When we think of medicinal herbs, most people’s minds go right to small weeds and flowers growing at the edge of your lawn or on a roadside. We don’t usually think of trees as a source of medicine, but medicinal trees are all around us, hiding in plain sight. Historically, much of the country was forested and the people had to find medicinal uses for the forest trees to stay healthy.
Using Trees as Medicine
Using trees as medicine breaks allows for some rather interesting preparations, as just about any part of the tree can be medicinal. How do you work with medicinal wood? It’s not edible, but still, you have to find a way to extract its potent medicine. In those cases, the wood is boiled for extended periods or added to hot baths for topical use.
For the most part, medicinal trees are used in the same way as other herbal preparations. They can be infused into teas, tinctures, oils and made into salves and poultices.
Harvesting Trees Ethically
We don’t often think about ethical considerations when harvesting dandelions or invasive Japanese knotweed. Those grow in abundance, and even if you spent all day harvesting you’d hardly dent the population. Most trees are different. They take years, and sometimes centuries to mature, and a casual harvest could scar or deform a tree for life.
If you’re new to foraging, consider taking a foraging course to familiarize yourself with the ethical and environmental implications of your foraging practices. The Herbal Academy has a great online course on Botany and Wildcrafting that teaches you both botanical terms and plant identification, as well as foraging ethics.
For the most part, careful leaf and twig harvesting isn’t a big deal. So long as your conscientious and don’t take more than a small percentage of the total tree. Bark is a different matter.
Anytime you cut into the bark of a tree, you’re opening up the trunk of the tree to insects, disease and decay. If you cut around the full circumference of the tree, a practice known as girdling, the supply of nutrients is completely cut off, and the tree will die. So obviously harvesting all the bark from a living tree is not ethical or sustainable, but how much is acceptable?
Maple syrup makers drill holes in living trees, introducing a 5/16th-inch hole in the bark each year. It takes a healthy tree a full year to heal that small wound, so bear that in mind anytime you’re breaking into bark. Some trees, like beech trees, cant heal bark wounds and for that reason, they’re popular trees for lovers to carve initials and enshrine them forever. In New England, it’s possible to find old beech trees with lovers initials dating back to the early 1800’s, still clearly readable.
Some foragers stick to a 1/3 rule, and say to harvest no more than 1/3 of the bark around a tree. Even that is pretty excessive. When rodents damage apple trees in an orchard, stripping them of bark, the farmer won’t even try to bring back anything with more than 1/3 of the bark missing around the circumference. If you’re harvesting 1/3, you’re pushing the limits of that tree’s survival and crippling it for the rest of its life.
Obviously, in a survival situation, you have to do what is necessary to survive, but most of us these days are foraging recreationally and for our own education. In those cases, bark should only be removed from trees that are about to be cut, or trees that have recently come down.
According to the Herbal Academy’s Botany and Wildcrafting Course, “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.”
If you must harvest from a living tree, prune off branches and strip those of bark. Often that’s not practical, as the branches are way up in the canopy. Some trees, like scrub willows used to make willow bark aspirin, grow like bushes and it’s easy enough to harvest just a few branches for medicine.
Now that we’ve covered the basics, here’s a list of a number of trees that can be used medicinally.
Alder trees are small trees in the birch family, and most species thrive in wet zones near rivers. They produce small catkins that are edible as a protein-rich survival food, though they are bitter. Alder’s are tapped for syrup in the pacific northwest, in the same way as maple trees are tapped in the Northeast. The wood is used to smoke salmon for preservation.
Alder bark contains salicin, the same anti-inflammatory and fever-reducing compound in willow bark.
A tea made from the leaves and bark is used to treat fever. The same tea is used externally to help slowly heal deep wounds. Its astringent properties help to draw the wound together. The astringent and anti-inflammatory properties of alder tea make it useful for treating hemorrhoids, and it’s also helpful for itch relief.
Some native American tribes use an infusion of the bark to treat other types of itchy skin irritation, such as poison oak and insect bites.
A poultice of the leaves is applied to the breasts is used to suppress lactation, which can be helpful to prevent mastitis. As a mother of two, I know just how unbearably painful mastitis can be, and I wish I’d known about alder then.
Ash trees are known for their wood, and it’s commonly used for making tool handles and baseball bats. The seeds are edible, and often produced in abundance.
Those same edible seeds were used by native Americans as an “aphrodisiac, a diuretic, an appetite stimulant, a styptic, an emetic, and as a cure for fevers.” (Source) A tea made from the bark was used to treat irritation and itchy conditions, and juice from the leaves is used to treat mosquito bites.
Beech trees grow in abundance on our land, and we forage edible and nutritious beechnuts each fall. The leaves of beech trees are used Beech trees are antibacterial, and they were traditionally used by Native Americans for treating tuberculosis. Those same antibacterial leaves are also used as a poultice for burns.
Beech leaves have been used by women in the past to “bring the menses” and they have abortifacient properties, thus beech should not be used by pregnant women.
If you’re feeling adventurous with your homemade tree medicine, try this recipe for aged beech leaf tea.
