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Cobb County Extension Service

Fact Sheet on Shamrock, Four-leaf Clover, Oxalis

By Rachel Swinford
Horticulture Program Assistant

email: uge1067@arches.uga.edu

Oxalis spp.


Leaflets	Flowers

Family: Oxalidaceae (Wood Sorrel)

Native: Widely distributed. Most come from Africa and South America

Hardiness: Varies by species

Growth Rate: Moderate to fast

Uses: Varies by species. Ornamental, Naturalizing, Houseplant, Weed. Due to dormant period, not used for mixed planters.

The familiar tale of the Shamrock is that St. Patrick, who is credited with bringing Christianity to Ireland, used a Shamrock to illustrate the meaning of the Holy Trinity. The Shamrock was also adopted as the symbol of the "season of rebirth."

The name "Shamrock" is used to describe several different plants. The Columbia Encyclopedia describes the Shamrock as "a plant with leaves composed of three leaflets." The plants portrayed most often as Shamrocks include white clover (Trifolium repens), black medic (Medicago lupulina), wood sorrel (Oxalis acetosella), hop clover (Trifolium minus), four-leaf clover (Oxalis deppei)

Leaflets closed at nighttime

The official Irish Shamrock (Trifolium dubium) is a yellow-flowered clover that is extremely difficult to grow indoors. Retailers and florists normally sell Oxalis plants instead. There are about 500 species in the Oxalis genus. Several of them are sold as Shamrocks, especially leading up to the March 17 St. Patrick’s Day holiday. This description applies to those Oxalis plants.

Description:	Habit:	Dormancy: None to 1-3 months. When the plant begins to look tired and lose leaves, stop watering and fertilizing. As leaves brown, pull them off and move the pot to a cool dark place. When new green shoots signal the end of the resting period, bring the plant into normal light. You can repot or simply restart normal watering and fertilization.
	Size:	Upright to 10" tall depending on variety.
	Flower:	Depends on variety. 5 petals. Yellow, white, pink, purple or red. Some open at daylight and close at night or overcast situations.
	Fruit:
	Leaves:	Dark green to deep red. Three rounded or triangular-shaped leaves. Many close up at night and hug tight to the stem until morning.
	Stem:	Delicate, herbaceous stem
	Roots:	Small bulbs, or tuberous roots. Prefers to be crowded in pot.
Planting & Maintenance:	Propagation:	Division: At the end of dormancy, remove bulbs from pot and divide small side bulbs. Replant just under soil surface. Water and keep soil surface moist to the touch. Note: If you are dividing your mother plant to give gifts on St. Patrick’s Day, repot in late fall so the plants have a good chance to recover from transplant shock and grow abundant foliage.
	Site:	Cool air, bright light. Can tolerate full afternoon sun in the winter; east or west window in the summer.
	Water:	Moist, well-drained soil. Let dry only slightly between waterings.
	Fertilization:	During active growth, every 2-3 weeks with a standard houseplant fertilizer. Follow container directions.
	Temperature:	Prefers 70-75° daytime and 50-65°F nighttime. Warmer temperatures may hasten the onset of dormancy.
	Pruning:	Snip out spent stems. Dust by giving your plant a gentle shower.
Cultivars:	Oxalis aceosella	Wood Sorrel. Three 3/4" dark green, triangular leaves. Rose-pink flowers. Height to 6 inches.
	Oxalis purpurea	Cape Oxalis. Three 3/4" dark green, diamond-shaped leaves. Cream, white or pink flowers. Height to 4 inches.
	Oxalis regnellii	Triangular leaves, olive green above and purple underneath, tuberous root. White flowers.
	Oxalis stricts, Oxalis corniculata	Weeds, small yellow flowers.
	Oxalis deppei (Oxalis tetraphylla)	Good luck plant, Lucky clover. Four 3/4 – 3" green leaves, triangular leaflets. Loose umbel-like cymes of 4-12 reddish purple flowers.
	Oxalis rubra	Pink flowers.
Problems:	Not blooming	Young plant: Too little light. Older plant: May be in need of a rest period. Some species do not give a clear indication that a dormant period is needed and may just be exhausted. A few months of dormancy is usually all that is needed for revival.
	Tall, thin, leggy	Too little light or temperature too warm.
	Yellow leaves	Usually too much water.
	Wilting	Roots drying out or too wet.
	Aphids, whitefly	Very rare insect problems.

References:

The American Horticultural Society A-Z Encyclopedia of Garden Plants, Christopher Brickell, Judith D. Zuk, 1997

UVMEXT Website, http://ctr.u vm.edu/ctr/press/00pressn26.htm University of Vermont Extension and Vermont Agricultural Experiment Station, University of Vermont.

Michigan State University Extension, http://www.msue.msu.edu/imp/mod03/master03.htmlMichigan State University Extension

The Columbia Encyclopedia, Sixth Edition. 2001

The Hyponex Handbook of House Plants, Elvin McDonald, Hyponex Company, Inc., 1975

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability.

Page last updated 02/28/01