There is a push in many municipalities to restrict plant selection to natives only. I find these mandates to be troublesome. Here in the Chicago area the native landscape consisted mostly of prairie. Prairie plants have deep root systems that were able to penetrate the native clay soils and had the ability to withstand saturation in the spring and dry, hot summers. There is no doubt prairie plantings can be aesthetically pleasing and it is true that they are acclimated to the region and provide habitat for insects and wildlife. However, it is a mistake to think that native plants as a category are better survivors than adapted species just because of their “nativeness”. It is problematic for any plant to be located in the middle of a roadway or sidewalk, planted within manufactured soil blends, inundated with road salt and pollutants and subjected to extreme temperatures from the surrounding pavement. In addition, just because a plant is native doesn’t mean it is better at handling low soil volumes or foot traffic, soil compaction and snow piled on them by human beings and vehicles. Native plants are not necessarily easier to maintain than adaptive species either. In fact, maintenance personal not familiar with native species may misidentify them as weeds.
I am all for utilizing native plants where the site warrants it. Design guidelines would better serve municipalities if they allow biodiverse plant selections of both native and non-invasive, adapted species. The City of Chicago has an evolving plant list that evaluates plant material based on their ability to withstand roadway conditions. The list includes both native and adaptive species.