When do Parson Russell Terriers stop growing?

Parson Russell Terriers stop growing by around 10 to 12 months, though they will typically reach their full height by eight to nine months old before continuing to fill out for another couple of months. Once your Parson Russell pup reaches the end of their rapid growth phase around the nine-month mark, you can transition to adult dog food. This transition is best done gradually over a week to help prevent gastrointestinal upset.