“When I started my work, the nursery owners were getting all their seed from dealers who collected seed from wild trees,” recalls Gerhold, who continued breeding improved varieties of Scotch pine, Douglas fir, and Fraser fir trees for five decades. His research— and the long, close association between Penn State and the Christmas tree-growing industry—helped establish Pennsylvania as one of the nation’s top Christmas tree-
producing states.

Furthermore, Gerhold’s breeding program provided the foundation of improved materials that a group led by another geneticist in the School of Forest Resources, John Carlson, is capitalizing on through tissue culture. Called micropropagation, the process can produce uniform trees to aid both the farmers growing the trees and the families looking for the perfect tree for their holiday. “We are attempting to develop tissue culture protocols to propagate clones of the genetically improved Christmas trees that Henry produced through breeding.”

Surprisingly, some of the same tree-breeding methods used by Gerhold a half century ago— enclosing female flowers with little cellophane bags to keep out unwanted pollen, collecting desired pollen from male flowers, and blowing the “good” pollen into the bags covering female flowers—are still in use today. “We still do crosses the traditional way—the old way is still the new way to back up experiments and prove our discoveries,” Carlson adds. “Scientists still use the plastic bags over flowers like Henry has been doing for decades because we know that works.”

But Penn State plant genetic researchers are now also likely to be involved in isolating genes, identifying genetic markers, firing gene guns, nurturing tissue cultures, and using agrobacteria to introduce genes into cells—all in strictly controlled laboratory conditions.