Thus...it appears that we have some Volunteer Lettuce, folks!
What's Volunteer Lettuce? It's a bonus plant. From Wikipedia in the Botany section:
In gardening and agronomic terminology, a volunteer is a plant that grows on its own, rather than being deliberately planted by a farmer or gardener. Volunteers often grow from seeds that float in on the wind, are dropped by birds, or are inadvertently mixed into compost. Unlike weeds, which are unwanted plants, a volunteer may be encouraged by gardeners once it appears, being watered, fertilized, or otherwise cared for. The action of such plants – to sprout or grow in this fashion – may also be described as volunteering.Seeds floating in the wind or dropped by birds! Yeah...that's the most interesting part. This little plant is growing in the driveway about 70 feet away from the raised beds. *Something* must have happened to get the seed(s) in the driveway. But...I suppose that doesn't matter. We just have to figure out a way to let the little lettuce plant grow and survive, then chop it down and eat it, right?
I've had some luck with yellow tomato volunteers in the past here on the blog.
...Off I go to figure out when the prime time to harvest lettuce greens is this summer.