(Editor's Note: This article was originally published on March 17, 2008. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)
History and lore
Surely the shamrock is one of the most recognizable symbols of Ireland.
The Irish have actually gone so far as to register this as a trademark, although the gaelic harp is their official insignia.
A shamrock is, of course, a type of clover (variously referring to white clover, Trifolium repens, or lesser clover, Trifolium dubium). The Irish word for ‘little clover' is seamarog, which in common usage has evolved into shamrock. According to history, the plant was used by St. Patrick to illustrate his teachings about the trinity.
As everyone knows, shamrocks are meant to bring good luck, especially, of course the ‘four leafed clover'. This is mainly an accidental variation of the regular clover, occurring once in tens of thousands. So finding one truly is a lucky feat, either that or the result of very diligent searching.
The four leaves are said to mean faith, hope, love, and of course luck for the fourth one!
Trifolium repens (white clover) is a low growing perennial herb. The runners that the plant sends out from the tip will take root and form new plants, thereby making a good ground cover. They will be happiest in full to moderate sun, in well draining soil that is kept fairly moist. They are easily started from seed, which will germinate in about a week; sow in a regular seed-starting mix, cover seeds lightly, keep moist and in a shaded place; as soon as leaves appear they should be placed in a sunny position. They can be grown as houseplants if given sufficient light (otherwise they quickly become leggy). If planted outside they will go dormant in the winter and re-emerge again in the spring.
Occasionally the appearance of white clover is not so desirable: Clover is a very common weed in lawns. Although some homeowners do not find clover objectionable, its creeping growth habit can overtake turf and form large dark-green patches.
Around St. Patrick's Day four leaf clover plants are for sale in garden centers everywhere. This plant is NOT a true clover but most often wood sorrel, Oxalis tetraphylla ‘Iron Cross', a bulb plant which is hardy in zones 7 and upwards; of course sold for its leaves, this plant will bloom with lovely salmon pink flowers in summer. It will do best in light shade and will make an attractive carpet under trees. If kept as a house plant it will decline in about 4-8 weeks; this is natural for a bulb plant, but don't throw it away! After the foliage has died back give it a cool dark place for about 4 weeks and then bring it back into the light. It should regrow quickly.
A very attractive Oxalis variety has large purple leaves, that are somewhat pointed at the tips. This is Oxalis triangularis (syn. O. regnelli).