"What?"
"Well," explained Karyn, "it can do anything. Including making seeds grow fast."
"But... but... I mean, we used magic and those seeds came off of me. What's going to happen when you plant them? Grow another me?"
"It might not be exactly the same as you," said Karyn. "If you plant the seeds from a fruit you might not get exactly the same fruit, because it had to be fertilized by a different plant."
"But you just created them as part of me. You didn't fertilize anything to get them."
"Well, we'll see. Maybe they're self-fertilizing, anyway." Karyn looked at the stone, but Jon didn't hand it to her.
"Come on," she said. "What can it hurt that you can't wish away later on?"
Jon sighed. "Fine," he said, and handed her the magic rock.
"Now I just need to word it," said Karyn. "I wish that, uhh, I can command anything I plant to grow or stop growing by telling it to grow or stop."
The stone flashed, Karyn handed it back, and Jon said "You're really doing it. I didn't think you would."
They went outside and Karyn found a patch of dirt on the side of the garden. It had rained last night and the soil was still damp. Karyn planted a seed in it, pushed some dirt on top, and said "Grow!" Soon a green shoot was coming up out of the ground, like on one of those time lapse pictures of plants Jon saw on TV.
While Jon and Karyn watched, the plant developed into a vine which, naturally, resembled a watermelon vine. On the vine grew a flower, which faded and dropped off, leaving a little hard sphere and some leaves that grew and lengthened. It widened and split into two, until there were two connected spheres joined by a stem and protected by a thin husk of leaves. The backs of the spheres began to turn a non-plantlike flesh tone, and expanded outwards in an irregular way as the leaves grew around them.
When the fruit was bigger than a basketball, Karyn said "Stop!" and pulled back some of the leaves to check. It looked like a human infant was inside, an infant with a green chest area, to which the main stem was attached. Karyn let go of the leaves and they snapped back. "Grow!" she said.... What age would it be ripe at, anyway?