The Mystery of the Shamrock


20170317AToday, March 17, is St. Patrick’s Day, celebrated wherever in the world the Irish have settled… that is to say just about everywhere. Like many North Americans, I have Irish ancestors… and I’m far from alone. About 10% of Americans and 15% of Canadians are of Irish origin.

That shamrock is the symbol of the Irish people is very well known and it’s also the official emblem of Ireland, but do you know where this tradition comes from?

Saint Patrick Plucked a Clover Leaf…

Saint Patrick during Boston’s traditional Saint-Patrick Day’s parade. Photo: Laura Siegert, Wikimedia Commons

Saint Patrick is an almost mythical historical figure. Although he probably really did exist, there are so many stories and legends about him that historians have had difficulty determining what really happened. Some even suggest there were two Patricks and that their stories have become intertwined!

Here’s a quick sketch of what might have been Saint Patrick’s life.

Born in Roman Britain around 385 AD, he was reportedly abducted by Irish pirates at the age of 16, then lived as a slave in Ireland for 6 years. It was during this period that he became a devout Christian.

Escaping from his captors, he returned to his family, studied and became a priest. In 432, Pope Celestine, learning he spoke Irish, sent him to Ireland to evangelize the hitherto-pagan Irish people, without much success at first. However, during an impromptu sermon at the Rock of Cashel, he bent over and plucked a leaf with three leaflets, explaining that it represented the Holy Trinity. That he should so readily find the Holy Trinity in a common weed impressed the pagan Irish and they began to convert to Christianity.

Patrick became the first bishop of Ireland and died on March 17, 461 (maybe!), and the trifoliate plant, which the Irish call shamrock (seamróg), became the very symbol of Ireland.

But Which Plant?

One of the potential shamrocks: lesser trefoil (Trifolium dubium). Photo: Kenraiz, Wikimedia Commons

Therein lies the mystery. What leaf did Saint Patrick pick?

The word shamrock can mean any plant with 3 leaflets. Over the years, experts have suggested that the true Irish shamrock could be lesser trefoil (Trifolium dubium), white clover (T. repens), red clover (T. pratense) or alfalfa (Medicago lupulina), all of which are in the Fabaceae family, or even wood sorrel (Oxalis acetosella), from an entirely different family. All five are common in Ireland and it fact, throughout much of the northern hemisphere.

As for the Irish themselves, a survey conducted in 1988 showed that about 45% consider lesser trefoil (T. dubium) to be the true shamrock while one third prefer white clover (T. repens)… and all the others have their share of votes as well. So, no consensus there either.

Your Own Shamrock


White clover (Trifolium repens). Photo: Ranko, Wikimedia Commons

If you find clover plants with small green leaves on sale around St. Patrick’s Day, a tradition in many countries, the plant sold is inevitably white clover (T. repens), the same clover that grows in so many lawns. It’s easy enough to grow from seed in a florist’s greenhouse, but this cold-climate plant is usually short-lived when grown in a pot and is best planted outdoors if you want to see it thrive.


False shamrock (Oxalis triangularis)

There is also the false shamrock or purple shamrock (Oxalis triangularis, formerly O. regnellii), True enough, there is nothing truly Irish about this South American plant, but if you want to grow it and claim it as a shamrock, go for it. At least it does makes a good, long-lived houseplant.

It is said that everyone is Irish on St. Patrick’s Day. So wear the green… and show off your shamrock plant, whatever it is!20170317A

Grow Your Own Shamrock Indoors


20160317BIt is said that on St. Patrick’s Day, March 17, everybody is Irish. Okay, but are you an Irish gardener? If so, why not grow an Irish shamrock in your home?

A Plant of Legend


White clover (Trifolium repens) is one of several plants sometimes touted as the “true Irish shamrock”.

The shamrock is a legendary plant with three leaflets. Saint Patrick is said to have used it to teach the Holy Trinity to the pagan Irish back in the 7th century, converting them to Christianity. The problem is that nobody really knows which leaf he used: was it a clover, an alfalfa or an oxalis? The Irish name shamrock is of no help. It means, quite literally, “small three-leaved plant”, which could mean just about anything. I figure this gives the indoor gardener a certain freedom of choice, but since neither clover (Trifolium) nor alfalfa (Medicago) make good houseplants – and since both are solidly frozen outdoors in most regions on Saint Patrick’s Day – I suggest using the oxalis as a living symbol of your Irish heritage.

