Shamrocks or Oxalis?

In this month of March, when Irish heritage is celebrated, we frequently see plants for sale called “shamrocks”, but are they?

What is a shamrock? The term comes from the Gaelic word “seamrog” which means “little clover.”

The early Celtic peoples considered shamrocks as a charm against evil spirits, and this pagan tradition was adapted by Christian missionaries to represent the symbol of the Trinity. It is now an emblem of Ireland.

There are many species of clover, even just in Ireland. In 1893, botanist Nathaniel Colgan published a study in the Irish Naturalist. He wrote: “I was induced…to take into hands once more the inquiry into the species of our national badge…” He sent requests to many of the Gaelic speaking counties for specimens of the original shamrock “certified as genuine by competent authorities.” He also received roots from Trinity College Botanic Garden, and in Dublin from “three different itinerant vendors, each of whom was required to exercise the most scrupulous care in the selection of the genuine plant from the obviously miscellaneous collection in her basket.” Botanist Colgan planted the 35 specimens he received, which grew into 4 different varieties of clover, but the “decided preponderance” grew into Trifolium repens, otherwise known as white or Dutch clove, which is the clover variety that Iowans most commonly see in their yards. Today, it still appears in Ireland that more than one type of clover may be sold as “shamrocks”.

So what are we seeing in local stores this month? These are usually species of Oxalis, which is the largest genus in the wood-sorrel family. There are over 800 species of Oxalis, and they are most abundant in the Southern Hemisphere. The leaves of most Oxalis have three leaflets, and are shamrock like in appearance. Some leaves and flowers are light sensitive and tend to close up at night.

Oxalis regnelli, which is a South African native, is frequently sold in March labeled as a “shamrock”. It has the bright green leaves, which close in evening, and bright white flowers.

Oxalis triangularis is another common species, with purple leaves which have a rose pattern, and pink flowers.

Both of these Oxalis have fleshy, rhizomatous bulbs, and can be easily transplanted outside to enjoy all summer. They prefer semi-shade and rich soil, and would need to be potted prior to fall frost to assure survival. They are easy to grow indoors in good light, and can cheerfully bloom all winter. You don’t need to luck of the Irish to be successful with Oxalis!

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