I noticed the same thing this year. Lots and lots of volunteers, I love them and try to keep them all. My petunias and nicotiana reseeded in the cracks on the front steps. After debating removing them, I decided they looked nicer than the steps so I left them. They aren't trampled yet which means the mailman steps over them like I do. That's kind of cute.

My volunteers are mostly flowers: nicotiana, petunia, verbena, cleome along with a few tomatoes. They are welcome to stay until they crowd out something else because anything that wants to grow in my heavy clay soil is welcome to stay. I noticed too that the volunteers are a lot bigger than what I planted myself.

That is cute that your mailman takes care to not trample our plants!

Re: clay soil, I agree! The areas of our that haven't been "prepared" have pretty awful soil. Beneficial stuff that grows in it is fine by me too!

Re: size. The volunteer tomatoes I transplanted to my mom's yard are the healthiest tomatoes I've ever grown.

Hey june - I've got a volunteer myself. Take a look:

Squash?

What do you think it is?