The practice of consuming parts of a tree has deep historical roots across various cultures worldwide, often viewed through the lens of survivalism. When people discuss eating tree bark, they are referring to the thin, nutrient-rich inner section, not the rough, protective outer layer. This inner bark has served as an emergency food source for centuries, providing necessary sustenance during famines or harsh winters. It is a readily available natural resource that offers caloric and nutritional value in times of genuine need.
Understanding the Edible Layer
The edible portion of a tree is not the tough, external cork layer, but a structure situated just beneath it called the cambium. The cambium is a living, actively growing tissue found between the outer bark and the tree’s wood. This delicate, rubbery layer is the transport system for the tree’s sugars and starches.
Immediately inside the outer bark is the phloem, which carries sugars produced during photosynthesis down from the leaves. The cambium produces new phloem cells on the outside and new xylem cells (wood) on the inside, making this layer rich in stored energy. The cambium is thin, often only a millimeter or two thick, and is typically moist and pale in color. In terms of nutrition, 100 grams of this inner bark can provide an estimated 80 to 100 kilocalories, primarily from digestible starches and sugars, along with some vitamins and minerals.
Common Edible Tree Species
Many tree species contain an inner bark layer considered safe for human consumption, though some offer a more palatable flavor profile than others. The inner bark of most Pine species (Pinus spp.) is the most widely recognized edible variety, having been a staple for many North American indigenous groups. White Pine (Pinus strobus) is noted for its relatively thick, creamy white cambium, which can have a mildly sweet taste with a faint resinous undertone when chewed fresh.
Another widely foraged species is the Birch tree (Betula spp.), whose inner bark is often described as having a slightly sweeter flavor compared to pine. This sweetness makes it a desirable choice, although its cambium layer can be drier and more challenging to separate cleanly from the wood. Certain Maple trees (Acer spp.) also possess an edible inner bark; the cambium of the Sugar Maple, for example, can be scraped and consumed for its starch and subtle sugary taste.
The inner bark of the Slippery Elm (Ulmus rubra) is highly regarded for its sweet, nutty flavor and its mucilaginous quality. When mixed with water, this inner bark becomes sticky and gelatinous, a property historically useful for thickening soups and as a soothing herbal remedy. While the cambium of many trees is technically edible, species like the Quaking Aspen (Populus tremuloides) and various Willows (Salix spp.) are typically reserved for survival situations due to their less appealing flavor.
Processing and Consumption Methods
The inner bark is rarely eaten directly in its raw, fibrous form; preparation is necessary to improve its texture and digestibility. One traditional method involves drying the harvested strips of cambium until brittle, then grinding them into a fine powder. This “bark flour” can be used as a supplement to grain flour, commonly mixed into dough to create “bark bread,” which historically stretched grain supplies during shortages.
Alternatively, the soft, pale cambium can be cut into thin strips and boiled in water, much like a vegetable or noodle. This cooking process helps soften the fibers, making them easier to chew and digest. Some foragers also suggest lightly frying fresh cambium strips in fat until they become crisp, creating a texture similar to chips that makes the taste more palatable.
Critical Safety and Identification Warnings
Attempting to consume tree bark carries significant risks that necessitate accurate identification and careful harvesting practices. Misidentifying an edible species for a toxic one can lead to severe illness or death, as the bark of trees like the Wild Cherry (Prunus spp.) and the Yew (Taxus spp.) contains toxic compounds. Even within edible genera, certain species, such as the Ponderosa Pine, contain toxic elements and should be avoided.
It is strongly advised to only harvest inner bark from trees that are already dead or have been recently felled, such as after a storm. Stripping a complete ring of bark around the circumference of a living tree, a process known as girdling, interrupts the phloem’s flow of nutrients and will inevitably kill the entire tree. Harvesting from diseased trees or those in urban areas treated with pesticides or herbicides also introduces the risk of ingesting harmful chemical residues.