DESCRIPTION: These are hardy and tender plants that are mostly found wild in south Africa and tropical and subtropical America, but can be found in many parts of the world, including North America. Several hardy kinds are gorgeous for the rock garden, a few are showy enough for flower borders and many are great for windows and greenhouses. Oxalis montana (the American Wood Sorrel) is a lovely plant that has green "Shamrock" leaves and white flowers veined with lilac. Since it's a woodland plant, it will flourish if placed in cool, partly shady positions. It is a nice ground covering under bushes and trees. It grows only 2-3 inches high and is a native of the cool, rich woods of North America. Care must be taken that it doesn't grow out of control and become a troublesome weed. O. violacea is another kind that grows beautifully in the rock or wild garden. It ranges from Massachusetts to Florida and westward to the Rocky Mountains. It will grow 3-6 inches high and bear rosy-purple flowers in the summer. O. corniculata is a hardy annual with creeping stems. It forms a pretty green carpet with bright yellow flowers during the summer. O. corniculata rubra is a beautiful variety that has purple foliage contrasting with the gold blossoms. Both of these varieties spread quickly so care must be taken in managing them. O. rosea is an annual, native of southern Chile. It grows 6-9 inches tall and has bright green leaves and an abundance of pale lilac-pink flowers all summer long. It will grow in dry spots and looks nice under trees. O. enneaphylla is the prettiest of all the rock garden kinds. The leaves consist of nine blue-green leaflets that are folded in a way that gives them a crinkled appearance. They are carried on pinkish, upright stems that are 3-4 inches long. The trumpet-shaped flowers are large compared to the size of the plant, being 1 to 1˝ inches across. They are white and waxy looking and have the delicious scent of almonds. This plant blooms in May and June. It isn't easy to grow in most American gardens; it is most likely to succeed in the Pacific Northwest. It needs especially cool, well-drained loam with plenty of leaf mold. It needs a cool position shaded from direct sun during the hot hours of the day. There are three shrubby kinds of Oxalis. O. gigantea is a native of Chile. It grows 6-8 feet tall and has woody branches covered with tufts of fleshy, trifoliate leaves and numerous bright yellow flowers. O ortgiesii is more common in the U.S. It grows to a height of 1˝ feet and its leaves are a rich purple underneath. It produces small yellow flowers. O. dispar is a true shrub that thrives in a moist atmosphere in a warm, tropical greenhouse. It's a slow grower and it needs the same conditions as O. ortgiesii for its successful cultivation.
POTTING:
Hardy kinds: They thrive in regular soil in light shade. O. montana and O. violacea like woodsy soil.
Tuberous kinds: These can be grown indoors or outside in mild climates. They need light, nourishing soil with adequate drainage in full sun. They need a minimum night temperature of 45-50 degrees. The tubers should be planted at the beginning of their growing seasons, which differs between the varieties, but generally, the spring blooming plants start new growth in the fall, summer blooming plants start in spring and the fall bloomers start in July or August. Six-inch pots can hold six to nine tubers (bulbs), slightly fewer in 5-inch pots. They should be covered with about an inch of soil. Give water sparingly at first, but as the leaves start to grow and the root system expands, it can be given generously. When the plants are in active growth, doses of a dilute liquid fertilizer should be given every week. As the leaves begin to die down after the flowering season is finished, water should gradually be reduced and finally stopped. The bulbs are then kept quite dry until the beginning of the next growing season. During their period of rest, they can either be left in the soil or stored in paper bags in a cool, dry spot. At the beginning of the growing season each year, they should be repotted in fresh soil.
Non-tuberous kinds: They need a sunny, frost free greenhouse or they can live outside in mild climates. They bloom in the spring and summer. They should be potted in January or February. During the active growing season, they need plenty of water. When the leaves have withered, the soil should become dry.
Shrubby kinds: O. gigantea needs to live in a cool greenhouse. O. Ortgiesii doesn’t need a season of complete rest and will thrive in woodsy soil in a humid atmosphere. The night temperature needs to be 55 degrees. O. dispar is a true shrub that thrives in a humid atmosphere in a warm, tropical greenhouse.
PROPAGATION: At the beginning of the growing season they can be propagated by offsets. They also can be raised from seeds that are sown at the beginning of the growing season of that certain kind. They can be planted in pots of light, sandy soil in a cool greenhouse or window. O. enneaphylla is propagated by breaking up the roots. The best time to do this is in the spring, just as it begins to show signs of growth. The whole mass should be lifted and split up at every joint and replanted immediately. If seed has been obtained, then it should be sown soon after gathering as possible, in pots of sandy loam and leaf mold. They should be kept shaded in a cold frame. Germination may be slow and the pot shouldn't be discarded under 18 months to 2 years.
VARIETIES - Hardy: O. montana (the Wood Sorrel); O. violacea; O. corniculata; O. corniculata rubra; O. valdiviensis; O. rosea; O. lobata; O. enneaphylla; O. adenophylla; O. magellanica; O. laciniata.
Tender tuberous: O. Bowieana; O. Bowieana (purpurea); O. cernua (Bermuda Buttercup); O. cernua variety flore-pleno; O. Deppei; O. brasiliensis; O. hirta: O. incarnata; O. lasiandra; O. lobata; O. variabilis;
Tender nontuberous: O. rubra; O. rubra alba.
Shrubby: O. gigantea; O. Ortgiesii; O. hedysaroides rubra; O. dispar.