The tallest Leyland cypress presently documented is about tall and still growing. However, because their roots are relatively shallow, a large leylandii tends to topple over. The shallow root structure also means that it is poorly adapted to areas with hot summers, such as the southern half of the United States. In these areas, it is prone to develop cypress canker disease, which is caused by the fungus Seiridium cardinale. Canker causes extensive dieback and ultimately kills the tree. In California's Central Valley, they rarely live more than 10 years before succumbing, and not much longer in southern states like Alabama. In these areas, the canker-resistant Arizona cypress is much more successful. In northern areas where heavy snows occur, this plant is also susceptible to broken branches and uprooting in wet, heavy snow. The tree has also been introduced in Kenya on parts of Mount Kenya.