“I don’t know, exactly. It started in college. There was this sickly tree right outside my dorm window. All the other trees around it were doing fine, but this one was stunted, had fewer leaves, and those it did have were shriveled and smaller than its neighbors’. I took it upon myself to save it. It became my mission… So I watered it, fertilized it, but no good. It just got worse. So I asked one of the grounds-keepers what he thought, and he said, ‘Bad roots. Nothing you can do about bad roots.’ They were going to rip it up and plant a replacement there.”

“Don’t tell me,” Jack said. “You started a save-the-tree movement.”

“Yeah, right… ‘Woodsman, woodsman, spare that tree.’ “ She shook her head. “Believe me, between my pre-med courses and my waitressing job, I barely had time to sleep, let alone become some sort of tree-hugging activist. No, I simply read up on grafting, took a couple of cuttings—they’re called ‘scions’—from the sick tree, and cleft-grafted them onto a branch of a healthy one, then I sealed the union with grafting wax. Shortly after that, they cut down the sick tree and replaced it. But it wasn’t really dead, you see. Part of it was alive and well on its neighbor. By the time I graduated, the grafted limb was growing like crazy—easily the leafiest branch on the tree.”

Her blue-gray eyes beamed at the memory.

“Congratulations,” Jack said.

“Thank you. After that, I sort of got the bug. I go to a nursery—the plant kind—and pick out the sickliest-looking sapling. I buy it for a song, along with another healthier looking tree of the same or similar species, bring them home, and graft the runt onto the healthy one.”

“Does that make you the tree world’s Florence Nightingale, or its Frankenstein?”

“Florence, I hope. The graft union is actually stronger than the rest of the tree, and the scion usually grows faster and lusher than the understock’s own branches. But maybe there’s a little Frankenstein in me too. I’ve got what you might call a ‘lymon’ tree over there: I grafted a branch from a sickly lime tree onto a healthy lemon tree. In a few years it’ll yield lemons and limes.”

“Sure,” Jack said. “And what are you asking for that nice bridge to Brooklyn?”

“No, it’s true. You can cross-graft the same species, but you can’t cross genera.”

“You’re losing me.”

“Lemons, limes, grapefruit are all in the citrus group—one will usually accept another of the same species. But that lime scion wouldn’t have taken if I’d grafted it to, say, apple or pear understock.”

Jack walked around the room, checking out the recovering plants.

“So… you take two trees and make them into one.”