From Butter and Sugar sweet corn to Thumbelina zinnia, thousands of seed packets owe their existence to Gwen Stefani and Boris Karloff. Gardeners, it’s winter and still a bit early to plant seeds.

Earl Wenger feels a kinship with the antique seed packing machine he spends his days with in the two-man seed packing room at Rohrer Seeds in Lancaster. “The man who invented it was a genius,” says ...