Plant oxalis where the soil is moist and well drained, but never soggy. Slightly acidic soil is best. Additionally, improve soil quality and drainage by digging in a little well-rotted manure or compost before planting. Oxalis needs a few hours of sunlight every day, but plant in afternoon shade if you live in a hot climate. Oxalis leaves may wilt during hot afternoons, but they usually bounce back when the temperature drops in the evening. Keep in mind that species with darker leaves tolerate more sunlight.