The time it takes for a pullet to begin laying varies primarily on the breed and the time of year she was hatched. A hen will usually go ‘dormant’ in the coldest seasons. This means that chicks hatched in Fall or late summer will often hold off on laying until the following spring…
When a Hen Starts Laying:
Most hens will begin lay at between 4 and 8 months of age. However, each hen is different. Even hens of the same breed may not start their first laying season at exactly the same time.
Some breeds are slower to mature than others. Generally, bigger, heavier breeds and Heritage Breeds (such as Jersey Giants) start lay the latest and the lightest, smallest breeds (Like Leghorns, Egyptian-Fayoumis and many Easter-Eggers) start lay the soonest (~4-6 months). However, many dual purpose breeds that where bred for both meat and egg production (like Rhode Island Reds, Sex-Link Hybrids and Plymouth Rocks) begin laying on the early end of the spectrum as well (~6 months or so). Some Ornamental (fancy) breeds, which are usually not bred for egg laying purposes may mature slowly (even many lightweight varieties). For this reason, many ornamental chickens, (Polishes and Crevecoeurs) may not begin laying until 7-9 months.
Notes About Expecting the First Eggs
Something to take into account when expecting eggs from pullets is that when Pullets first begin laying, the size of the egg will be smaller than average. This is normal and to be expected. Over time, egg-size will gradually increase (with healthy chickens). Additionally, hens that first lay may lay a few eggs with blood stained shells. This is also normal. (You can read more about the causes here: Blood-Stained Egg Shells). Defective eggs (such as Soft-Shelled, White-Banded & Slad-Sided) are also fairly normal for young hens coming into their first laying season. However, no egg-laying defects should be a frequent occurrence. Frequently laid, defective eggs can be an indicator of health problems.