>>5032463
really depends on the plant. some shallow rooted plants, e.g. proteacae, are shallow rooted out of necessity and will pretty much only ever grow roots along the surface. I've got some grevilleas with roots that go a good 10+m along the ground but they turn around whenever they hit a shallow slab like a driveway rather than go down
if it's a big fuck off tall tree and people call it "shallow rooted" they probably just mean compared to those pines that grow taproots as deep as the tree is tall, and it'll happily grow well under the slab of a building if that's what you mean by nowhere else to grow, but keep in mind that when people talk about big trees having shallow roots like this it's because you see them getting ripped up by storms
do look around and do some research into the species though because sometimes shallow roots means something like ficus sp which will grow through fucking walls if you're stupid enough to put a wall in their way. if you see anyone describing the roots as invasive this is what they mean (potentially)