|Do Giant Bird of Paradise roots sprawl out or are they a ball? Meaning, can their roots damage concrete from creeping underneath or do they typically have a ball structure? Same question for Queen/King palms.
|Strelitzia nicolai has an agressive root system which sends out suckers so the plant tends to colonize if not regularly dug and divided. I don't think they'll damage a concrete sidewalk, though. The roots will creep out in directions where there is no concrete barrier.
Palms typically have narrow, deep root systems and should not bother walkways at all.