Ever since Manhattan florist Max Schling brought some corms (bulbs) of wood sorrel (oxalis repens) from the Caucasus in 1906, the four-leaf clover has been an article of commerce. Its market: a small and variable share of the nearly $500,000,000-a-year premium and advertising novelty business (convention buttons, greeting cards, etc.).
But oxalis repens, which runs freely to four leaves, is not real clover, has telltale nicks in the leaves. This year, for the first time, oxalis raisers found their market seriously invaded by the genuine article, trifolium repens. Millions of perfect four-leaf...