The Upside-Down Tree
By Steve Roark
I’ve bragged about our areas plant diversity in the past. The mountainous terrain dissected by rivers and streams creates an incredible variety of habitats that supports more plant species than anywhere but rain forests. One example of this species richness is a tree that is not only growing far out of its normal range but has a most peculiar growth habit that helps it survive.
Northern White Cedar (Thuja occidentalis) is an evergreen tree that you may have used as a landscape plant with cultivars named “arborvitae”. The foliage forms handsome flat sprays of scale-like leaves, and the bark is reddish brown and peels into narrow longitudinal strips. The wild native tree normally grows in boggy forests of Canada and bordering northern states and can be found all the way up to the Arctic tree line. But there are isolated populations far outside of its natural range, and locally can be found along the Clinch and Powell Rivers, especially on rocky limestone cliff sites. Being able to grow in a wet swamp as well as a dry crack in a rock is a pretty wide swing of habitats, but white cedar competes poorly with other tree species for sunlight, and so being able to grow where competitors cannot give white cedar an advantage that allows it to survive.
To be so far away from its normal northern homeland, white cedar is fairly common along our local rivers and lakes. As mentioned they can be found on cliffs and rocky places, often growing literally on the rocks wherever they can find a crack with a little soil in it. Most of the trees are growing slow and don’t get to be very big, but occasionally you can find one with enough soil to reach a decent size. The moist fogs the rivers produce almost daily probably helps water the trees, allowing them to make a go of it.
An additional strategy to assure full sunlight for growth is their ability to grow upside down. Trees growing in the cracks of cliffs have pretty small root systems, and eventually the tree will grow too heavy to support it and it falls over. But the roots manage to hang on to it and so the tree continues to grow upside down and so it turns its leaves back upright, and it grows just fine, with competing trees far out of reach. Yet another example of great creation engineering to allow life to grow almost anywhere.
One other interesting thing about Northern White Cedar is their longevity. Growing in harsh conditions forces them to grow slowly, and are often gnarly, shrub-like specimens. But even small trees can be very old. White cedar is the oldest tree in the eastern U.S. and Canada, and the oldest living cedar is over 1100 years old. One dead tree was found to be over 1650 years old.
If you get a chance to float the Powell or the Clinch, be on the lookout for these amazingly tough trees.