The inner bark of the Slippery Elm tree (Ulmus rubra) has been used medicinally for generations. It’s part of the traditional native American pharmacopeia, where it’s used to treat digestive ailments as well as cough and sore throat. The inner bark is soothing and contains mucilage that can help mucous membrane issues.
It’s most commonly used to soothe the digestive tract, and it’s still sold as a herbal supplement to treat sensitive stomachs. I’ve taken slippery elm bark lozenges for sore throats with great success, and I can attest to how soothing it can be on a tender, scratchy throat.
Powdered slippery elm bark is used to soothe wounds and burns. It’s also thought that taking a pudding thickened with the powdered bark can help speed bone healing.
Identifying Slippery Elm
Slippery Elm is an elm species native to much of the Eastern and Central United States. It can grow up to 60 feet tall, but with the prevalence of Dutch elm disease and Elm Yellows, it rarely gets that big. Slippery elm looks very similar to American Elm, and the leaf shape may be a good way to tell them apart.
Both leaves are asymmetrical at the top, with one side coming up slightly higher on the leaf stem. Slippery Elm leaves come down to a rather abrupt point, and to my eye, it looks a bit like an extra tail hanging off the end of the leaf. American Elm leaves come to a more rounded point.
Harvesting Slippery Elm Bark Ethically
Even though slippery elm bark is still used in modern medicines, there’s been no large-scale effort to cultivate them for medicinal purposes. Couple that in with a few exotic elm tree diseases recently imported into the United States and wild elm populations are in decline.
Given that wild populations are in decline, is it ethical to harvest slippery elm bark?
In the Herbal Academy’s online Botany and Wildcrafting Course (a great resource for beginning foragers), slippery elm is specifically called out as an unsustainably harvested wild bark:
“As a rule, never harvest from the trunk of a living tree. Only harvest bark from a tree that has been recently cut down for some other reason or has recently fallen over on its own. The timing here can be tricky, as you only want to harvest from recently fallen trees (within a few weeks of falling or being cut down) and not those that have begun to rot and decay. Never, absolutely never, cut a tree down simply just to harvest its bark or its root bark. This is not only unethical, but unsustainable, and is the reason why so many tree species used in herbalism, such as slippery elm (Ulmus rubra), are currently at risk from over-harvesting.”
Given that, it’s best to harvest slippery elm bark from low branches or coppicing stumps from fallen trees. Commercially, the “best size” for harvesting slippery elm bark is a 10-year-old tree, but when you’re harvesting for your own home use, any small branch will do. The bark pulls away easily, even from the smallest branches.
There are a few cases where it makes sense to intentionally harvest a whole slippery elm tree and make use of its bark. There’s a leaf yellowing disease (Elm Yellows) that causes the whole crown of a slippery elm tree to turn yellow in mid-summer. Shortly after that, the tree then drops its leaves.
There’s no cure for this disease, and it can spread quickly to other trees. Trees with early leaf drop should be harvested immediately, and if caught early enough it may still be possible to use the bark from these trees. The disease attacks the inner bark, so in many cases, it’s not noticed soon enough to save the bark.
We recently lost a tree to Elm Yellows, and as it died it dropped a branch and broke the glass on our attached greenhouse. There was another smaller elm next to it, and it’s not experiencing symptoms yet. Still, given how close it is to the house and greenhouse, I’m not taking any more chances.
Broken greenhouse glass is expensive, and there shouldn’t be trees right up next to a greenhouse in any case. Since that elm tree is going to be cut anyway, I might as well make use of the bark.
How to Harvest Slippery Elm Bark
It’s best to harvest tree bark in the spring, just as the buds are breaking. As the sugary sap rushes up from the roots, the inner bark swells and fills with minerals and nutrients. All that extra liquid makes the inner bark more pliable and easier to remove.
Realistically though, bark can be harvested anytime a tree is about to be cut, or within a few weeks of a tree coming down. That way you can make use of what’s available and never feel the need to intentionally cut a tree just to harvest the bark.
