Planting

One recent sunny morning, Mr. Kress drove to a fenced field, some distance from his office and far from any other citrus tree. He unlocked the gate and signed in, as required by Agriculture Department regulations for a field trial of a genetically modified crop.

Just in the previous few months, Whole Foods had said that because of customer demand it would avoid stocking most G.M.O. foods and require labels on them by 2018. Hundreds of thousands of protesters around the world had joined in a “March Against Monsanto” — and the Agriculture Department had issued its final report for this year’s orange harvest showing a 9 percent decline from last year, attributable to citrus greening.

But visiting the field gave him some peace. In some rows were the trees with no new gene in them, sick with greening. In others were the 300 juvenile trees with spinach genes, all healthy. In the middle were the trees that carried his immediate hopes: 15 mature Hamlins and Valencias, seven feet tall, onto which had been grafted shoots of Dr. Mirkov’s spinach gene trees.

There was good reason to believe that the trees would pass the E.P.A.’s tests when they bloom next spring. And he was gathering the data the Agriculture Department would need to ensure that the trees posed no risk to other plants. When he had fruit, the Food and Drug Administration would compare its safety and nutritional content to conventional oranges.

In his office is a list of groups to contact when the first G.M.O. fruit in Florida are ready to pick: environmental organizations, consumer advocates and others. Exactly what he would say when he finally contacted them, he did not know. Whether anyone would drink the juice from his genetically modified oranges, he did not know.

But he had decided to move ahead.

Late this summer he will plant several hundred more young trees with the spinach gene, in a new greenhouse. In two years, if he wins regulatory approval, they will be ready to go into the ground. The trees could be the first to produce juice for sale in five years or so.

Whether it is his transgenic tree, or someone else’s, he believed, Florida growers will soon have trees that could produce juice without fear of its being sour, or in short supply.