Why Does Resin Differ Between Two Trees? The Causes of Oud's Variation

If you were to place two adjacent pieces of oud from two different trees — indeed sometimes from a single forest — you would find them differing in color, density, and scent. So why does resin differ from one tree to another, even when they are of the same species and grow in the same soil? This article — one of the axes of the guide to the science of oud formation — answers precisely this question: not why some trees produce oud and others do not, but why the resin of the producing trees varies one from another. We will survey the factors believed to be behind this variation — the individual differences between trees, the type of injury and its duration, the microbial interaction, and the micro-environment and time — while clearly distinguishing between what knowledge points to and what remains a subject of research.

1. No two trees are identical

Before we ask why the resin differs, we ought to settle on a primary fact: oud is a natural, non-homogeneous material, and it is not to be expected in the first place to be uniform. For even two adjacent trees of the same species, which grew in the same soil and were exposed to the same climate, may produce oud that differs in its grade, its scent, and its density. This variation is not a defect in the oud nor a flaw in its formation, but a natural consequence of its being the outcome of a complex biological process in which many factors intersect.

It is worth here distinguishing our question from one close to it and different from it. The matter of "why some trees produce oud and others do not" — that is, why one tree responds to harm by depositing resin while another does not respond at all — we treated in why some trees produce oud. As for what we examine here, it is the next step: among the trees that do produce oud, why does what they produce differ one from another? The first question is about the origin of production, and this is about its variation.

The general framework within which we work is simple in its principle: since oud is a defensive response that the tree creates in the face of harm, every factor that influences this response — from the nature of the tree itself, to the type of harm, to what enters of the microorganisms, to its surroundings and the time it takes — can leave its imprint on the resulting resin. And because these factors vary from one tree to another, the resin varies accordingly. We will take them one by one, beginning with the tree itself.

2. The first factor: individual differences

The first thing that explains the variation is that trees — like the rest of living beings — are individuals, not copies. Each tree has its own constitution, its state of health, and its degree of vitality, and these are individual differences believed to be reflected in its capacity to form resin and in the character of what it forms. A strong, healthy tree may respond to harm with a response that differs from that of a weaker or older or more strained tree, even if the conditions around them are similar.

Age and vitality have a role that is likely to be influential: the older tree that has lived longer may have undergone of infections and accumulated of responses what a young tree has not undergone, so the depth of its resin differs. But we are reserved about making this an automatic rule; for age raises the probability and does not guarantee a result, and a younger tree in favorable conditions may produce resin richer than another older one that grew in poorer conditions.

Honesty is indispensable when speaking of genetics in particular. It is reasonable that the genetic makeup of the tree has an effect on its inclination to form resin and on its character, for individual differences are in part genetic by nature. But the precise map of this effect — which genetic factors do exactly what — has not yet been fully drawn, and it remains a subject of research. We therefore content ourselves with saying that the individual differences between trees are a real factor in the variation, without claiming detailed knowledge of their genetic mechanisms.

3. The type of injury and its duration

If oud is a response to harm, then it is natural for it to differ with the difference of the harm itself. Wounds are not of one kind: the breaking of a branch in a storm differs from a split in the bark, and a small hole made by an insect differs from wide, extended damage. Each of these injuries opens a different door before the external factors, and calls forth a response that may vary in its amount and its site. We detailed how a wound is a first trigger in the role of wounds in resin formation.

No less important than the type of injury is the time of the injury. A tree injured early, which kept accumulating its resin for long years, differs from another recently injured, upon whose harm only a little has passed. Likewise, trees vary in the number of injuries: one tree may be subjected to a single harm in its lifetime, and another to repeated injuries in various sites, so its resin is distributed and varies accordingly.

It is useful to recall a principle we treated in the relationship between damage and resin: that the relationship between the amount of harm and its type and the resulting resin is a complex relationship not reduced to a simple arithmetic rule. It is not true that greater harm always produces more resin; for the matter depends on the response of the tree, its capacity, and its conditions. What matters here is that the diversity of injuries — in type, duration, repetition, and site — is one of the clearest causes of the difference of one tree's resin from another's, even between two trees similar in all else.

4. The microbial interaction

When the wound is opened, the matter does not remain between the tree and the harm alone; for microorganisms enter into the equation. It is widely held that fungi and microbial organisms play a role in triggering the tree's response and depositing the resin, and we surveyed this role — with the debate that surrounds it — in the role of fungi in oud formation. And because what enters of these organisms and how it interacts with the tree may differ from one case to another, it is reasonable that this interaction is one of the sources of variation between trees.

