I'm sure my neighbour had no idea how big her poplar trees would get when she planted them in her garden on a very steep slope behind her house. Now they tower menacingly over the property. A mature tree reaching 150 feet could have roots extending up to 450 feet from its base and they are getting up there. Their roots have searched everywhere this dry summer for water. Every time I dig into one of my garden beds, I find a thick mat of poplar roots.
The neighbour's poplar trees
I knew this was going to be a problem, so I planted my potatoes in big tubs that I then sunk into the ground. The poplars still found their way in. Luckily, enough potatoes formed before the roots sucked the tubs dry.
I guess I'll do the same next year, but I will keep rotating the tubs to break the roots that invade them.