You're welcome.
I just wanted to say that it could be, that the wild birds are taking the berries and sowing the barberry away from Your farm, that's why You don't find new plants growing from the seeds.
Like we have (and accept) a case, when the birds are throwing down the seeds of Sea Buck-thorn (Hippophae) right under utility pole simply sowing it that way. They take these berries from my neighbour's farm.
But ... just took a look at my book, where it is mentioned, that the barberry seeds are ... poisonous, if we speak about the same barberry (Berberis vulgaris). The berries are not, just their seeds, which should be separated in case if You'd like to use them.
So - sorry, but no answer to be suggested :confused3:
How does the barberry help You to keep the deer away? (That's my issue as well) Do You form a fence of them?