What other plants will form roots if you sink the stem?
Is it just the Solanacae family. Potatoes form along the stem of the plant too.

Yams (sweet potato), mints.

Thanks, I did not know that.

Mints are particularly good at it. They can become invasive. But I love them.

You probably would not want mint in your garden or landscape. That is unless you wanted a LOT of mint. It is very invasive and takes forever to remove. Every time you break a root/runner/rhizome off, and they break off very easily, that segment will root. I have my mint in a large, shallow, round ceramic bowl and it is never allowed to come close to the ground.

I agree. I keep mine containerized as well. Plus I enjoy having them outside my door on the deck. Easy to reach when I want to snip some. But maybe they could compete with the ground ivy.

My penstemons seem to make roots up their stems, too.

Tomato plants, Honeysuckle vines, Sedum. Some types of shrubs are really good at self rooting also.

This is a good list. Thanks and keep the ideas coming.
I knew about the mint being invasive, but I did not know that it rooted along the stems.