red clover and alfalfa are not recommended for cats to chew on as they can cause nausea and vomiting and are listed in the toxic plants for cats.
http://www.sniksnak.com/plants-toxic.html
There isn't much information on barley but from what I have seen it is considered non toxic.
Any herbs or grasses that cats chew on should be done so under a cautious eye because too much can cause symptoms in any animal.
Theresa
A Voice for your Pet
16 years experience in animal medicine as a veterinary technician