Recessive genes, temperature produce four-leaf clover

"What causes a clover to grow with four leaves instead of three?" asked a young writer from Vernon Area Library's "Write Away" workshop.

The tradition of good fortune on St. Patty's Day producing pots of gold and lucky charms dares optimists to hunt for the luckiest plant - the four-leaf clover.

This rare plant appears when a three-leaf variety sprouts a fourth leaf. While it might be easier to rub a rabbit's foot or find a lucky penny, go ahead and pick through the clover patch - you might actually find one. Scientists' calculate there's a .01 percent chance of landing the lucky four-leaf.

Why do some three-leaf clovers sprout four leaves? A few factors turn the standard clover into a four- and sometimes five-leaf plant. White clover is a tiny, white, spiky-looking flower framed with three green leaves. You might know it by its Irish name, shamrock. Botanists call it Trifolium.

"Some people see clover as a weed in a lawn; they want the pristine golf course greens," said Brian Lang, agronomist at Iowa State University Extension.

Clover blankets pastures and is a source of nutrition for cows, sheep and horses. Wild animals like clover, too - bears, deer and moose - and a variety of birds enjoy the seeds.

What are the chances a three-leaf clover will sprout the fourth leaf? Sure as a shamrock, it's the plant's recessive genes that are responsible for the extra leaf. Temperature can be a factor, too.

Researchers at the University of Georgia found the extra leaf, called a multifoliate, appears more frequently when the temperature rises. Not too hot, though, because clover's a cooler weather plant that thrives in a moist environment.

A lucky thing about clover - it might be the pot of gold for farmers and beekeepers.

The U.S. government pays farmers to improve nutrient-deprived soil and to plant over unused acreage. They respond by seeding soil with a cover crop of clover.

It's a low maintenance crop, Lang explains.

"Clover plants only live two to three years, but they reproduce using stolons and become long-term plants," Lang said.

Clover's sweet nectar attracts honey bees, and bees produce sweet clover honey when they draw in white clover pollen. Beekeepers sweeten the deal by paying farmers to store their beehives next to clover patches.

Check it out

The Vernon Area Library in Lincolnshire suggests these titles about good luck, Irish lore and shamrocks:

• "A Pot O' Gold: A Treasury of Irish Stories, Poetry, Folklore, and (of Course) Blarney," selected and adapted by Kathleen Krull

• "Shamrocks, Harps and Shillelaghs: The Story of St. Patrick's Day Symbols," by Edna Barth

• "Story of the Leprechaun," by Katherine Tegen

• "St. Patrick's Day Shamrocks," by Mary Berendes

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