The outer bark of Slippery Elm is soft and corky, and a knife will go right through it. The inner bark is moist and fibrous, and once it’s scored down to the wood, a strip of bark will pull away easily.
Once you’ve pulled the bark off in strips, the next step is to remove the corky outer bark. When I harvested birch bark for birch bark flour, I slipped a knife between the layers and the papery outer bark peeled off in a sheet. Not so much with Elm bark.
The bark is corky, and pieces will pop off but it doesn’t come off in convenient sheets. My 3-year-old grabbed a piece and started playing with it, and she discovered that the outer bark falls away easily if you roll up a strip. I saved a lot of time with this technique thanks to my curious little one.
When harvesting a tree that has already been cut, foragers use a draw knife to scrape off the outer bark before scraping deeper to harvest the inner bark.
Once the inner and outer bark are separated, the inner bark can be dried for later use. Peel it apart into narrower strips to help it dry more easily, and it will make it easier to grind the bark into a powder for other uses.
Once you’ve harvested and dried the bark, there are a number of different ways to use slippery elm bark.
Slippery Elm Bark Tea
A tea is the simplest way to take slippery elm bark. Years ago I used a tea from Traditional Medicinals called Throat Coat, which contains slippery elm bark and you can feel the soothing coat as it goes down.
It’s soothing to more than just the throat and it’s used to treat the entire digestive tract, from the throat all the way to the colon. Herbalists sometimes suggest taking slippery elm bark with other medicines because it has a coating effect, and it’ll coat the digestive tract and help the other medicines adhere where they’re most needed. Other sources warn that slippery elm bark may slow the absorption of other medicines, and so use your best judgment.
Slippery elm bark tea is used to treat:
- Constipation and diarrhea (stabilizes the lower digestive tract)
- Gastric Reflux
- Sore Throat
- Stomach Pain
Slippery Elm Bark Lozenges
I’m most familiar with slippery elm bark in the form of powdery lozenges made by a company called Thayers. They’re made by mixing the powdered bark with a bit of water and honey and then forming them into lozenges. The lozenges are formed by rolling the paste out and then cutting out round lozenges with a small cookie cutter or something like a water bottle cap.
Taking a slippery elm bark lozenge is a bit like taking tums. It’s a bit chalky and powdery, and it can be sucked or chewed for equal effect. The slippery elm bark powder combines with your saliva to create a mucilage that coats your throat and digestive tract.
To make slippery elm lozenges, dissolve 1 tablespoon of honey in 1/4 cup of water or herbal tea. Place 1/2 cup slippery elm bark powder in a bowl and slowly drizzle the honey/water mixture into the powdered bark.
Knead the mixture, and add more liquid if necessary to form a dough. Roll it out and cut out individual lozenges. Allow the lozenges to dry overnight or until they reach the desired consistency.
I’ve seen other recipes that just use honey and no water, so experiment on your own. For a sore throat, a honey and powdered slippery elm bark lozenge might be just the right medicine. For an upset stomach, less honey might be the right medicine.
Slippery Elm Bark Gruel
A gruel made out of the powdered bark is said to be comforting to the elderly and ill, and medicinal folklore suggests that it can help broken bones heal faster. Whether or not it helps with broken bones, it almost certainly helps treat digestive tract issues.
Slippery Elm Bark Salve or Poultice
Externally, slippery elm bark is also soothing to the skin. A herbal salve made with powdered bark or a poultice made with water and bark is used to treat wounds, boils and burns. I’ve read that Native Americans used to use moistened strips of the bark as bandages, wrapping them around wounds rather than preparing a poultice.
Other Medicinal Barks
Slippery Elm is just one tree with edible or medicinal bark, but there are plenty of others. I wrote up a tutorial on how to harvest willow bark to make willow bark aspirin, and another on harvesting birch bark to make a wildcrafted flour. While many people think of herbalism as mainly using wild weeds, there are a surprising number of medicinal trees and all it takes is an open mind to accept them into your home herbal practice.