Eastern hemlock (Tsuga canadensis) is rare and imperiled in Minnesota. There are only 10 known sites in Minnesota where the tree occurs naturally (not planted). This is a long-lived tree, lasting 500 years or more, but it is very slow growing and it seldom regenerates. The root system is shallow, which makes mature trees vulnerable to windthrow. Young trees are vulnerable to deer predation. Old trees are vulnerable to beavers, which sometimes girdle hemlocks to kill them and make room for more desirable trees. The species is also susceptible to the invasive hemlock woolly adelgid. Hemlock woolly adelgid commonly causes 70% to 80% mortality, and sometimes 100% mortality, among the hemlocks in forest stands in New England.