I've never grafted anything, but I've read that potato fruit (sometimes referred to as potato berries) are pretty rare, unless you're planting Yukon Gold.

So I'm not sure how many tomatoes you'd get. Maybe more on Yukon Gold rootstock? But then again, perhaps your blue potato variety also has a high fruiting rate. You won't know till you try, so go for it!

[In case people don't know, potato fruit are poisonous. And potatoes never come true from seed -- but that's how new varieties are developed.]

I assume you have read the current discussion about this over on the Vegetable Gardening forum?

Dave

Yup, I'm watching both of them.

Figured there would be people in each forum that didn't visit the other though, so I'd get better luck with two threads. One aimed at the tomato people, and one aimed at the potato people. =)

Could someone post the link to the Discussion going on in the Vegetable gardening forum? I cannot find it. Much thanks!
I really want to try to do this.

I know tha basics of that kind of grafting.
You have the two seedlings side by side.
Make small cuts (partial removal of stems. Then wrap them together until they kind of weld together.
Then cut off the top of one(potato) and the stem of the other one(Tomato). Now you have top of tomato and root of potato.
But it is easier to be said than done, I think.

Potato berry can produce seeds(like tomato seeds) If you plant them you will get potato plant.

Nevr tried the actually grafting, but the pomato was a standard advertisement in the Sunday supplements (newspapers) in the 60's and 70's. The one I remember that named the varieties used the Subarctic tomato grafted onto a Red Norland potato