March 5, 2010

Vivipary

         My husband and I don’t care for green tomato pie, green tomato chutney, or green tomato salsa. We love homegrown tomatoes, so we store our last fall harvest in a box in the garage, where it’s cool enough that the green tomatoes slowly ripen. Each week, I pick out the yellow-to-orange colored fruit and place them in a dark blue hand-thrown ceramic bowl sitting on the kitchen counter, to finish ripening. While these tomatoes aren’t as flavorful as our sun-ripened ones, we think they taste better than the winter tomatoes we find in the stores around town.

         A few weeks ago, the last of our tomatoes sat on the counter. Some were a bit wrinkled, all not much larger than cherry tomatoes. My friend, Becky, turning up her nose when she saw them in the bowl, asked why I hadn’t thrown them out. I was defensive. “Cooked in olive oil, these taste great in a casserole or eggs.” I’m not sure she believed me.

         Several days later, preparing stuffed acorn squash for supper, I cut open an inch and a half long, firm, unwrinkled, red ‘Roma,’ and saw green. Thinking Becky may have been right—I looked closer, and saw tiny stems with green leaves sprouting from the seeds.

         Years ago, cutting open a grapefruit I’d stored in my fridge—one seed had sprouted. I’d thought it odd then, but now, with a tomato full of sprouted seeds, I wanted answers. I sent Cheryl, our technical editor for horticulture, an email to see if she’d have an interesting explanation.

         Cheryl responded, “Yep. I’ve seen this too, with seeds germinating inside the fruit. Did you know that corn, dried on the stalk, will germinate right on the plant? I think this would be a good one for Dr. Bob.” She forwarded my e-mail to her husband.

         Dr. Bob replied, “The technical term for this sort of thing is ‘vivipary.’ The juice of some fruit, such as tomato, apple, and some citrus, contains germination inhibitors that prevent the seeds from germinating in the fruit. Over time, in storage, those inhibitors become ineffective, allowing germination to occur. Additionally, seeds of many fruit—mostly fruit of woody plants—require a period of cold before they can germinate. So, if you store fruit in the refrigerator for any length of time, the cold requirement is satisfied AND the germination inhibitors break down, allowing the seeds to germinate in the fruit. Fruit in this condition is not harmful, but because it is old, it may not taste very good.”

         There you have it—vivipary….

         I chopped up the rest of my tomatoes that evening—none of the others had sprouted and they tasted great with the stuffed acorn squash. Later, I planted the sprouts, leaving them on the tomato slice, in a small pot, barely covering them with soil. Two seeds have grown; one is an inch tall. We’ll see if they’ll bear fruit this summer.

—Rilla Esbjornson