The leaves of this 6” plant spring from the soil on thin, rather weak stems, ending in a leaf divided into three but sometimes four leaflets which gives it the common name Shamrock or Lucky Clover. Oxalis have green or purple leaves and showy flowers of white, yellow, pink and rosy red. Each four-lobed green leaflet of Oxalis deppei, syn. O. tetraphylla has a purple-brown splotch at the base and a pink flower. Commonly grown for St. Patrick’s Day it is neither a shamrock nor a clover but a wood sorrel native to Mexico and on south to Brazil, Peru and Chile. The leaves have ‘sleep movements’ – spreading open in the light of the day and closing up at night in the dark. These make a fun houseplant for early spring.
Light and Temperature
They need a good bright light with a just bit of direct sun for flowering. The more bright indirect light the more color you will have in both the leaves and flowers. Low light during dormancy is fine. A cool location during active growth, below 65°F (18°C) during the day but not below 50°F (10°C) at night, will help keep this plant more compact, in control and prolong the blooms. After an acclimation period they will benefit from a summer vacation outdoors in dappled shade when temperatures permit. Be sure to acclimatize them back indoors in the fall before the temperatures drop too low.
Water thoroughly so the water runs through when dry about 1-2” down. They can easily be over-watered, especially in a warm room, and you must be sure to empty any water from the saucer. The higher the temperature, the less water they will need. They do best with little humidity so our North American homes with forced air heat are fine.
This can be the tricky part. They need 2-3 rest periods a year and you will know when because the leaves begin to turn brown. Some are bulbs, some are rhizomes, and others are tuberous or fibrous. For any variety you can let the leaves shrivel and fall or gently remove the leaves, then gradually cut back on the watering, set it out of the way in a cool location, and do not water it for about 2-3 months for a green variety or 1 month if yours has purple leaves. Then either re-pot or begin watering again gradually. You will begin to see new growth, and soon will have a new, happy plant that you can return to a prominent place in your home.
Slightly sandy medium of 1 part aged compost, 2 parts loam or humus, 2 parts coarse sand, perlite, or pumice would be a good mix for this plant. Add 1 part bark fines for a more porous mix if your compost, loam or humus is on the heavier side. If using a soilless mix begin with 2 parts bark fines, and add 1 part sphagnum peat moss or coir, and 1 part perlite. Be sure to fertilize as recommended.
Use a ¼ diluted, balanced fertilizer each time you water during the active growing periods. Begin when you see new growth after a rest period and continue until the leaves begin to die back. Never feed it during dormancy.
Oxalis will flower profusely both in summer and winter but should have a rest period after each blooming. Winter blooms can last the whole season with enough light and cool temperatures.
Pests and Problems
Oxalis may attract aphids, whiteflies or spider mites. Because these plants have regular dormancy periods you can isolate your plant from any of your other plants and wait until the leaves fall to get rid of the pests. Be very sure that the pests cannot reach other plants and clean the area of all fallen leaves thoroughly. Wipe down all of the surfaces using a diluted 50/50 alcohol/water solution if possible.
A common ailment is rotting roots. If you suspect the yellowing of the leaves is not the normal dormancy period approaching you can take a look at the roots. If they are no longer a fresh white and are soft you may have rotted them. You may be able save it if there are bulblets or tubers that look sturdy by re-potting it but you may just have to toss the plant into the compost bin and begin again.
When grown as a houseplant it can become leggy and look overgrown and unkempt. Dormancy periods will rejuvenate the plant or you may want to divide the bulbs/rhizomes and re-pot to give it fresh medium and nutrients or to divide into more plants. You do not want to re-pot while your plant is in flower. After your plant has become dormant or after flowering you can re-pot into a larger pot if the roots are pot-bound or divide the clump of tubers/bulbs, 5-8 to a pot as described in the propagation section below.
Small pieces of rhizomatous species root readily when kept warm or with bottom heat. Propagate by division when re-potting. Some varieties have a rhizome root system (picture fresh ginger root only smaller) that travels sideways and sends up new shoots. When you take the plant from the pot, the best time is spring when the plant is done flowering or is just emerging from dormancy, gently remove as much soil as you can either with either your hands or water. You will see places where you can cut through, with a very sharp, clean knife, and divide one plant into several. Each piece must have a tuber (thick section of root) with new sprouts (buds) of leaves and some small roots to give the new section a good start. This is a great time to prune away any brown or rotted tuber or root. Fill the new pot 2/3’s full of fresh medium, add your rhizomes, and cover these with new medium. Plant the new plants the same depth as before – rhizomes and bulb depth will vary with variety. Some varieties will be bulbs. The small bulblets can be separated from the larger bulb. Plant the bulblets in a new pot and the large bulb alone. Plant them the same depth as before.
After dividing, water the plant very sparingly and keep very cool, 45-50°F, until you see new growth.
Sow seed at 55° to 64°F in late winter or early spring.
Often given as a New Year’s gift as a wish of good luck to the recipient for the coming year.
This plant is edible and has been consumed around the world for thousands of years. It is not listed on the ASPCA website as a harmful plant to pets. Caution must be paid if you have pets though. If your cat should eat every leaf of a large plant it may be harmful.
Oxalis deppei – syn. – Oxalis tetraphylla – has four-lobed green leaves with a nice reddish-brown splash at the center and a pink flower. Small bulblets that form around the main bulb are used when propagating. Blooms in winter.
Oxalis purpurea – bulbous root ‘cape oxalis’, grand duchess – succulent 3 lobed leaves and large rose flowers with a yellow base. Winter blooming.
Oxalis herrerae – fibrous root – branched and succulent-like light green leaves with clusters of bright yellow flowers on tall stalks. Can be used in hanging pots.
Oxalis martinana ‘Aureo-reticulata’ – bulb – variegated 3 lobed leaf with long stemmed carmine-rose flowers.
Oxalis regnellii – rhizome – leaves range from green to green with purple undersides, to purple to almost black with white flowers.
Oxalis rubra alba – syn. O. crassipes alba – green leaves with clusters of small white flowers above the foliage. Nice in pots.
Oxalis triangularis – purple leaves with white flowers. Need only a month of dormant rest.
Oxalis adenophylla – has many leaves, not the 3 or 4 you may wish, pretty purple flower with a bright white center.
Trifolium pretense – common red clover