What about grafting from new seeding onto the old tomatoe plant? Would it produce tomatoes?

They can produce as long as they stay healthy, for even more than 2 years, but that is a challenge most everywhere, since the plant when fuiting heavily in a good season knocks itself out and is very vulnerable to many diseases and conditions.

You can graft a new seedling on the old plant, but if the old plant is sick, or beat, that wouldn't be a very productive use. The seedling scion will still need to go through its growth phases to start to fruit on its part of the plant, so if you want the variety it is usually best to start out clean and not interrupt the seedling's growing process by slicing off its roots and getting it to mend into a graft. That way you get a new, disease free plant that is in fast grow mode, and the best grafting is done when the stems are of similar size. So the reaso to graft is usually to get a new attribute like disease resistance or virile rooting for a challenged cultivar. Not to make Frankenplants just because it can be done, unless there is a benefit.

Best growing!

Perennial Tomatoes

Not something that will all take, but there are usually failures even in recovery 'chambers'. That has more to do IMO with matching the correct stem size. A side graft technique, for example on a low side shoot would be much more successful for this sort of thing, which removes the scion's roots in two stages. I would use the same procedure like when my stem broke earlier this year and only about 20% was left connected. I connected it as best I could and wire wrapped a split tube around the break and it mended just fine, although adventitious roots also grew out of the wound.

Maybe I'll try it now just to see since I have some seedlings I need to toss that were extras for my fall season. But finally we have a lower humidity week so I wait for the rain to come back and do it then.

PC