When is it a good time to introduce two Polish chickens to an existing flock of four?

[Matildathegreat]

Just curious how soon I can introduce my two 11 week old Polish chickens to our Old flock of four hens? Non Polish.

 

[sumi]

Wait until the chicks are more or less fully grown (4-5 months). In the meantime keeping them penned up next to the older flock, with only a fence between them will give them a chance to get acquainted without the chicks getting harmed and it will make the future integration much smoother.