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Missouri Environment & Garden


Michele Warmund
University of Missouri
Plant Science & Technology
(573) 882-9632

Shamrocks: More Than A Bit O'Luck

Michele Warmund
University of Missouri
(573) 882-9632

Published: February 29, 2016

Do you need a bit of green to boost your good fortune? If so, lucky shamrock plants (Oxalis regnellii) with their three triangular leaflets and delicate white flowers might just do the trick. Lucky shamrocks are perennials grown from small bulbs that are sold as houseplants for St. Patrick’s Day. These plants thrive in indirect sunlight indoors with daytime temperatures from 70 to 75°F and evening temperatures between 50 to 65°F. Each night the plant’s leaflets fold up but reopen in sunlight the following day.

During the summer, plants can be kept indoors or they can tolerate outdoor conditions in partial shade. In late summer, leaves turn brown and drop when the plant enters a rest period. During this time, shamrocks do not require watering. After one to three months, when new green shoots emerge, resume watering and soon the plants will begin flowering once again. If you prefer colored foliage, the purple-leaf shamrock (Oxalis triangularis) is also available and has pale pink flowers. Another alternative is the Good-Luck plant (Oxalis deppei), which is sold as a four-leaf clover. With all these shamrock plants, take care to avoid overwatering and watch for mites that do not kill the plant, but cause discolored foliage. Also, these plants do not tolerate low temperatures and must be kept indoors during winter.

While these shamrocks are the more showy members of the wood sorrel family, there is also the yellow wood sorrel (Oxalis stricta) that grows as a common weed in lawns and disturbed areas. It has three heart-shaped leaflets that grow from rhizomes from May through October. This sorrel produces delicate yellow flowers and three-quarters inch-long capsules tapered at the tip that burst open to disburse its seeds. Historically, yellow wood sorrel was used for medicinal purposes and can be consumed in small portions. These plants contain oxalic acid that gives them a slightly tangy taste.

The official Irish shamrock is not in the wood sorrel family, but is a clover. Some believe the true Irish shamrock is the yellow-flowered clover (Trifolium dubium). According to one legend, St. Patrick used a shamrock to symbolize the Christian doctrine of the Holy Trinity to his congregation. Today St. Patrick’s Day celebrates the anniversary of his death and the shamrock represents the season of rebirth known as spring. An additional Irish tradition is to include shamrocks in the bride’s bouquet and in the groom’s boutonniere for good luck.

White clover is also considered a true trifoliate “shamrock”. Many an hour has been spent searching for a lucky four-leaf clover, which is a naturally-occurring mutation. However, you have to be truly lucky to find one growing in a lawn as it is estimated that only one four-leaf clover occurs for every 10,000 three leaf clovers. Even rarer is the occasional mutation resulting in a five-leaf clover. A more recent lore, the first, second, third, fourth, and the rare fifth leaflet of a clover represent faith, hope, love, luck, and money, respectively. To increase the odds of growing four-leaf clovers, breeders at the University of Florida began selecting and crossing plants in the late 1980’s and eventually released the Legendary Good Luck white clover where 50% of the plants grown from seed have four leaflets with a bit of dark red pigmentation near the center of the leaf.

Figure 1. The shamrock emblem used by 4-H clubs.

The four-leaf clover is also become an emblem for 4-H, which is the largest youth development and mentoring program in the United States (Figure 1). Their precursor organizations were boys’ and girls’ clubs, which had a three-leaf clover as their first emblem in 1907. Each leaflet of the clover had an H, representing head, heart, and hands. Four years later, a fourth leaflet was added to their emblem to symbolize health. In 1924, these clubs became known as 4-H, which is part of our Cooperative Extension Service and the U. S. Department of Agriculture.

Shamrocks have much to offer as an ornamental plant with fun folklore and traditions. Whether you are Irish, a devoted 4-H member, or just someone in need of a bit o’luck, a shamrock might be the plant for you this spring.

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REVISED: February 29, 2016