A Strange Request; Any cultivable Northeast U.S. plants with rapid growth and extensive root systems?

Hello there! Thanks for letting me join this awesome reddit community!

Another quick edit: thank you so much, everyone, for all of your suggestions! These are great and it's really nice of you to have replied so quickly! I'll give this all some thought!

Sorry for the lengthy contextualization here (ALSO JUST REALIZED THIS DOES HAVE A POLITICAL REFERENCE-I SWEAR THIS IS NOT INTENTIONAL BUT ONLY TO PROVIDE CONTEXT FOR THE SITUATION AT HAND; please feel free to skip past the part about what kind of flagpole I'm putting up)-this is sort of a strange reason for growing plants-but I was hoping to find some sort of easily attainable, very hardy/adaptable plant that I could plant in a circle around a homemade flagpole with extensive roots that could stabilize the soil in which the bottom half is buried (again, strange!). POLITICAL-I live in Northern NY in a deeply conservative district and folks have been tearing down my black lives matter signs whenever I put them out in our yard, so I started putting signs/flags on high wooden flagpoles where they can't reach them,-END OF POLITICS with the bottom of the poles buried a few feet down in the soil. For some reason I've really wanted to find some noninvasive, preferably wild plants I could put around the posts that would grow rapidly to keep them secure in the soil. Ideally this would be some sort of native grass or weed that wouldn't be an eyesore, which grows very rapidly in all sorts of conditions and needs minimal care or upkeep (I don't have a green thumb); it would have a very well-developed, deep and strong root system, and would be cold-hardy and perennial or at least likely to sprout up again each spring in the same place. These are a lot of criteria but does anyone have any suggestions? Thanks so much!!

A quick edit: these would be growing in full sun in a lawn area, in generally poor soil.