Digorys tree

[Sir Edmond the just]

I was wandering what happened to the tree dogory planted that was suppose to not let Jadis pass.

[Col Klink]

The books don't say. But my theory is eventually the Narnians neglected it or even forgot its purpose and used it for kindling.

[DiGoRyKiRkE]

Nothing lasts forever - that is a common theme throughout the Narnia books. My guess is that eventually it just grew old and died. Perhaps fell down in a storm much like the tree in our world.

[coracle]

The impression is that it stood for a long time and protected Narnia, but eventually Jadis got in, so its power must have waned.

[puddleglum32]

I do not know how accurate this article is, but on the WikiNarnia page, it states that tree kept Narnia safe for 898 years. I personally do not ever remember seeing a number like that. Like others have stated I believed that the tree just ended up dying or being chopped down as I don't think Aslan intended the tree to protect Narnia forever. I will link the website down below.
https://narnia.fandom.com/wiki/Tree_of_Youth

[fledge1]

I just assumed it either died or something. Didnt Aslan say that as long as the tree was there Narnia would be protected or did I make this up in my mind. However, something obviously happened to it. Something to think about while bored at work today!!