Among what is researched in this context is what is known as internal infections (endophytes): microorganisms that live within the plant's tissues, and it is studied whether they contribute — when conditions change after the injury — to shaping the response. And because the community of these organisms may vary from one tree to another, it is believed that its difference may be reflected in the difference of the resin. But all of this is a research direction not yet settled, so we present it as a studied possibility, not an established fact.

Here we repeat a caution we abide by: the role of microorganisms in the formation of oud is still a subject of research and debate, and it is not valid to assert that a particular organism is the one that "makes" the difference between one tree and another. The more accurate statement is that the microbial interaction is part of an intertwined system that includes the wound, the tree, the time, and the environment, and that the difference of this interaction — as one of the threads of the system — may contribute to the variation we observe. As for detailing "how" exactly, that is among what has not yet had its doors closed.

5. The micro-environment and time

There is a finer layer of "environment" that ought to be noted. When we say that two trees grew in "the same place," we mean the large surroundings; but each tree has its own micro-environment: its position of shade or sun, its share of moisture and drainage, and the organisms surrounding its trunk. These small differences in the immediate surroundings are believed to contribute — with the passage of time — to the difference in the course of formation and its result between a tree and its neighbor.

Intersecting with the micro-environment is the factor of time. The accumulation of resin is a slow process that extends over years and perhaps decades, and we detailed its dynamics in how many years resin formation takes. And since trees differ in when their formation began and how long it continued, the difference in duration alone is enough to make one tree's resin deeper or denser than another's. Time here is not a mere backdrop, but an active factor in the variation.

Above the micro-environment and time comes a broader layer, which is the effect of the region and origin on the character of the oud and its scent, to which we devoted the effect of region on oud scent. Yet the relationship between the two layers deserves precision: the effect of region shapes the general expectation of the character of an oud, but it does not abolish the variation within a single region. For even in the same origin, the individual differences, the injuries, and the micro-environments continue to do their work, so oud varies from one tree to another within the same territory. The origin draws the broad features, and the individual factors carve the details.

6. Why this makes oud unique

When we gather these factors — the individual differences, the type of injury and its duration, the microbial interaction, and the micro-environment and time — we arrive at a conclusion beautiful in its essence: there are no two pieces of oud completely identical. Each piece is the outcome of a unique history of harm, response, and accumulation that has not been repeated in its exact details in another tree. Oud, in this sense, is closer to a fingerprint than to a product cast in a mold.

It is important to see this variation as it truly is: not a deficiency nor a flaw, but an authentic trait. Natural, non-homogeneous materials vary by their nature, just as two fruits from a single tree are not identical, nor two coffee beans from a single season. Whoever expects of oud a complete, identical industrial uniformity misunderstands its nature; for the uniqueness of each piece is the very thing that makes oud a living material with a personality, not a repeated commodity.

This uniqueness is also what makes the experience of oud enjoyable for its people: that each piece has its tale in color, weight, and scent upon heating, and that the discovery of its unique character is part of its pleasure. The variation that may at first glance seem a "problem of consistency" is in truth the source of oud's richness and its inexhaustible diversity.

7. What this means for the buyer

The most important practical lesson from all that precedes: that the truest judgment on oud is upon the piece itself, not upon its category or its name. Since the variation exists even within a single species and a single origin, knowing that an oud is "from such a region" or "of such a species" draws a general expectation but does not dispense with testing the piece in your hands. The category points you to the direction, and direct experience is what decides.

From here springs the value of experience before acquisition. When oud varies from one piece to another, smelling the scent upon heating, and feeling the density and the weight, becomes a truer guide than any written description. We detailed the practical criteria of selection in how to choose authentic Indonesian oud; and its conclusion is that you judge with your senses what is before you, not a general category whose individuals may vary.

This is why we encourage at Oud Treasure beginning with a sample when that is possible; for the sample allows you to test the actual character of the oud you are considering, instead of buying on the basis of a name or an image. This is an extension of a principle we abide by: we describe the oud as it is, and we leave it to experience to complete what description is unable to convey. The variation of oud is not an obstacle before conscious buying, but an invitation for the buying to be founded on experience, not on assumption.