Hmm. There is a large colony of blueberry bushes in N. PA which is like this. I.e. all the plants are genetically identical; they are all one big clone.,
Yes, but it’s not the same tree, itself. Box huckleberry does the same thing, and crustose lichens that one can see on boulders, in excess of a certain size are older ‘n hell, too.
But I think the oldest living thing, so far, would be the bristlecone pine found in Nevada and California. Right up there anyway.