Smilax is a genus of approximately 300–350 species of perennial vines and shrubs in the greenbrier family, Smilacaceae, characterized by climbing or trailing stems that are often armed with prickles and supported by extensive tuberous rhizomes.[1] These plants typically feature alternate, entire leaves with reticulate venation and produce small, dioecious flowers in umbels, followed by berry-like fruits that attract wildlife.[2] Native primarily to tropical and subtropical regions worldwide, with extensions into temperate zones of North America, East Asia, and Europe, the genus exhibits a pantropical distribution and includes both woody-based and herbaceous forms.[3][4]Many species of Smilax are ecologically important as they provide food and cover for wildlife, including deer, birds, and small mammals that consume their berries and foliage, while their vigorous growth makes them common in forests, thickets, and disturbed areas.[5] However, their prickly stems and aggressive spreading via rhizomes often render them weedy or invasive in some habitats, complicating management in agriculture and forestry.[6] Economically and culturally, certain species, such as Smilax aristolochiifolia and Smilax glabra, have been utilized for centuries in traditional medicine; their rhizomes yield sarsaparilla, a flavoring agent in beverages and a source of steroidal saponins employed for anti-inflammatory, antioxidant, and antimicrobial properties.[7][4] In addition to medicinal applications, parts of some Smilax species serve as browse for livestock and have been used in folk remedies for skin conditions, infections, and rheumatism across various indigenous cultures.[5][8]
Taxonomy and Classification
Etymology and History
The genus name Smilax derives from the Ancient Greek word smīlax (σμῖλαξ), referring to bindweed or a twining plant, with uncertain origins possibly linked to an ancient name for evergreen trees such as Quercus ilex or Taxus baccata.[9] This nomenclature is tied to Greek mythology, where Smilax was a nymph whose unrequited love for the mortal youth Crocus led the gods to transform her into the bindweed plant, as recounted in Ovid's Metamorphoses and Pliny the Elder's Natural History.[10]In ancient botanical and medicinal literature, Smilax species were recognized for their therapeutic properties, notably in Pedanius Dioscorides' De Materia Medica (circa 50–70 CE), where rough bindweed (Smilax aspera) is described in Book 4, Chapter 144 as an antidote to poisons and a remedy for various ailments, reflecting its early use in Mediterranean herbal traditions.[11]During the Age of Exploration, European accounts of New World Smilax species, particularly sarsaparilla varieties like Smilax ornata and Smilax aristolochiifolia, highlighted their medicinal value; Spanish explorers introduced these roots to Europe around 1545, praising them as treatments for syphilis and skin conditions in chronicles such as those by Pedro Cieza de León in 1540.[12][13]The formal binomial classification of Smilax evolved with Carl Linnaeus' Species Plantarum in 1753, where Smilax aspera was designated the type species, establishing the genus within modern taxonomy based on specimens from European habitats.[14]
Phylogenetic Relationships
Smilax is the type genus and sole member of the family Smilacaceae, placed within the order Liliales in the monocotyledons. The genus encompasses approximately 270 species of primarily dioecious, climbing vines or shrubs distributed across tropical and temperate regions worldwide.[15][16][17]The type species is Smilax aspera L., a prickly climber native to the Mediterranean, Africa, and Asia. Several historical names have been recognized as synonyms of Smilax, including Nemexia Raf. and Parillax Raf., which were proposed for herbaceous or specific sectional groups but are now subsumed under the genus.[18][19]Molecular phylogenetic studies have clarified the evolutionary relationships within Smilax, revealing it as monophyletic despite earlier uncertainties. A key 2013 analysis using nuclear and plastid DNA sequences identified four major clades (A–D) supported by biogeographic patterns: Clade A includes S. aspera and relatives with a tri-continental distribution across the Old World; Clade B comprises mostly New World (American) species; Clade C features prickleless, herbaceous taxa primarily in Asia, incorporating the former genus Heterosmilax; and Clade D consists of woody Old World species in Asia, Africa, and Australia. This study also demonstrated that Heterosmilax is nested within Smilax, supporting its reduction to sectional status and resolving debates on genus boundaries. Subsequent studies, including chloroplast genome analyses as of 2023, continue to support the monophyly and clade structure of Smilax.[20][21][22]However, traditional infrageneric sections, such as Smilax and Riparia, exhibit polyphyly, with species distributed across multiple clades rather than forming cohesive groups. This non-monophyly of sections, confirmed by both morphological and molecular data, underscores the need for revised classifications based on phylogenetic evidence rather than solely on vegetative or reproductive traits.[23][24]
List of Selected Species
The genus Smilax includes approximately 270 species distributed primarily in tropical and subtropical regions worldwide, with significant diversity in the Americas and Asia; for instance, China hosts approximately 80 species, around 40 of which are endemic (as of 2023).[25][17][26] Below is a curated selection of 18 notable species, grouped by major geographic clades for context, highlighting representatives with recognized common names, native ranges, and brief identifiers of significance.
