Oxalis regnellii is also known by several other names, including Oxalis regnellii "Triangularis" or Oxalis triangularis. Commonly, it's called false shamrock or just shamrock. It has purple-tinged triangular leaves and is often grown as a houseplant. Certain varieties have deep purple leaves. It's a popular gift around St. Patrick's Day. Within U.S. Department of Agriculture plant hardiness zones 8a through 11, it can be grown outside. Although generally a carefree plant, there are certain hazards to be aware of when growing these lively perennials.
Although several species of Oxalis are listed in a number of databases as being invasive, the species Oxalis regnellii is not among them. However, several nurseries, blogs and forums report that these plants may be aggressive growers. It's common that certain plants not known to be aggressive can become aggressive under certain favorable growing conditions. For those that have found these Oxalis to be too aggressive for the garden, control with herbicides, by digging up portions that have strayed beyond their boundaries or by planting in containers.
Although concentrations are low, Oxalis regnellii contains the chemical oxalic acid. Oxalic acid is used for a number of industrial purposes, such as rust removal and as a solvent. As such, Oxalis regnellii contact with the skin or eyes may cause redness, burning and irritation. Although casual encounters with the plant aren't likely to cause problems unless someone is particularly sensitive, excessive or prolonged exposure to the sap may cause rashes or discomfort.
Digestive System Irritant
Although Oxalis regnellii is considered and edible plant, and several species of Oxalis are recommended for their tart flavor as an addition to salads and stir-fry. However, because of the oxalic acid content, Oxalis regnellii should be ingested very sparingly. Too much may cause mouth, throat and stomach pain, and even nausea, vomiting and diarrhea. Oxalic acid can be reduced in some foods by boiling the leaves, since some of the oxalic acid will be removed, but so will some of the nutrients.
Kidney, Bladder and Nutrient Problems
Ingesting even moderate amounts of plants containing oxalic acid, such as Oxalis regnellii, may lead to calcium oxalate kidney stones or struvite crystals in the bladder. Even if kidney stones or crystals don't form, excessive consumption of foods containing oxalic acid may cause calcium and magnesium depletion. This occurs because oxalic acid binds with calcium and magnesium and makes it unavailable to the body.