There may be a possibility that there are some pure patternless northerns, but at the same time, I have heard the same from sources as well.
What did it for me though, is that I met a breeder in Daytona about 3 years ago, and he was a retired cop from NY, that had moved down to FL many years ago. He himself told me that he had bred northern pines with southern pines for many years, creating patternless mutt pines and CALLING THEM Patternless Northern pines, because in FL, he was not allowed to have a normal southern pine, so he did that hybridized waste of a cross to have somewhat normal looking pinesnakes. He ended it with a chuckle, like it was funny and it was no big deal. He even had some of his frankensnakes at his table labeled patternless northern pinesnakes. I was floored at his ignorance. He had been doing this for many, many years.
So, because of his lack of consideration for others, who knows how many of his frankensnakes made it out there into various bloodlines and breeding projects. Because of that, to me, anything called a patternless northern is suspect. Then again, even if they were pure, they do not appeal to me. The patterns of a northern are part of their magic and charm.
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Genesis 1:1