A lenticel is a small, raised pore on the surface of a plant’s bark, fruit, or tuber that allows gases to pass in and out of the tissue underneath. Think of it as a breathing hole. When a tree or shrub develops thick, woody bark, that outer layer becomes nearly airtight, and lenticels are the openings that keep the living cells beneath supplied with oxygen while letting carbon dioxide and water vapor escape.
How Lenticels Work
Young green stems breathe through stomata, the tiny pores on leaves and soft tissue that can open and close. As a plant matures and its stems become woody, bark replaces the outer skin, and stomata are no longer present. Lenticels take over the job of gas exchange, but with one key difference: they lack the guard cells that stomata use to open and shut. Lenticels are essentially always open, which is why they also lose a small amount of water to the atmosphere.
Inside a lenticel, loosely packed cells create channels that run from the outer bark surface inward toward the living tissue beneath. These channels allow oxygen to reach cells that need it for respiration and let carbon dioxide diffuse out. The vast majority of a plant’s water loss (around 90%) still happens through leaf stomata. Lenticels contribute only a minor fraction, but their role in oxygen delivery to woody tissue is critical.
What Lenticels Look Like
Lenticels are often visible to the naked eye as small dots, dashes, or bumps on bark. Their size, shape, and number vary widely between species. On a cherry tree, they appear as distinctive horizontal lines. On birch bark, they show up as dark, narrow slits. On younger branches of many trees, they look like small raised bumps that contrast with the surrounding bark. They protrude slightly above the surface, which is why you can sometimes feel them with your fingertips.
You’ve almost certainly seen lenticels without knowing the name. The small spots on the skin of an apple or pear are lenticels. On potatoes, the tiny dots scattered across the skin serve the same purpose. Potato lenticels tend to be round and open, though those near the stolon (where the tuber connects to the plant) can be more elongated. There are also more lenticels clustered near the apical bud (the “eye” end), and those tend to be about three times smaller than the ones spread across the rest of the skin.
Lenticels on Fruit and Tubers
On fruit and tubers, lenticels handle the same gas exchange they perform on bark: moving oxygen in and carbon dioxide out. In potatoes, this exchange is essential for the tuber’s respiration during storage. Research on apples and pomegranates has shown a direct correlation between the number of open lenticels and peel permeability, meaning more open lenticels lead to greater gas exchange and faster water loss.
This matters commercially. A physiological disorder called lenticel breakdown has become a growing problem for Fuji and Gala apple growers. Before packing, the fruit looks fine. But within days of going through the packing process, the skin develops dark brown pits centered on the lenticels. The cells underneath the lenticel deteriorate and form depressions, reducing the number of apples that can be sold. The disorder worsens the longer fruit stays in storage.
In potatoes, lenticel changes during storage can actually signal what’s happening inside the tuber. Lenticels erupt (visibly swell and crack open) before the buds begin to sprout, which means growers can use lenticel eruption as an early visual marker that the tuber is breaking dormancy.
How Plants Use Lenticels to Survive Flooding
One of the more remarkable things lenticels do becomes visible when soil floods. In waterlogged conditions, roots can’t get oxygen from the soil. Some plants respond by dramatically enlarging the lenticels on their stems just above the water line. These swollen, or “hypertrophic,” lenticels act as air intakes. Oxygen enters through the enlarged lenticel, travels through spongy internal tissue called aerenchyma, and moves all the way down to the submerged roots.
Researchers demonstrated this in soybeans by introducing a traceable form of oxygen through stem lenticels. After three hours, that oxygen showed up in the roots, confirming that the stems were functioning like a snorkel. The enlarged lenticels connected to internal air channels that delivered oxygen to roots that would otherwise suffocate. This adaptation is one reason certain plant species can tolerate wet or seasonally flooded soils.
Lenticels as Entry Points for Disease
Because lenticels are permanent openings in an otherwise protective outer layer, they also create vulnerability. Bacteria suspended in water can be absorbed directly through lenticels, making them a common entry point for infection. This is well documented in potatoes, where soft rot bacteria enter through lenticels (along with wounds, eyes, and stem ends) to colonize the tissue underneath. When conditions are wet and lenticels swell open, bacterial populations can multiply rapidly inside the lenticel and surrounding tissue, causing a condition called lenticel spot, a form of soft rot.
The same principle applies to tree bark. Any pathogen small enough to pass through the loosely packed cells of a lenticel has a direct route past the plant’s outer defenses. This is why prolonged wet conditions tend to increase disease pressure in orchards and potato fields: moisture both enlarges lenticels and provides the film of water that carries bacteria inside.