American Species
These species predominantly belong to clades adapted to temperate and subtropical forests of the New World.
Smilax rotundifolia L.: Common greenbrier; native to eastern North America (from Ontario to Florida and Texas).[17]
Smilax glauca Walter: Catbrier or saw greenbrier; native to southeastern United States (Virginia to Florida and Texas).
Smilax herbacea L.: Smooth carrionflower; native to central and eastern North America (Nova Scotia to Georgia and Texas).[27]
Smilax laurifolia L.: Laurel greenbrier or bamboo vine; native to southeastern United States (Delaware to Florida and Texas).[17]
Smilax aristolochiifolia Mill.: Gray sarsaparilla; native to central and northeastern Mexico.[28]
Smilax ornata Lem.: Jamaican sarsaparilla; native to Central America (Mexico to Honduras) and the Caribbean.[29]
Smilax campestris Griseb.: Zarzaparrilla; native to southern South America (Brazil, Paraguay, Argentina).[17]
Smilax domingensis (Willd.) Kunth: Honduras sarsaparilla; native to Mexico, Central America, and the Caribbean.[30]
Asian Species
Asian clades show high endemism, particularly in China and Southeast Asia, often linked to medicinal traditions.
Smilax glabra Roxb.: Tu fu ling; native to southern China and Southeast Asia (India to Indonesia).[25]
Smilax china L.: China root; native to eastern Asia (China to Japan and the Philippines).[31]
Smilax japonica A.DC.: Japanese greenbrier; native to eastern Asia (Japan, Korea, Russia).[17]
Smilax riparia Loes.: Streambank smilax; native to central and southern China (endemic).[25]
Smilax sieboldii Miq.: Siebold's smilax; native to eastern Asia (China, Japan, Korea).[25]
Smilax zeylanica L.: Sri Lanka smilax; native to South Asia (India, Sri Lanka, Myanmar).[17]
Old World Species (Europe, Africa, and Oceania)
These represent clades in the Paleotropics and Mediterranean, with some island endemism.
Smilax aspera L.: Rough bindweed or common smilax; native to the Mediterranean Basin, southern Europe, and North Africa.[17]
Smilax mauritiana DC.: Mauritius smilax; native to the Mascarene Islands (Mauritius, Madagascar; endemic to Indian Ocean region).[17]
Smilax anceps Baker: African smilax; native to tropical Africa (Ethiopia to South Africa).[17]
Smilax australis R.Br.: Austral sarsparilla; native to eastern Australia and Lord Howe Island.[17]
Botanical Characteristics
Morphology
Smilax species are woody or herbaceous vines or shrubs capable of reaching lengths of 10-20 meters, with cylindrical, wiry stems that are often armed with prickles, though some taxa exhibit unarmed growth. These plants are dioecious, bearing separate male and female individuals, and typically climb via paired tendrils arising from the petiole apex.[32][33]Leaves are alternate and simple, exhibiting reticulate venation with prominent parallel primary veins; they vary from heart-shaped (cordate) to ovate or lanceolate, measuring 4-30 cm long and 3-15 cm wide, with leathery to papery textures. Foliage is evergreen in many tropical and subtropical species or deciduous in temperate ones, and some leaves display a glaucous, waxy underside for protection against herbivory or desiccation.[32][34]Flowers are small, 3-6 mm across, with greenish-white tepals and borne in axillary umbels on slender peduncles; male flowers feature six stamens, while female ones have three stigmas. The resulting fruits are globose berries, 5-10 mm in diameter, maturing from green to red or black and containing 1-3 seeds per berry.[35][34]Morphological variations are evident across the genus; for instance, Smilax rotundifolia produces stout, densely prickled stems and round-ovate leaves 4-13 cm long with glossy surfaces, whereas Smilax glabra has smooth, glabrous stems up to 6 m long and broadly ovate leaves 7-15 cm long with cordate bases.[35][36][34]
Reproduction and Growth
Smilax species exhibit dioecious sexual reproduction, with male and female flowers occurring on separate individuals. In species such as Smilax herbacea, male plants produce larger inflorescences with twice as many umbels and approximately 68% more flowers than female plants, facilitating higher pollen output. The small, greenish-yellow flowers are primarily insect-pollinated, with pollen grains often connected by viscin threads that promote adhesion to insect bodies rather than wind dispersal.[37][27][38]Following pollination, female plants develop berries containing one to several seeds, which are primarily dispersed by birds attracted to the fleshy fruits. Seed germination in Smilax requires scarification to overcome dormancy, often achieved naturally through passage via bird digestive tracts, and thrives under moist conditions at temperatures around 20-30°C. Germination typically occurs after 1-3 months, with rates varying by species from 19% to 79%, and seedlings initially producing cataphylls before developing true leaves.