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There are certain trees that consistently remain my favorites. When I think about their common characteristics, one thing stands out: the bark. Interesting bark is always there, whether the tree is leafing out, blooming, or showing dramatic fall color. Bark remains constant whether the tree is good, bad, pretty or ugly.
Bark has become one of those things we look to when deciding on what to plant but have you ever thought about the function of bark? What purpose does it serve; and how important is it to the health of the tree? Bark is essentially dead tissue that protects the vascular system of the tree. The vascular cambium layer is just beneath the tree’s bark. The cambium layer produces and supports the xylem, which is living tissue that conducts water, and the phloem, which transports nutrients through the tree. When the living cells of the cambium stop dividing they move outwards as waste material forming the bark. How these cells are arranged and how quickly they become waste creates the variety of bark we see in nature.
Most of us do not relate to the function of bark in such scientific terms; we like it or not for aesthetic reasons. Bark can be smooth, scaly, peeling, mottled, stripped or even barbed. I appreciate bark in all its function but there are some that stand out; its bark that makes you want to touch it!
Some of the nicest trees for smooth bark are two that have a sculptural quality in their growth habit. The yellowwood, or Cladrastis kentuckea, has elephant-gray bark that you want to reach out and touch because it looks so smooth. The same holds true for many of the Japanese maples, or Acer palmatum. Many of the Japanese maples are valued for their leaf shape and color but I honestly prefer this tree when it is naked in the winter, revealing its sculptural silhouette and smooth bark. And, who can forget the European beech, Fagus sylvatica, with white-gray, silky smooth bark that towers above on a perfectly straight trunk.
Stripped and Streaked
The smooth grayish vertical streaking of the serviceberry’s trunk, or Amelanchier arborea, is subtle compared to the much more pronounced stripes of the stripped-bark maple. Both Acer pensylvanicum and Acer tegmentosum are as dramatic as it comes for stripped bark but they can be challenging to grow in an average landscape. They prefer acid, moist and well-drained soil and they must be planted as under story trees because they also like cool soil with some shade. I finally got one to take off but as luck would have it, a deer used it as a back-scratcher and I may be back to square one. It is worth the effort though, so I’ll give it one more shot.
Mottled bark is everyone’s favorite; it’s cool looking. The lace bark elm, or Ulmus parvifolia, Parrotia and Stewartia species and the sycamore all have exfoliating bark that creates a patchwork of grays, greens, browns and oranges. And, yes, even a pine tree comes with interesting bark, the lacebark pine, or Pinus bungeana.
Many of the trees that have mottled bark also have peeling bark because it is the peeling and flaking off of bark that creates the mottled effect. Betula nigra, or the river birch, is probably the most recognizable of the peeling-bark trees in the landscape but there are others that prove even more dramatic. The cornelian cherry, or Cornus mas, is a small tree with flaking bark that reveals a multi-tone trunk of cinnamon and shades of gray. On the more dramatic side, the paper bark maple, or Acer griseum, looks like it has some sort of death wish because the cinnamon-red bark is literally peeling away from the trunk and branches.