Are holyhocks poisonous to chickens?

I'm wanting to grow hollyhocks down the outside of the chicken run. Safe or unsafe?

I am almost certain they are safe--same family as hibiscus, okra and cotton--Malvacea.

I'm also almost positive they are safe -- they're safe for humans, the buds can be used as a tea.

Thank you very much for your responces. That does make sence, okra: safe, tea: safe. OK! Great! Hollyhocks it is!