Birch is one of the easiest trees to identify, and the papery bark gives it away in any season. Birch bark is antibacterial, and it was used to create storage containers that helped keep food from spoiling. The inner bark has been harvested for centuries by the native peoples in Nothern Europe, and it’s ground into a tasty birch bark flour.
We tap birch trees in the late spring after the maple sap stops running. Birch sap has medicinal properties, and it’s still used medicinally in Eastern Europe.
The book Backyard Medicine discusses the benefits of birch sap, noting that “Birch sap, birch water, or blood, had a folk reputation for breaking kidney or bladder stone and treating skin conditions and rheumatic diseases. It can be drunk in spring as a refreshing and cleansing tonic, clearing the sluggishness of winter from the system. The fermented sap also makes birch wine and country beers and spirits.”
Its also been used to treat gout, kidney stones and scurvy, and is also promoted as a nutritional supplement for newborns and young children.
Modern medicine has found that a component of birch sap, called betulinic acid, has anti-tumor properties and it’s being researched for its ability to fight cancer. It’s also showing promise in the treatment of HIV. (Source)
Cedar trees are known for their ability to grow in moist soils, and to resist rot. Those same compounds that help them resist rot also contribute to their medicinal properties.
In traditional Native American medicine, it’s an important ceremonial plant that’s burned as an incense to clear the mind.
A tea of the twigs and branches is said to cure just about everything from scurvy to arthritis and fevers. Speaking from personal experience, I’ve never vomited so hard as after my first sip of cedar tea. It tastes nothing like cedar smells, and thinking back I feel an intense urge to wipe out the inside of my mouth.
I must have gargled nearly a gallon of water, and then drunk close to a gallon more trying to wash that scourge out of my mouth. I honestly believe if I was dying of scurvy that I still might have trouble getting it down.
Still, cedar has its uses. I make an infused oil out of cedar leaves and add a few drops to our summer mosquito repellant.
Elm trees have a distinctive fissured bark and can be easily identified by their asymmetrical leaves. These days, it’s often easy to identify them as the dead or dying trees in the canopy as they succumb to Dutch elm disease.
The inner bark of the slippery elm tree (Ulmus rubra) 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.
Powdered slippery elm bark is used to soothe wounds, and it’s also thought that taking a pudding thickened with the powdered bark can help speed bone healing.
Here are a few tips on how to harvest and use slippery elm bark for medicine.
Ironwood trees are known for their strong wood, that’s commonly used in making tool handles. The tree itself produces small edible nuts inside papery catkins that look like hops, thus the common name ‘hop hornbeam.’ Ironwood trees can be tapped for syrup, just like dozens of other trees besides maple.
Medicinally, ironwood trees are interesting because it’s the wood itself that’s used. Take a few pieces of ironwood and add them to a scalding hot bath to ease sore muscles and joints.
Linden trees are one of my very favorites. They produce an abundance of fragrant blooms to feed the bees, and every part of them is edible in some way. They grow huge in moist soils, alongside maples and hemlock. The leaves are huge, bigger than your palm, which makes them easy to identify.
Linden tea made from both the flowers is used as a treatment for anxiety, insomnia and ADHD. Herbalists love it for children because it’s so gentle. We recently made a medicinal “sleepy time honey wine” using linden flowers in small batch mead.
Maple syrup is downright delicious, but the sap itself can be drunk right from the tree. Not only is maple sap refreshing and deliciously sweet, it’s also medicinal. Maple sap is drunk traditionally in Asia to strengthen bones and it has just the right mix of minerals to do the job. It has also been shown to lower blood pressure, prevent hangovers, prevent ulcer formation and support a healthy immune response. (Source)
Though they’re not valued for their lumber, poplar trees have medicinal properties. They produce a resin that’s used in treating a number of conditions from toothaches to swellings, wounds and sprains. The buds of the poplar tree can be made into a traditional remedy known as balm of gilead which is used as a topical anti-inflammatory and antibacterial salve, and it’s also used to help break up coughs.
Black walnut trees grow wild in many parts of the country, and they produce a tasty edible nut. It can be a bit bitter and astringent, but if they’re promptly removed from the outer husk the flavor is greatly improved. Black walnut husks are used as a traditional dye for hair and as an all-natural ink.
Medically, walnuts are a well known purgative which helps to cleanse the body of parasites. Friends of mine have used black walnut tincture to treat worms in their dogs.
Willow bark might be the best known of tree-based medicines. A natural precursor to aspirin, willow bark was harvested by native Americans to treat pain and fevers. Willow bark is also used externally to treat wounds. The bark is harvested in the early spring and then dried and pounded into a powder for use all year. Willow bark can is easy to harvest on your own, and the trees are often abundant in wet areas.
Our willow shrubs put on a spectacular show every spring, drawing every bee in the neighborhood with their fluffy catkins. According to A Boreal Herbal: Wild Food and Medicinal Plants of the North, “The spring catkins are high in vitamin C and can be eaten, on their own, fried up with other plants or in soups.”
Other Medicinal Trees
There are quite a few others, and I’ll add to this list over time as I learn about new medicinal trees. There are also trees that have medicinal fruit, like apples. Apple cider vinegar is used medicinally and the fruits are a great treatment for constipation.
So what have I missed? How are you using trees medicinally?