Shamrocks are enough to drive a naturalist nuts. Scholars, florists, and the Irish argue the credentials of at least eight different species as the true shamrock of St. Patrick.

Legend says St. Patrick picked a small, green, three-leaved plant to explain the Christian concept of the Trinity to the Celts he had been sent to Ireland to convert. But what plant did he pick?

Many argue that the original shamrock was a clover, and five of the contenders are indeed clovers of the genus Trifolium. A variety of white clover — the same species you probably have growing among the grasses in your lawn — is even sold in small pots every year specifically to celebrate St. Patrick's Day.

But many of the earliest written references to shamrocks indicate a plant that was edible. Having tried to eat clover leaves, I would say they don't taste good enough to have been a popular food plant among the Celts. There is, however, another common three-leaved contender that's quite tasty. It's an Oxalis, or wood sorrel. The local wood sorrels I myself pick to nibble on in the summer — yellow ones I call "sour grass" — have delicious little leaves. They are tart and refreshing and could well be related to an edible Irish wood sorrel.

But edibility isn't a very strong argument when it comes to popular symbols, so let me offer another consideration. If you look at most drawings of shamrocks, they have leaflets that are heart-shaped. If you think of the common clovers that grow in your lawn, their leaflets are round. So both art and edibility point toward the heart-leaved wood sorrel.

I'm not sure the identity of the true Irish shamrock will ever really be known because St. Patrick's three-leaved plant pre-dates the scientific naming of plants. At the time he was converting the Celts, all little three-leaved plants were called seamrags. Furthermore, he may have picked both clovers and wood sorrels, whichever was close by when he needed it.

So maybe popular preference is more important than botanical correctness in this matter of shamrocks. Keep an eye on whatever shamrocks you see on March 17, and you can decide for yourself whether your favorite is a clover or a wood sorrel — or maybe another three-leaved plant altogether?