I am happy to report that wisteria survived my first attempts at carving, some more of it have been done, rotting wood in touch with soil has been treated with fungicide coat that soaked into the wood and then it was painted with varnish called "Ship varnish" - our substitude for wood hardener. I was worried how it might affect the plant, but luckilly it did no harm and the deadwood is now hard as a rock.
Here is a picture of my daughter waiting for the full bloom that is upon us. I will make a proper photo session when the flowers fully open.