is found worldwide. Recognized for its clover-like foliage and delicate, five-petaled flowers, its name comes from the Greek “oxalis” meaning “acid,” referring to the tart taste of many species. This group includes both ornamental varieties and common garden weeds.
Understanding Oxalis
Oxalis species typically feature leaves divided into three to ten or more leaflets, usually obovate and notched at the tip. Most varieties have three leaflets, and their flowers display a range of colors including white, pink, red, yellow, and multi-colored forms. Some species, like Oxalis triangularis with its dark purple leaves, are grown for their striking foliage.
Many Oxalis plants possess underground structures like bulbs, rhizomes, or corms, allowing them to store energy and spread. These structures contribute to their growth habits, whether cultivated intentionally or appearing as opportunistic weeds. Their leaves also fold back and droop at night, reopening with daylight.
Growing Oxalis as a Houseplant
Cultivating ornamental Oxalis indoors adds color and unique foliage. These plants thrive in bright, indirect light; too much direct sun can scorch leaves. An east-facing window is ideal, providing gentle morning sunlight. Insufficient light may lead to leggy growth.
Oxalis prefers well-draining soil, often a mix of indoor potting soil with added sand or grit. Water when the top inch of soil feels dry, keeping it consistently moist but not waterlogged to prevent root rot. Most Oxalis houseplants prefer temperatures between 60 to 75 degrees Fahrenheit, aligning with typical indoor environments. While humidity is generally moderate, tropical species may benefit from additional humidity.
Many Oxalis species undergo a natural dormancy period, often in late summer or early autumn, where foliage may die back. During this time, reduce or cease watering until new growth emerges, typically in late winter or early spring. This dormancy cycle allows the plant to rest and rejuvenate. Propagation is straightforward, usually by dividing rhizomes or bulbs during dormancy and replanting in fresh soil.
Controlling Oxalis as a Garden Weed
Persistent Oxalis garden weeds include yellow wood sorrel (Oxalis stricta) and creeping wood sorrel (Oxalis corniculata). These weedy forms often have heart-shaped leaves, distinguishable by their growth habit and smaller, more delicate flowers. They spread through underground stems and produce numerous seeds that can be explosively dispersed up to 16 feet from the parent plant.
Manual removal is effective but requires diligent effort to extract the entire plant, including its underground bulbs or rhizomes. Pulling only top growth is insufficient, as the plant regrows from remaining structures. Repeated weeding, especially when soil is moist, depletes the plant’s energy reserves. Applying a 2-3 inch layer of organic mulch also helps suppress seed germination, as Oxalis seeds often require light to sprout.
For larger infestations or when manual methods are impractical, chemical control can be a last resort. Non-selective herbicides with glyphosate are effective for spot treatments in garden beds, but use extreme caution to avoid contact with desirable plants. For lawns, specific pre-emergent or post-emergent herbicides are available; timing is crucial for success. Always adhere strictly to product instructions for safe and effective use.
Important Considerations
Oxalis plants contain oxalic acid. While small amounts are harmless, large quantities ingested by humans or pets can cause issues. Oxalic acid can interfere with calcium metabolism and, in severe cases, may lead to kidney stone formation or kidney damage due to calcium oxalate crystallization.
Symptoms of significant ingestion include gastrointestinal upset such as nausea, vomiting, and diarrhea. Exercise caution, especially around children and pets, to prevent excessive consumption. Although some Oxalis species have traditional edible uses, be aware of the oxalic acid content and consume them in moderation.