ISU Extension News

Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915


Cindy Haynes, Horticulture, (515) 294-4006,
Jean McGuire, Continuing Education and Communication Services, (515) 294-7033,

Yard and Garden Column for the Week Beginning March 15, 2002

The Lucky Shamrock Plant

By: Cindy Haynes
Extension Horticulturist
Leigh Thelen
Horticulture Student
Iowa State University Extension

St. Patrick's Day brings spot of green in the in local grocery stores and flowers shops in the form of the lucky shamrock plant. How did the shamrock plant become associated with St. Patrick's Day and Ireland?

There are many stories and fables, but the most popular is that St. Patrick, the saint who brought Christianity to Ireland, plucked a shamrock from the grass at his feet to illustrate the doctrine of the Holy Trinity to his congregation. Each leaf symbolizes the father, the son, and the Holy Spirit. St. Patrick's Day is celebrated on the anniversary of his death. The shamrock is also credited with the arrival of spring and as a symbol for the "season of rebirth."

Common Shamrock Plants
The "shamrock" that St. Patrick actually plucked was most likely white clover (Trifolium repens) and is difficult to grow indoors. Because of this, the shamrock plants that are seen in grocery stores and floral shops this time of year are species of oxalis or wood sorrel.

Oxalis leaves are clover shaped and can be shades of green, red, purple, or a combination of all these colors in one striking plant. The oxalis blossoms are white, yellow, pink or red depending on the species. There are hundreds of species of oxalis, but two that are commonly grown for indoor enjoyment are the Irish shamrock (Oxalis acetosella) and the good-luck plant (Oxalis deppei). Both have green leaves and small white or red blossoms, but the good-luck plant has white streaks running along the leaf vein. Both of these species exhibit nyctinstic movements, meaning the leaflets fold up at night or during overcast days and open during daylight hours. When selecting an oxalis, look for a plant with flowers and lush, healthy foliage.

How to Care For Shamrock Plants
Shamrock plants require direct sun for best growth and flowering. Oxalis plants usually bloom all winter if placed in a bright sunny window. These plants prefer soil that is kept barely moist and will do fine if the soil dries slightly between watering. Oxalis plants should be fertilized only when the plant is actively growing. Shamrock plants like cooler temperatures, especially when in bloom. These temperatures should be between 50-65 degrees F at night, and no greater than 75 degrees F during the day. Temperatures above 75 degrees F may induce dormancy.

In the summer months, wood sorrels should be allowed to rest or go dormant. The first sign that a plant is entering dormancy is leaf dieback. If this begins to occur, stop watering and fertilizing the plant. The leaves can be cut back or allowed to die back on their own and the plant should be moved to a cool, dark place for two to three months. At the end of the dormant period, new foliage will begin emerging from the soil. This is a signal to move the plant to a sunny window and to begin watering and fertilization.

Problems and Solutions
If the oxalis plant is tall and lanky, it needs more light or may also occur if the conditions in the home are too warm. If your plant is not blooming, it probably needs a good rest. Cut back on watering and fertilizing and let it go dormant. In two or three months, the plant will begin to grow again and should flower if it receives good care. A yellowing plant may be a sign you are watering it too much. Too little water and your plant will wilt. Shamrock plants are usually not bothered by insect pest, but are susceptible to root rot if kept too wet.

Good luck with this charming plant. If cared for properly, oxalis can be a part of your plant family for years to come.


ml: isugarden

Extension programs are available to all without regard to race, color, national origin, religion, sex, age, or disability.

News Menu | ISU Extension