When & how is best time to thin out & transplant hosta plants? T-Y

In the spring, when the shoots are just coming up is ideal, but you can thin and transplant anytime. This article should help:

https://www.bhg.com/gardening/flowers/perennials/how-to-divide-hostas/

You can do it any time you want. Spring is the best, when they are just starting to come up, it is the easiest. All you have to do know that they are already up is gently pull the leaves up into a bundle and tie them with something that won't harm the leaves, dig the hosta up, divide it, tie backup the smaller bunches to keep the leaves unharmed and plant them in the already dug holes you want them in. Hostess are tough, When I redid one of my gardens, I removed the ones that were in there and just plopped them soil and all into pots and the stayed in them for two months while I planted other hostas as I could afford them, and then planted the old ones. They did fine and the next year you wouldn't even know they were a transplant from another garden bed that we made into a seating area. They love their new home, not being under junk shrubs anymore. They were well established plants, but now are even larger and bushier than their old home two years ago because they have more room now.

I found an article that answers your question perfectly. https://www.nhhostas.com/dividing-hostas/

these are resilient plants. you need to think about where you move these as they will grow and expand with the years. they do like to grow in circles too!.

Thank you for this Hosta tidbit. You have got to be so correct because this is exactly what happened to the first site they were planted. And, getting the next site ready beforehand sounds like a very good common sense idea, one I had not given any thought to doing.