Q.My willow tree has shown lovely buds over the last 2 years but seems to be dying x
I noticed a green stem coming up from what I thought was the pot ( thinking it was a weed) but it is joined to the trunk of my willow tree x

Certified GKH Gardening Expert
You willow appears to have been grafted. The original top has died off, so you will not have the tree that you bought. It will be a different variety of Willow that was used for the root stock.
This article will help you to care for willows: https://www.gardeningknowhow.com/ornamental/trees/willow/grow-a-willow-tree.htm