Sackgasse. completely right, this has been in use for decades. As you mentioned, they last forever!!.
They do not shrink, create mold. smell or anything.
Yes, it varies from country to country, some call it, cold clay, salt clay, cold porcelain, etc..
On the tall grass, I may have called it wrong, it may be wheat or something else that tall...I like your suggestion on using branches , yes I will use some....in another dio...but now these are so tied by the wire that it is going to be a nightmare to take them off....so I will just leave them...lets call it experiment 101.
I found a photo of something similar being used.. in Montecassino. See the ones next to the tree.
Thanks for taking the time on the comments, they are appreciated and helps me improve.