A rough-coated collie puppy will be joining our family soon. Our plan for outdoor elimination is to place the puppy (only when elimination is imminent) in an ex-pen to keep the young pup contained while he/she sniffs and circles and to train the puppy to use just a particular section of the yard. I imagine only needing this for 2-3 months (am I too optimistic?).
Collies can grow quite big, but I can't find any reference to their size at 8-20 weeks of age and am having a hard time guessing the height of an ex-pen needed to contain a 3-4 month old puppy of that breed just for potty time.
I would like to use the shortest ex-pen possible so that my son can move it easily when he mows the lawn (or else he won't, but that's an issue for the parenting SE).
This is the first puppy/dog my husband and I have had as adults, so feel free to answer and comment with additional advice!