Determining whether Cannabis is a tree or a shrub requires examining its botanical classification rather than its visual appearance. Although the plant grows tall and develops a thick central stalk, the common name “weed” is misleading. To understand its true nature, we must examine the formal characteristics that define a tree and compare them to the life cycle and internal structure of the Cannabis plant.
Botanical Criteria for Defining a Tree
A tree is botanically defined by characteristics that allow it to attain great height and longevity. The primary criterion is the presence of a woody stem, or trunk, composed of true wood, known as secondary xylem. This wood provides the necessary strength and rigidity to support the plant against gravity and wind.
Trees are characterized by perennial growth, meaning they live for many years. This long lifespan is enabled by secondary growth, where the vascular cambium causes the trunk to grow in girth. This growth results in the formation of annual rings and protective bark. The growth habit involves a single, self-supporting trunk that branches only at a considerable height, distinguishing it from a multi-stemmed shrub.
Classification and Life Cycle of Cannabis
The Cannabis plant, in contrast to a tree, is botanically classified as an annual herbaceous plant. An annual plant completes its entire life cycle—from germinating seed to mature seed production and death—within a single growing season. This cycle typically lasts only four to ten months in the wild, which fundamentally prevents it from being a perennial tree.
This annual life cycle is the most significant factor differentiating Cannabis from perennial woody plants. Even varieties that exhibit a woody base lack the extended, multi-year lifespan necessary to form a true trunk. The plant is programmed to invest its energy into rapid growth and reproduction before seasonal changes end its existence. While growers can artificially extend the vegetative phase indoors, this manipulation does not change the plant’s inherent biological classification.
Structural Differences in Stem Composition
The stem of a Cannabis plant, often referred to as a stalk, may become thick and rigid, but its internal structure is not that of true wood. The stem contains two types of fibers: the long, flexible bast fibers in the outer phloem layer and the shorter, lignified hurd fibers in the inner xylem core. These fibers are the source of hemp’s industrial strength.
The tissue is lignified, meaning it contains lignin, a polymer that provides mechanical support. However, the process in Cannabis is limited compared to a tree. The lignification supports the plant’s single season of upright growth rather than building a permanent, ever-widening trunk. The inner core of the stem is characterized by a central pith, often hollow in mature plants, a trait common to many herbaceous species but rarely seen in a true tree trunk.
True wood formation relies on continuous secondary growth from the vascular cambium, which produces a solid cylinder of secondary xylem. In Cannabis, while a vascular cambium is present and produces some secondary xylem, this growth is limited to that single season. The stem’s composition confirms its classification as a large, stiff-stemmed herb, not a woody tree.