An Indoor Shamrock


The original false shamrock (Oxalis triangularis) had green leaves and white flowers, but more colorful varieties have taken over the houseplant market.

The false shamrock, also called purple shamrock or love plant (Oxalis triangularis, formerly O. regnellii) is probably the best species to use as a houseplant. It is adapted to subtropical conditions and thus easier to grow in the average heated home than more temperate oxalis species. Of course, since it hails from South America, it is certainly not the true Irish shamrock… but if you don’t tell anyone, I won’t either.

The distinguishing feature of this plant is that each of the three leaflets that make up its leaf is almost triangular. They are carried on long petioles, upright at first, but eventually arching or even drooping under typical indoor conditions, forming a dome as wide as it is tall. The leaflets have the curious habit of closing at night, folding one against the other.


Most modern cultivars have purple leaves and pink flowers.

The leaves of the false shamrock were originally plain green, but there are now many cultivars with purple foliage or with a silver or metallic pink mark on the leaflets. Similarly, the five-petaled flowers, which were white in the original species, are pink in the case of many cultivars.


Rhizome (photo: Wikimedia Commons)

False shamrock grows throughout the year indoors and is almost never without flowers. Out of sight under the soil are scaly rhizomes in which it stores energy for future use. So if you ever stop watering your oxalis, it won’t die but will simply go dormant and lose its leaves. It will then grow back from its underground rhizomes when you start to water it again. That’s because plant evolved to cope with occasional droughts in its natural environment.

This makes it the perfect plant for Snowbirds, as they can leave their oxalis totally on its own for six months without having to worry about having someone come in to water it, then it will grow back quickly when they get home and start to water it again. The rhizomes are also used for multiplication. Just dig up one or two, pot them up and you’ll quickly have a pot of true false Irish shamrock to share with friends and neighbors.

How to Grow False Shamrock

This is a very easy houseplant to care for.

Average home temperatures suit it perfectly (at less than 50°F/10°C or more than 90°F/32°C, however, it may go dormant) and it adapts to most light situations, from dim to bright. However, it prefers bright light during the winter. It also tolerates dry air, although it does better in a humid atmosphere. The only truly essential maintenance is watering: to keep growing, water it regularly, whenever the soil feels dry to the touch. You can add a diluted dose of the fertilizer of your choice between March and October… but even if you do never fertilize your oxalis, it will still grow very well.

In addition, false shamrock rarely suffers from insects or diseases. If you ever detect a problem, you can quickly solve it: chop the leaves to the ground to eliminate the pest and the plant will grow back quickly. After two weeks, your plant will be healthy again, new leaves will be growing and it will soon be in bloom!

So much for the good news. On the negative side, false shamrock is a messy plant, requiring frequent cleaning. The leaves and flowers are short-lived and if you don’t remove the faded ones every three or four days, they build up and diminish the plant’s attractiveness.

Surprising Facts

Curiously, false shamrock is grown as a vegetable in many South American countries. People consume the leaves and flowers, but especially the rhizomes, serving them either as a side dish or a condiment. All have a delightfully tangy taste, like sorrel or rhubarb. Don’t overdo it though, as all its parts contain oxalic acid which is toxic if consumed in large quantities. In South America, it is generally held that you should not eat oxalis more than three or four times a week.

If you have pets (dogs, cats, etc.) be forewarned that they don’t know that they should be consuming this plant in moderation and could become sick if they eat too much. Most pets don’t like the taste of false shamrock and will stop chewing after the first nibble. However, if your little friend is given to munching plant parts, you’d do best to keep your oxalis out of its reach.

You can also use this oxalis outdoors during the summer, in pots or planted in the garden, in sun or shade. The easiest thing to do is to cut the leaves to the ground before you plant it out. That way you won’t have to worry about slowly acclimating the plant to outdoor conditions like you would with most plants you’re transitioning to outdoor growing; the new leaves that grow in will automatically adapt to outdoor sun.

This oxalis is hardy from USDA zone 7 to 10. It therefore won’t be hardy in northern climates and will have to be brought back indoors in the fall. It warmer climes it can remain outdoors all year. Unlike many oxalis species, false shamrock is not invasive and will remain in its place unless you disturb the rhizomes. Rototilling, notably, could spread them far and wide.

20160317HBeannachtai na Feile Padraig! (“Happy St. Patrick’s Day!” in Gaelic.)