When do chickens start laying?

[kaitkait]

Our pullets are between the ages of 14 weeks and 18 weeks I believe. We have started to feed them the layer feed along with the younger feed meant for under 18 weeks because they are around the age.
It is winter here but it doesn't get too chilly here. Phoenix AZ doesn't get harsh winters. Our chickens free range and I am wondering if there's a chance they will be laying soon? They are healthy and have gotten pretty big, raised them since they were babies & they get treats to supplement their diets.
Not sure of the breeds 100% but two are ameracauna chickens (still small but I think they are supposed to be), one is a Rhode Island red, and one I'm almost sure is a Plymouth rock (she's the biggest and sweetest one of the bunch)

Thanks

 

[Ozarkhomesteader]

most chicken start laying around 24 weeks of age. That is not a hard and fast rule though, i've have some wait a lot longer. They also might not start laying unless they get 14ish hours of sunlight.