The elm (genus Ulmus), of the family Ulmaceae, comprises several species of leafy trees native to central Asia. The genus dates back 20 million years. Over time, they have spread to the northern hemisphere, temperate and tropical-mountainous areas of Europe and North America. Most species are first-growth trees that can grow up to 30 m tall, with a plant diameter of 10-15 m; they have broad crowns and straight trunks.