Understanding Tree Exudates: Gums, Resins, and Oleoresins
When a tree sustains an injury—whether from wind damage, insect attack, or deliberate tapping—it responds by producing protective substances that ooze from the wound. These exudates have fascinated aromatherapists, herbalists, and perfumers for millennia, yet confusion persists about what distinguishes one type from another. The differences matter because they fundamentally affect how we extract, preserve, and work with these precious materials.
The Chemistry Behind the Differences
The key to understanding tree exudates lies in their chemical composition and solubility properties. Each type contains different proportions of volatile essential oils, non-volatile resins, and water-soluble polysaccharides (gums). These compositional differences determine not only their physical properties but also the extraction methods required to work with them effectively.
Resins form through the oxidation of essential oils within specialized resin ducts in a tree’s bark. When exposed to air, they harden into sticky, semi-solid masses. Chemically, resins consist of complex mixtures of terpenoids and phenolic compounds. They are lipophilic—meaning they dissolve readily in alcohol, oils, and fat-based solvents, but remain completely insoluble in water.
Gums, by contrast, result from an entirely different process called gummosis, where internal plant tissue breaks down to form polysaccharide-rich substances. These typically ooze from stems or branches in response to injury or disease, creating a protective barrier against fungal infection. Gums are hydrophilic—they dissolve in water but not in oils, fats, or alcohol.
Oleoresins represent a third category: fresh, liquid exudates that contain substantial amounts of both volatile essential oils and non-volatile resinous material. The prefix “oleo” refers to the oil component, making their dual nature explicit in their name.
Three Categories for Aromatherapy Practice
For practical aromatherapy work, we can classify aromatic tree exudates into three functional groups based on their extraction requirements:
1. Oleoresins (Oil + Resin)
Oleoresins combine essential oils with resinous compounds in varying proportions. Because they contain no water-soluble gum fraction, they dissolve completely in warm carrier oils or alcohol without requiring special preparation.
Examples include:
- Pine resin (Pinus species) – The pitch tapped from coniferous trees of the Pinaceae family
- Spruce resin (Picea species) – Collected from black spruce and other spruce varieties
- Elemi (Canarium luzonicum) – An aromatic oleoresin from the Philippines that hardens upon air exposure
- Copaiba (Copaifera species) – Obtained by boring holes into the heartwood of South American trees. The thick liquid that flows out is copaiba oleoresin (sometimes called “copaiba balsam”), which can be used directly in formulations or diluted in carrier oils. When steam distilled, this oleoresin yields copaiba essential oil—the lighter, more volatile fraction commonly used in aromatherapy. Both forms are therapeutically valuable, though the oleoresin retains the full spectrum of volatile and non-volatile compounds prized in traditional Amazonian medicine.
- Balsam of Peru (Myroxylon pereirae) – A thick oleoresin containing benzoic and cinnamic acid derivatives
- Balsam of Tolu (Myroxylon balsamum) – Similar to Peru balsam but with a sweeter, more vanilla-like aroma
These materials can be directly infused into warmed carrier oils or dissolved in high-proof alcohol to create tinctures. The process is straightforward because all components share similar solubility properties.
2. Oleo-Gum-Resins (Oil + Gum + Resin)
This group contains all three components: volatile essential oils, non-volatile resins, and water-soluble gums. The presence of gum creates extraction challenges because not all constituents share the same solubility characteristics. The gum fraction acts as a protective coating around the resinous and oily components, preventing direct dissolution in oil or alcohol.
Primary examples:
- Frankincense (Boswellia species) – Including B. carterii, B. sacra, B. frereana, and B. serrata
- Myrrh (Commiphora myrrha and C. erythraea) – The characteristic oleo-gum-resin from East Africa and Arabia
The substantial gum content in frankincense and myrrh explains why these materials won’t fully dissolve when placed directly into warm oil. Instead, they must first be ground into fine powder, which exposes the inner resinous and oily constituents to the solvent. Even then, the water-soluble gum fraction will remain suspended rather than dissolved, requiring filtration if a clear extract is desired.
When working with oleo-gum-resins, the two-step process is essential: powder the material thoroughly, then macerate in the chosen solvent. For alcohol tinctures, the gum will dissolve along with the other components. For oil infusions, expect a cloudy extract that requires straining through fine muslin or coffee filters.
3. True Gums (Water-Soluble Only)
Pure gums contain no essential oils or resinous material. They consist entirely of water-soluble polysaccharides and will not dissolve in oils, fats, or alcohol under any circumstances. When mixed with water, they form thick, mucilaginous solutions used primarily as thickeners, emulsifiers, and demulcents rather than for aromatic properties.
Examples include:
- Gum Arabic (Acacia senegal) – Harvested from acacia trees in sub-Saharan Africa
- Gum Tragacanth (Astragalus gummifer) – From a thorny shrub native to the Middle East
- Indian Tragacanth (Sterculia urens) – Also called karaya gum
- Cherry and almond gum (Prunus species) – Often visible on stone fruit trees as translucent amber nodules
These materials have limited application in aromatic medicine but find use in herbal medicine as soothing agents for irritated mucous membranes and in natural product formulation as stabilizers and thickeners.
A Note on Sap vs. Exudates
It’s worth clarifying that resins, gums, and oleoresins differ fundamentally from sap. Sap flows through the vascular system of trees (xylem and phloem) to transport water and nutrients throughout the plant—a process called transpiration. Resins, by contrast, accumulate in specialized resin ducts within the bark and are expelled in response to injury. While sap sustains the tree’s daily metabolism, resinous exudates serve as emergency defense mechanisms against pathogens, water loss, and insect damage.
Sustainability Considerations
Many resin- and oleo-gum-resin-producing species face conservation challenges. The International Union for Conservation of Nature (IUCN) Red List includes numerous Boswellia species (frankincense), Commiphora species (myrrh), Canarium luzonicum (elemi), Copaifera paupera and C. glycycarpa (copaiba), and various Styrax species (benzoin).
Overharvesting, habitat destruction, and climate change threaten these aromatic treasures.
As aromatherapy practitioners and consumers, sourcing from suppliers who practice sustainable harvesting, support local communities, and document their supply chains represents both ethical responsibility and practical necessity—we cannot practice plant medicine if the plants themselves disappear.
