When is the best time to pick green tomatoes to make chow with?

by Ellen
(Saint John, New Brunswick, Canada)

Is it best to pick green tomatoes before any of the tomatoes on the plants start ripening?

Or should I use the ripe ones and get the green ones later on?

I find that we have too many ripe ones to keep up with! So should I pick a lot of green ones now, or wait till some of the ripe ones are used? I plan to make a big batch of green tomato chow chow.