I like to walk the Rotary Mile at the Community Park a couple times a week for variety, and the other day I finally slowed down to read a sign posted on a fence by the path, about in the southeast corner of the park. It reads:
This is a blackberry plant. The fruit is not ready to be picked until it is black. If the fruit is red, please do not pick! If the berry does not 'fall' off with a slight pull, it is not ripe. Be responsible . . . enjoy a few as you pass by.
Here's the bush -- I'll be watching to see when the berries are black!