The ivy at Wrigley Field turns green about mid-May. Until then, the ivy is brown.
Wrigley Field wall
Ivy
1939 by Bill Veeck
Wrigley Field
It might be so that the batters don't lose their vision of the ball after it is thrown by the pitcher.
Not the poison kind.
Fish gelatin
When a baseball gets stuck in the ivy at Wrigley Field, the umpire typically calls for a ground rule double. This means that the batter is awarded second base, and any runners on base advance two bases from where they were at the time of the pitch. The ivy-covered outfield wall is part of the unique character of the park, and such occurrences are considered a natural part of the game there. Players often try to dislodge the ball, but if it remains stuck, the ground rule is enforced.
No I'm sure soem kinds of ivy will be bad for it to eat like a poison ivy it wont eat that.
Airwaves is a chewing gum made by Wrigley Company
The stick used in many ivy plants to just to stable the ivy plants. You can use whatever kind of stick you have on hand.