Feature Article - for release the week of  March 16, 2008

Dan Culbert - Extension Horticulture Agent

Shamrocks on Palm Sunday! 

As we wind down from a wonderful ride at the Second annual Okeechobee County Fair, a peak at the calendar shows that for Christians this is Holy Week, that time between Palm Sunday and Easter Sunday.   It comes early this year – I am told that no one alive today will ever see an Easter this early in the year.

Palm Sunday usually has me talk about palms, but this year I will tackle a subject that may be of interest to those of Irish descent in honor of St. Patrick’s Day.  On March 17^th everyone is Irish – and the symbol of the day is the Shamrock, the subject of today’s article.  It is a symbol of rebirth associated with the first day of spring, which also begins this week. 

♣ An Irish Legend ♣

Legend has it that St. Patrick used a Shamrock to illustrate the Christian concept of the Holy Trinity.  After converting the pagan Celts to Christianity, the patron saint of Ireland died on March 17 in AD 461, which is now known as St. Patrick's Day.   

References to Shamrocks as Irish symbols date from 1571 when they were worn on the lapel in support of all things Irish.  Some claim a shamrock is any leafy plant that has three leaflets.  The official Irish Shamrock (Trifolium dubium) is a yellow-flowered clover.  Because this plant is difficult to grow in containers, shamrock substitutes have found their way into the nursery trade.

Shamrock plants found in stores are most likely oxalis, while some potted specimens of clover are sometimes available for this luck of the Irish.  Legume plants commonly used as Shamrocks stand-ins include white clover (Trifolium repens), black medic (Medicago lupulina), and hop clover (Trifolium minus).  

Other substitutes with similar three-parted leaves include Common Wood sorrel (Oxalis acetosella).  And, the Lucky Shamrock (Oxalis regnellii) with three distinctly triangular leaflets is also used as St. Patrick’s Day ornamental.  This is a native of South Africa with white flowers. 

♣ Four-leaf Clovers ♣

The reputation of the Irish being lucky is well known, so what could be luckier than a shamrock?  Four-leaf clovers are well known to our 4-H club members, but in nature are unusual. If you carefully look at a patch of white clover with a good eye and a little extra luck, there is a chance that a mutated clover leaf with four leaflets can be found.   One estimate is that there are about 10,000 three-leaf clovers for every four-leaf clover, and 5-leaf clovers are also occasionally seen.

In the late 1980s, two plant breeders working on white clover began to develop a 4-leaf type clover.  They eventually found success, and in 1994 released a cultivar called Legendary Good Luck White clover.  Fifty percent of the individuals in this variety's population produce 4-leaf leaflets.  Another trait they have is their deep red leaf mark.  I have seen it sold as a potted holiday plant, and it is currently marketed to the fashion jewelry industry.

Another “four-leaf clover” is the Good-Luck Plant (Oxalis deppei).  This is an Oxalis from Mexico with its foliage divided into four leaflets.

♣ Ornamental Shamrocks ♣

Shamrocks grown as potted ornamentals are usually wood sorrels.  They come from Latin America or South Africa, and are tender, usually bulb-like perennials that vary in height from three to 12 inches.

Over 600 species of Oxalis are known, with more than 30 available as ornamentals.  The foliage colors may range from green to blue to silver or burgundy-purples to gold.  Some leaves show patterns or variegation as accented colors.  The leaves of Oxalis (Photo, right, UGa)  fold themselves up at night and reopen in the daylight.  Flowers are small and include white, pink, red, rose, purple, and orange to yellow.

 ♣ Shamrocks in the Lawn and Garden ♣

Both clovers and oxalis are considered by some to be weeds in turfgrass.  Many common weedkillers list these plants as target species on their product labels.  Clovers in lawns may actually be valuable to keep because they have the ability to take nitrogen from the air and convert it into fertilizer.

The UF/IFAS book Weeds of Southern Turfgrass lists four species of shamrock-like Wood sorrel weeds that can be found in Florida Yards.  These plants are also known as sourgrass because of their sour-lemony tasting leaves, which contain oxalic acid. They have small five-petaled flowers that produce okra-soaped seed pods that actually shoot the seed long distances.  Oxalis can also be a weed in potted plants and are known to harbor other plant pests – so weedy wood sorrels should be removed from container plants.

Both clover and oxalis are more common in cooler weather.  As our turfgrass resumes its growth in spring, it will generally crowd out these weeds.  In lawns, the best approach to reducing both clover and wood sorrel from lawns is to mow correctly, fertilize correctly and water correctly to encourage the grass to grow faster than the weeds.

I’ve placed more information on our Okeechobee web page, http://okeechobee.ifas.ufl.edu.  If you need additional information on shamrocks, please email us at okeechobee@ifas.ufl.edu or call us at 863-763-6469.  Local residents can stop by our office at 458 Hwy 98 North in Okeechobee, and visit our Okeechobee County Master Gardeners from 1 to 3 PM on Tuesday afternoons.  Happy:  Palm Sunday, St. Patrick’s Day, First Day of Spring, Easter Sunday and as always, Go Gators! ♣

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Trade  names, where used, are given for the purpose of providing specific information. They do not constitute an endorsement or guarantee of products named, nor does it imply criticism of products not named. The Florida Cooperative Extension Service - Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information, and other services to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin.  Florida Cooperative Extension Service / IFAS / University of Florida.  Larry A.  Arrington, Dean. Last update: 03/14/2008.  This page is maintained by Dan Culbert