concord grapes

Despite missing most of Kabbalat Shabbat, I had a lovely [albeit shivery] time at a potluck last night in, and around, a local couple's beautifully decorated Sukkah. I wish I had more time to truly draw out the links between Sukkot and agriculture, historically and in the present. I think it would be a great topic for future resarch/a book.

Anyway, the folks had a whole bunch of concord grape vines, for which I have a particularly strong penchant, and one ofthe potluck attendees, who I think had also led services, was remarking about how they might not be kosher if they don't know who originally planted/harvested the vines, bc they were there before the current folks moved in.
is there any sort of written rule/precedent for this?

Afterwards we headed over to TBS and got a taste of some 1-yr aged etrog vodka...

Incidentally, I just discovered there was an article this summer in Tikkun about Omivore's Dilemma, my favorite book that I never finished reading.