Oxallis is Sorrel, Tripholium is Clover, Shamrocks are both
Most of the clover in nature is 3-leaf Tripholium, so plants with 4-leaves were thought to bring good luck to anyone who found them. Some gardeners plant Tripholium (white, yellow and red clover), to feed bees, butterflies and aphid-eating wasps. Landscapers and home-owners who prize perfect lawns spray herbicides to kill any clover that appears.
The three-leafed Shamrock worn on hats for St. Patrick’s Day is considered to represent the Holy Trinity. The name Oxalis came from the Greek oxys or sharp, referring to the plants’ acidic taste. In the 1600s people living off the land ate the protein and nutrient rich leaves and flowers of clover to improve their diets when greens were in short supply. Second only to potatoes in popularity, Oxalis tuberosa produces a widely-cultivated, edible, tuber. Source: http://www.cipotato.org.
The plants sold as shamrocks around St. Patrick’s Day are often Oxalis which has clover shaped leaves in green, red, burgundy, purple and a variety of color combinations. Oxalis flowers can be white, yellow, pink and red. They were genetically developed at the University of Florida.
The Good Luck Shamrock, Oxalis Deppei, has green leaves and pink flowers.
There are 500 Oxalis varieties that grow in lawns, fields, woodland gardens and windowsills so when ordering from catalogs for your shade garden, look for the ones that suit your needs. When the bulbs arrive, refrigerate them until you have time to put them into pots or into the ground
Oxalis acetosella, Wood Sorrel, has green leaves and pink flowers that float on top of 5-inch high clumps of leaves. Gardeners who plant it sometimes complain that it replants itself around the garden.
Oxalis tetraphylla deppei or Iron Cross is also called the Good Luck Shamrock. It is cold hardy in zones 8 to 10 so has to be brought in for the winter in colder zones. Their four leaves have burgundy centers that resemble a cross and the flowers are dark pink.
Oxalis oregano, Redwood Sorrel, hardy in zones 4 to 9, is native to the Americas. The plants spread by underground rhizomes, putting up green leaves and white or pink flowers. This variety is used as a groundcover for part-shade on the west coast.
Oxalis regnellii triangularis, Purple Shamrock, is hardy in zones 7 to 9. Its triangular-shaped leaves are deep burgundy and the flowers are pink. This variety is also sold as a bulb and is not invasive.
Oxalis versicolor, Candy Cane Sorrel, is native to South Africa and is cold hardy in zones 6 to 9. The notched leaves are green and the flowers are funnel-shaped white with a red rim.
Oxalis likes filtered or part-sun or bright indoor lighting but flowers best with some sun. Some varieties such as Wood Sorrel will pop up in the garden in the spring, bloom and then die back, or go dormant, when summer temperatures heat up. Then they return slightly smaller in the fall.
The leaves begin to yellow as the plants prepare for dormancy. Stop watering and do not fertilize. Just remove the dry leaves to keep the area free of insects.
When the plants are dormant, they can be dug and divided. Dig the entire clump and move it to a cool, dark place for a month or more and allow the bulbs to have their dormant period. The bulbs will begin to put out new leaves when they are rested. Then, move them to sunny spot, water and fertilize them for their next growing season.
Water Oxalis only when the surface of the soil feels dry but do not allow the bulbs to sit in wet soil or a saucer of water.
Bulb source: Brent and Becky’s Bulbs www.brentandbeckysbulbs.com, and (877) 661-2852.