The phenomenon of trees containing deep red pigments within their structure is an outcome of specific biochemical processes. While the outer layer of a tree—the bark and the living sapwood—appears pale, the inner core, known as the heartwood, often reveals these dramatic colors. This coloration is a characteristic feature of many tree species and is intrinsically linked to the wood’s durability. The vibrant internal hue is a biological signature of a tree’s defense and maturation over decades.
The Chemistry Behind the Color
The deep colors found in heartwood are caused by the accumulation of secondary metabolites, which are non-structural chemical compounds produced by the tree. These compounds are collectively referred to as extractives because they can be chemically extracted from the wood tissue. The primary chemical groups responsible for the red spectrum are polyphenols, including various tannins and flavonoids.
As a tree ages, the living cells in the center of the trunk die and transform the soft, water-conducting sapwood into the hard, structural heartwood. During this transition, the tree deposits these extractives into the heartwood cells, effectively sealing them off. The concentration of these dense, colored compounds provides the wood with natural resistance to decay fungi and insects, which is why red woods are often highly durable.
Trees Known for Deep Red Heartwood
Several prized timber species are known globally for their profoundly red interior wood, which ranges from bright scarlet to deep purple-red. African Padauk (Pterocarpus spp.) is famous for its initially vibrant, reddish-orange heartwood. This coloration is not static; when exposed to light, the wood gradually oxidizes and darkens to a rich reddish-brown or purplish-brown over time.
Another notable example is Bloodwood (Brosimum rubescens), a dense tropical hardwood whose heartwood is a striking, vivid red that gives the species its common name. This intense color also tends to deepen into a darker, more subdued crimson-brown with age. Similarly, the heartwood of the Brazilwood tree (Paubrasilia echinata) contains the red dye precursor brazilin, which oxidizes to the vivid red pigment brazilein. This concentration of chemical extractives is what often gives these woods their exceptional hardness and resistance to rot and pests.
Red Inner Bark or Sap Production
The red color in some trees is produced as a liquid response to injury, distinguishing it from the heartwood phenomenon. This “bleeding” is a defense mechanism where the tree exuded a red resin or sap to seal wounds and ward off pathogens. The Dragon’s Blood Tree (Dracaena cinnabari) is perhaps the most famous example, found on the island of Socotra.
When the bark is cut or damaged, the tree releases a dark red sap that quickly dries into a resin known historically as “dragon’s blood.” The color is located in this resinous exudate and is not a permanent feature of the lumber itself. Many Australian eucalypts, often called “bloodwood” eucalypts, also produce a dark red exudate called kino when their trunks are damaged. This kino is rich in tannin compounds and solidifies into an amber-like material, serving to protect the tree from infection.
Practical Applications of Red Wood
The combination of striking color and natural durability makes red heartwoods highly sought after for specialized commercial and artistic applications. The high density and resonance of certain red woods, like Padauk and Brazilwood, make them valued materials in the construction of musical instruments. Brazilwood, for instance, is the traditional wood for crafting high-quality violin bows.
The inherent resistance to decay and insects provided by the colored extractives lends these woods to high-end construction, such as flooring, cabinetry, and outdoor furniture. Historically, some of these woods were prized for their color and used as natural dyes. The deep color and fine texture of woods like Bloodwood also make them ideal for decorative inlays, veneers, and small, turned objects.