Redwood sorrel is a perennial groundcover native to coastal central California and Washington. It spreads via creeping rhizomes to form lush carpets under trees, with bright green shamrock-shaped leaves that are sour-tasting due to oxalic acid. In spring, it produces dainty pink or white flowers on long stalks above the foliage. Redwood sorrel thrives in part-shade to quite shady areas with regular water and moist soil, making it a good choice as a low-maintenance groundcover under conifers or in shady gardens and containers.