So how did the driveway vegetable garden fare? Reasonably well. The tomatoes were tasty though not prolific. The crop was certainly much better than if I had tried to coax them along in the part-sun of the backyard. The peppers were quite happy, continuing to produce right up until last weekend, when I decided it really was time to start dismantling the driveway garden.
As for the watermelon and squash, that little experiment was less than successful. Each plant produced two fruits. The watermelons grew to a decent size for a "personal" watermelon. However, when cut open both had mushy inedible flesh. And the squash, while they appear well-formed, only grew to about 4 inches long - hardly enough to bother with, though I suppose I should at least cut them open and see what their interiors look like. I guess there is a reason people don't grow these viney crops in containers! Although the squash blossoms were so pretty earlier in the season, perhaps I will just grow squash as an ornamental until the flowers fade.
Next year I'll do tomatoes and peppers again for sure. I'll try some of the tomatoes that are bred to be container size, but I'll also continue with heirlooms. This year my heirlooms started out leggy, having sat for too long in partial sun before I got them transplanted into their big containers. Next year I'll start with sturdier plants, and pinch and prune before they get out of control. And I'll think of something new to try in the driveway garden. Maybe sweet potatoes. Or...?