DES MOINES, Iowa — For thousands of years, people have exchanged seeds to grow terrific tomatoes or produce the perfect potato, but a new effort to loan and borrow seeds has created a conflict between well-meaning gardeners and state agriculture officials who feel obligated to enforce laws restricting the practice.

Seed exchanges have sprouted up in about 300 locations around the country, most often in libraries, where gardeners can exchange self-pollinating seeds rather than buy standard, hybrid seeds. In spots like Duluth, Minnesota, the conflict with agriculture departments has surprised gardeners and library officials, who established exchanges to meet a growing interest in locally grown food and preserving certain varieties, never thinking to examine the intricacies of state seed laws.

“It’s about the philosophy, the legacy of shared seeds,” Duluth Library Manager Carla Powers said. Its seed exchange is operated by library employees and volunteers out of a converted wardrobe. “It’s about sharing with our friends and neighbors in the community.”

Agriculture officials say they weren’t looking for a fight but felt obligated as they became aware of the increasingly popular seed libraries to enforce laws, which are largely uniform across the country.

Intended to protect farmers, the laws ensure seeds are viable, will grow the intended plant and aren’t mixed with unwanted seeds for weeds or plants. Even though most of the laws refer to “sales” of seeds, that term is defined to include exchanges — where no money changes hands.