I grew up seeing trees with bare exposed soil around them fitted between concrete, normally trash and other desirables were dumped there or a place for dogs to piss. Something so sad and natural about how trees have been used in this way. However recently I have been pleasantly surprised by the trees in my local city where native flowers, grasses and even wild fennel is thriving around the trees.
They are attracting pollinators and a whole ecosystem is benefiting from this scenario as well as the tree. Tree guilds are a method in permaculture to help sustain newly planted trees, it makes sense since the biodiversity around the tree holds moisture, exposed soil looses moisture very quickly.
Not only that it also looks so much more beautiful and natural to see a thriving eco system around the plants.
I hope that more places in cities and urban areas will use this example and allow for biodiversity to grow around the trees. The most amazing thing about this, is that it has grown on its own, mostly like by birds and other insects and mammals. Let nature take care of everything, we don't have to interfere. Less interference from us, is more abundance over all!