I had Ruby Swiss Chard grow 3 feet tall and it keeps growing through winter too if you have mild winters. Only my White Leghorn nibbled the Ruby Chard but if a lettuce or chard is an all-green no-color variety the chickens are more willing to nibble on them.
We don't have mild winters here. Always get some snow. But, the chard did come back up on it's own this spring.

