The genus Smilax, commonly known as Greenbrier or Catbrier, includes hundreds of species of perennial, often thorny, climbing vines found across temperate and tropical regions worldwide. While the above-ground stems are easily recognized by their tenacious, woody growth, the plant’s true persistence lies beneath the soil surface. This subterranean system is responsible for the plant’s remarkable ability to colonize and resist removal, and it is the source of its historical fame as Sarsaparilla. This hidden network reveals a complex structure that serves multiple functions, from long-term survival to vegetative reproduction.
Anatomical Structure and Identification
The subterranean system of Smilax is not a single, simple root but a complex arrangement of specialized underground stems and storage organs. This network is primarily composed of rhizomes, which are horizontal stems that grow beneath the soil surface. These rhizomes are typically unthickened and somewhat straight, featuring distinct, swollen nodes where new growth can emerge.
Interspersed within this network are specialized storage tubers, sometimes referred to as root crowns or tuberosities. These organs function as the plant’s main reserve bank, appearing rounded, lumpy, and filled with dense, starchy material. These underground parts are often dark or reddish-brown, sometimes with a lighter, knobby interior.
The rhizomes and tubers differ significantly from the plant’s thinner, fibrous roots, which primarily serve to absorb water and nutrients. In some species, a particularly dense and hard tuberosity forms from the primordial node of the seedling, acting as a central anchor. This structure is a defining physical characteristic that sets the Smilax genus apart from other climbing vines.
Primary Functions Storage and Survival
The primary purpose of the specialized Smilax root system is the long-term storage of energy reserves and water. The large, starchy tubers are densely packed with carbohydrates, primarily starches. This stored energy fuels the plant’s growth, especially when above-ground resources are scarce.
These subterranean reserves are crucial for the plant’s perennial life cycle and survival. By storing significant resources underground, the plant can effectively survive environmental stresses like deep winter freezes, prolonged drought, or complete destruction of its aerial stems.
When the above-ground vine is damaged, such as by fire or cutting, the stored energy allows the underground system to rapidly regenerate new shoots. Experiments often show that cutting the aerial growth back forces the plant to maximize the energy stored in the root system for the next growth cycle. This physiological mechanism ensures the plant’s survival year after year, regardless of seasonal or human interference.
Propagation and Growth Dynamics
The extensive rhizome network drives the plant’s vigorous vegetative reproduction and contributes to its reputation for tenacity. New aerial shoots, or canes, do not rely solely on seeds but emerge directly from the numerous nodes along the horizontal rhizomes. This process allows the plant to spread laterally, creating dense clusters of vines from a single original plant.
This vegetative spread is facilitated by “runners,” which are elongated, thin rhizomes that extend the plant’s reach beneath the soil. As these runners grow, they establish new growth points, allowing the plant to colonize large areas over time. The result is often a dense thicket of vines, with multiple stems arising from the ground in the same small area.
The plant’s persistence is directly related to the difficulty of separating the aerial stem from its underground lifeline. Simply cutting the vine above the soil is ineffective because viable rhizomes and tubers remain in place, ready to sprout new growth. Successful removal requires extracting the entire subterranean system, which can be extensive and deeply rooted, underscoring the effectiveness of this growth dynamic.
Traditional and Modern Uses of the Rhizome
Beyond its ecological role, the rhizome of several Smilax species has a long history of human use, particularly those known as Sarsaparilla. Traditionally, the dried and processed roots were utilized as a tonic and a purported “blood purifier” in folk medicine across the Americas and Asia. Specific species like Smilax glabra were used to treat skin conditions, infections, and rheumatism.
Chemical Composition and Food Use
In modern applications, the rhizomes are prized primarily for their chemical compounds, notably saponins. These compounds contribute to the plant’s reported anti-inflammatory and antioxidant properties. Saponins are also utilized in the food industry for their foaming action. Historically, extracts from the root were a primary ingredient in the original sarsaparilla and root beer beverages.
Current Research
Today, the harvested material is still used in functional foods and supplements. However, scientific validation for many traditional medicinal claims is still developing. The complex chemical profile of the rhizome continues to be studied for its potential in areas ranging from anti-cancer research to cardiovascular protection.