This is a real interesting topic, there could be so many variations. It's like the same theory as a cover crop when it comes to the nettles. One year we had almost an infestation of tiny nettle plants, that was a very good year, when I think about it!
There's alot to speculate about when it comes to how the soil is affected. Whether you can grow companion plants as you do with vegetables would be a good research topic. I learned a hard lesson this year with having tomato plants too close. The tomatoes never turned red & the plants near them were shorter than the rest. Ended up taking out the tomatoes & flushing the soil really good. So my advice is to just make sure the companion doesn't turn into a leach!
There's alot to speculate about when it comes to how the soil is affected. Whether you can grow companion plants as you do with vegetables would be a good research topic. I learned a hard lesson this year with having tomato plants too close. The tomatoes never turned red & the plants near them were shorter than the rest. Ended up taking out the tomatoes & flushing the soil really good. So my advice is to just make sure the companion doesn't turn into a leach!