The walnut tree, Juglans regia, comes in a vaiety of cultivars to produce edible walnuts. The worldwide havest is about 4.5 million tonnes a year. The tree is believed to have originated in Iran and possibly started its migration with Alexander the Great in the fourth century BC. Its heartwood is highly prized by turners for its beauty and durability.
Walnuts grow to about 30m with a broad girth of about 2.5m. They typically live to 150 but have atained 400 years.
