practical examples of this, if you’re curious, include the Tūtohu Whakatupua (which declared the Whanganui River and tributaries as a legal entity), the agreement around Mount Taranaki (which grants it legal personhood), and the invalidated Lake Erie Bill of Rights (passed by Toledo, OH and was designed to allow residents to bring lawsuits on behalf of Lake Erie to protect it)
i’m not aware of one; you might be thinking of the Athens, GA Tree That Owns Itself–but as far as i’m aware none of these types of trees are actual examples of a plant with personhood/legal rights/etc. as in the examples i gave