Been growing for years...but had the strangest thing happen this year.....went to till the manure patch that I planted in last year, only to find 6 plants thriving where I had left small underdeveloped clones in the Fall. the clones had been over shadowed completely by other plants, so there was no point in pulling. They are definitely NOT seeded from the plants grown last year, as I did not get any seed from the harvested plants...let alone enough to plant six in the exact place they were left in. Wondering if the heat of the manure pile somehow kept them alive to rejuvenate in Spring? I'm in Canada
It's not unheard of for cannabis to re-veg and go perennial. It is very uncommon for it to do that anyplace except for the tropics. That being said, life finds a way....
Perhaps your plants have a genetic mutation that allows for this in a cooler climate. Perhaps it was the heat from decomposition that kept the root systems alive. Personally, I would experiment with these little guys. Imagine if you were the one that bred a cold hearty weed crop?