Thanks for all the info and advice. As usual, the folks on this board know a little just about everything.
Guess I will go out and start snipping at the shoots again. They grow so quickly I have to do it twice a year. Not sure if they are coming from a root of a nearby oak but, if so, I think I'd best avoid the chemical warfare for now.
Could also be they were acorns buried by squirrels, we have a bunch of those, and usually have so many acorns it's hazardous to go out during late summer when they drop off the trees and onto your head. Then, suddenly, last year we had no acorns. I mean zero acorns, in a wide region of our part of the country. It was in all the papers, and I never read that they identified the reason, it was a scientific mystery.
So the squirrels who didn't plan ahead for their retirement were left very hungry, and some of them started munching on the cushions of our lawn furniture. I'll be interested to see if the acorns come back this year.
Now, where are those snips?