Silver Birch Growth
I planted two silver birches about 11 years ago. They are just inside my garden boundary with a pasture field. They get plenty of moisture and some strong winds but stand up to these without trouble.
The unusual feature is that the trees are now about 25 ft in height but their trunk girth is very narrow; probably 3 inches maximum. It tapers gradually to a feathered top.
I have not experienced such narrow girth on birches before and I wonder if it a natural feature of these particular trees or if there is another reason.