If you had a large enough piece of tufa, would you hollow it into a trough and plant it? Why or why not?
You could make a trough out of it, but I wouldn't. Tufa is expensive, and it's properties are much more useful to plant in or on so the roots can actually penetrate the rock. Even if you were to hollow a large chunk of tufa and save the pieces, there would still be a lot of waste. (Although a good use for all the small pieces down to sand size would be as a surface mulch.)
I don't think there is enough of an advantage of using tufa for trough construction over other rock or hypertufa that would be worth the extra cost. On the other hand, if money is not a concern, it is a soft rock that would be easy to carve.
Thanks, Rick. I was curious because so many troughs are made of "hypertufa," which sounds as though the goal is a trough of real tufa. However, the only antique stone troughs I've heard of were formerly used to hold drinking water for farm animals. Tufa wouldn't hold water for long!