Horizontal lenticels accessorize river birch bark. We accessor ize our wardrobe with jewelry, scarves, belts, hats, shoes, and gloves to make a fashion statement and to create a more complete and appealing appearance. One way we accessorize our gardens is by the choice of plants. Each plant brings its unique set of seasonal ornamentation and interest with flower, fruit, fragrance, foliage, pods, and bark.

In fall when deciduous trees shed leaves and expose their bark, they share one of the most attractive accessor ies, lenticels. Go outdoors and inspect the bark of your woody shrubs and trees with a magnifying lens like a Boy or Girl Scout would do. They learn to identify trees in winter using color, shape, and size of lenticels as one shred of evidence.

Lenticels are small clusters of pore–like cells on the corky outer bark of a tree’s trunk and branches. To some observers lenticels look like pimples, warts, splits or “mouths.” Lenticels function as aerating tissue allowing for the entrance of oxygen and exit of carbon dioxide during respiration and permitting the exit of excess water absorbed by the tree.

In high school biology class, most of us viewed stomata on the underside of elodea or lettuce leaves under the microscope. Stomata are the circular openings regulating respiration, photosynthesis, and transpiration which open and close due to lipshaped guard cells.

Lenticels are analogous structures minus the guard cells used by woody plants. Lenticels offer a ventilation system for the living vascular bundles inside the tree since the major ity of the bark is made of alternating layers of suberin, an insoluble lipid, and wax, creating an impermeable barrier to gases and water.

Lenticels are of utmost importance to a tree’s cellular respiration. If lenticels are blocked, oxygen depletion occurs and tissue dies. Lenticels are often blocked by flooding or prolonged submersion of trees in water on flood plains or in swamps. Some trees put forth adventitious roots from enlarged lenticels below the water’s surface. These roots replace soil roots that die from loss of oxygen. The “ knees” of bald cypress seem to be respiratory organs covered in lenticels to aid aeration of inundated roots.

Prominent lenticels on black elderberry branch. Although all trees have lenticels, some are more conspicuous than others. The color, shape, size, and density of lenticels differ among species. Most wild and cultivated fruit trees have prominent lenticels. In Columbia eastern cottonwood, birches, goldenrain tree, mimosa, eastern redbud, red maple, hackberry, forsythia, elderberry, willows, sassafras, spicebush, and Chinese pistache are a few garden specimens with visible lenticels.

The paperbark cherry, Prunus serrula, is sought for its stunning lenticel studded bark. For the garden’s wardrobe, lenticels are a lovely winter accessory. For the tree, lenticels are a year–round necessity.

Lenticels are easy to view on birch species.

Decorative black cherry bark

Prominent lenticels on trunk of Yoshino cherry