Clover is a type of pea and is valued by farmers for a couple of reasons: Cows like to fill their faces with it; bees like to fill up on its nectar and the plant itself likes to fill its boots with nitrogen. That's to say, clover is very good at pulling nitrogen from the air and rooting it in the ground for other plants to eat. There are 300 species of clover, but the best one for the soil is known as white clover, or Trifolium repens [source: Faust].
Trifolium repens also happens to be the kind of clover that produces the lucky four-leaf aberration. That fourth leaf, it turns out, is the result of a suppressed gene that fails to be suppressed. Nobody's exactly sure what causes this to happen; but, for whatever reason, it rarely does. Very rarely [source: Olsen]. As mentioned earlier, your chances of finding a four-leaf clover are a measly one in 10,000. It's that rarity that accounts for the luck associated with four-leaf clovers. In other words, you're lucky just to find one, so it stands to reason (a certain kind of reason) that more luck will follow.
This is what scholars like to call, "magical thinking." Because of the way our brains operate, we're constantly looking for connections in order to explain the happenstance of the world around us. Magical thinking kicks in when we refuse to revise our conclusions despite all evidence to the contrary [source: Diaconis].
Take the story of Sandra and her stolen bicycle. Both she and the officer who found it attribute the happy outcome to the four-leaf clover she gave him from her collection. But a skeptic might ask how someone toting a quiver of the lucky clovers would have the misfortune of being robbed of her bike in the first place.
Magical thinking skirts around awkward questions like this and sticks to the convenient details while ignoring the inconvenient ones. That said, in this case at least, magical thinking is a lot more fun than skepticism.
In that spirit, here's a bit of clover trivia: In 2009, after studying ways to crossbreed the lucky plant, a farmer in Japan named Shigeo Obara grew a clover with 56 leaves on it! Logically, that makes it 14 times luckier than a mere four-leaf clover [source: Japan Times].