40 Million Years Old
Elm trees first made an appearance in the Miocene period, about 40 million years ago.
Originating in central Asia, the tree has flourished and has established itself over most of North America, Europe and Asia.
Understanding how an elm tree lives and breathes is important in understanding how Dutch elm disease has spread.
Just like the human cardio-vascular system of arteries and veins, a tree has a vascular system of long thin vertical tubes. This vascular system takes the water and nutrients from the roots and distributes them throughout
In an elm, the cells that produce the vascular tubes are found just beneath the bark in a layer called the cambium. After each growing season, the inner part of the cambium dies. A new cambium is formed the next
spring. If you cut through a tree trunk, you can see the tree rings. Each ring is a cambium layer.
An elm tree has a very efficient vascular system but that also makes it vulnerable. The same qualities that allow the elm to efficiently draw water to its upper leaves also give fungi and insects easy access to the inner
workings of the tree. The fungus that causes Dutch elm disease, for example, essentially clogs the elm tree’s vascular system.
Dutch elm disease can be treated. However, because the tree’s vascular system is renewed every year, treatments have to be repeated annually.