The tree is standing on the mine or iron ore; its runes are sucking off its essence and transforming it into the essence fruits.
The description seemed nothing special; many alchemists could refine the essence, but one could not eat that essence. Their essence does not help give you a constitution of that element or advance it if you have it or help in advancing the bloodline of that element.
As I had said, these fruits could give one a constitution of the iron element if they ate it. If one already has a metallic constitution or the iron constitution, then they will strengthen it; it is the same with having a metallic bloodline or iron bloodline.
The tree is not special to an iron metal; it could take the essence of any fruit and convert it into the essence fruit in enough time.
