MARBLE HILL -- Off a gravel Bollinger County road almost as winding as nearby Crooked Creek, in a low area behind the rustic family house, Dr. David Stewart is conducting an experiment.

The geophysicist and former Southeast Missouri State University seismologist is growing four-leaf clovers.

Stewart writes serious books about earthquakes and Southeast Missouri geology and runs a publishing company out of the house's second floor. But his hobby for the past six years has been an investigation into how the supposedly lucky kind of clover grows.

Stewart says he's one of the fortunates who always has been able to find the four-leaf clover in a patch of grass. That ability, along with the lack of existing scientific knowledge about four-leaf clovers, led him to grow and observe clover in all kinds of conditions -- indoors and outdoors, in pots and flats, in good soil and bad.

Three-leaf clovers can grow in the worst of circumstances, but Stewart found that plants producing four leaves thrive in warm weather, love sunshine and moist conditions, and need plenty of room to spread out.

Put clover in a confined space and it eventually will die.

The scientist discovered that the number of four-leaf clovers to be found among 1,000 stems is only three or four. But that four-leaf clovers seem to grow in clusters from a mother plant or nearby offspring.

In other words, certain clover plants inherit the ability to produce four leaves.

He also found that four-leaf clovers like their own kind. "When four-leaf clovers grow exclusively in the company of others capable of producing quadrafoiliates they seem to stimulate and cross-pollinate," he says.

In that situation, instead of finding three or four, four-leafers per 1,000, he found 60 per 1,000.

Stewart has run across five-leaf clovers and even a few six-leaf clovers, though he says the latter are merely three-leaf clovers that have melded.

To go looking for four-leaf clovers now would be fruitless. The weather won't be warm enough at this latitude until the first or second week of June, Stewart says.

His hunting secret is to stand with his back to the sun because clover is a sun worshiper, always facing the sun much like a sunflower does. In one experiment, he turned a flat around so the clover no longer faced the sun. Within two hours, 80 percent of the leaves had turned back toward the sun, he said.

He speaks on the subject of four-leaf clovers to civic clubs, giving away examples as door prizes. For church groups, he draws principles in living from his study of clover.

"Clovers know where their strength and energy come from and acknowledge this by turning toward and communing with their source of life throughout each day," he says.