The plant genus Lonicera, commonly known as honeysuckle, is often a source of confusion because of its varied appearance. Honeysuckle is not botanically classified as a true tree. The species are categorized either as woody, multi-stemmed shrubs or as climbing, twining vines. This dual nature explains why people often mistake large specimens for small trees, but they lack the structural characteristics that define an arborescent plant.
Defining a Tree Versus a Shrub or Vine
The categorization of a plant as a tree, shrub, or vine depends on its structural growth pattern. A true tree is defined by its ability to generate a single, erect, self-supporting woody stem, known as a trunk, that typically reaches a significant height. This structural integrity is achieved through extensive secondary growth, producing substantial wood (secondary xylem) for strength. A shrub is a woody plant that produces multiple stems arising directly from the base and lacks the single, dominant trunk structure of a tree. Vines are characterized by flexible, highly elongated stems and a lack of self-support, requiring external structures to climb vertically.
The Two Primary Growth Habits of Honeysuckle
The genus Lonicera contains approximately 180 species, manifesting primarily as either a sprawling vine or an upright shrub. Climbing varieties, such as Japanese honeysuckle (L. japonica), utilize flexible stems that coil or twine around supports. These vines lack the rigidity to stand on their own and can reach lengths of 15 to 20 feet when provided with vertical structures.
The shrub honeysuckles are woody bushes characterized by a dense, bushy growth habit and multiple arching stems emerging from the ground. Species like Amur honeysuckle (L. maackii) and Tartarian honeysuckle (L. tatarica) fall into this category. These shrubs can grow to impressive heights, often reaching between 6 and 20 feet, which contributes to the visual confusion with small trees.
Structural Differences in Large, Woody Honeysuckle
Large shrub honeysuckles, which can reach heights of nearly 20 feet, often cause observers to question their classification. However, the wood structure of even the oldest specimens reveals why they are not trees. Instead of a single, central trunk, these plants feature several main stems originating at or just above the soil line, resulting in a multi-stemmed base.
The internal anatomy of the stem provides a definitive difference from a tree trunk. Many invasive shrub honeysuckles possess a hollow or spongy pith in their older, woody stems. In contrast, a true tree trunk is composed of solid wood (secondary xylem) throughout its core. This lack of a solid wood column means the plant cannot achieve the structural integrity or height of a tree.