[39][40][41]Asexual reproduction occurs predominantly through rhizomes and root sprouting, allowing clonal colony formation and persistence in disturbed habitats. Rhizomes, which are woody and tuberous, enable vegetative propagation by producing new shoots from underground stems, contributing to the plant's invasive potential in some regions. In optimal conditions, such as nutrient-rich soils and adequate moisture, Smilax vines can achieve growth rates of up to 1 m per year, with stems extending via tendrils to climb supports.[27][42]As perennial plants, Smilax species maintain long-term survival through persistent rhizomes that store nutrients and support regrowth each season. In temperate regions, above-ground parts of herbaceous species like S. herbacea enter winter dormancy, dying back while rhizomes remain viable underground, resuming growth in spring; woody species in warmer climates remain evergreen. This lifecycle supports multi-year fruit production and colony expansion.[43][37]
Distribution and Habitat
Geographic Range
The genus Smilax displays a pantropical distribution, with extensions into temperate zones worldwide. It is native across the Americas, encompassing approximately 20 species in North America north of Mexico and 29 species in Central America and the Caribbean. In Asia, diversity is highest, with roughly 80–90 species recorded in China, contributing to the genus's overall estimate of approximately 300 species globally (with 267 accepted per POWO as of 2025). Native occurrences also extend to Africa, where about two species are present, and to Oceania, including several Australian endemics such as S. australis.[9][44][45][32][17][46]Certain species have been introduced beyond their native ranges and established in new regions. For instance, S. rotundifolia, originally from eastern North America, has naturalized in parts of Europe, including Belgium, where it persists as a locally invasive escape from cultivation in woodlands.[47]Biogeographic patterns in Smilax align with phylogenetic clades, where Clade B predominantly includes American species and Clade D encompasses mostly Asian ones, reflecting historical dispersals across continents such as via the Bering land bridge during the Pleistocene. A Gondwanan origin for the genus has been hypothesized based on these disjunct distributions and fossil evidence from the Miocene suggesting ancient intercontinental connections.[32][48]
Environmental Preferences
Smilax species thrive in moist, well-drained soils rich in organic matter and of moderate fertility, typically with an optimum pH between 5.0 and 6.0. These conditions are commonly found in woodlands, forest edges, and disturbed areas, where the plants can establish extensive root systems.[39][27]The genus exhibits broad climatic tolerances, ranging from subtropical to temperate zones, with certain species adapting to arid margins through physiological resilience. Elevations vary widely, from sea level to as high as 3000 m in montane forests of the Andes, allowing occupation of diverse abiotic niches within these climates.[27]Smilax plants tolerate partial shade to full sun but perform best in intermediate light levels, such as 10-20% shade, and show strong drought tolerance once established via deep rhizomes and roots that access subsurface moisture. They require consistent moisture during early growth but can persist in subxeric to xeric sites thereafter.[39][49]
Ecology and Interactions
Wildlife Interactions
Smilax species engage in mutualistic relationships with various insects for pollination, primarily through entomophilous mechanisms. Flowers of many Smilax, such as S. herbacea, emit a carrion-like odor that attracts pollinators including bees, flies, and beetles, which transfer pollen while foraging for resources like nectar or pollen grains.[50] In S. herbacea, halictid and andrenid bees, along with flies, serve as primary pollinators by collecting pollen for brood provisioning, facilitating cross-pollination in clustered umbels.[51]Several Smilax species act as host plants for Lepidoptera larvae, providing foliage for development while potentially facing herbivory pressure. For instance, S. perfoliata and S. zeylanica support larvae of the blue admiral butterfly (Kaniska canace) in Asia, where caterpillars feed on leaves before pupation.[52] Other species, such as S. aspera, host larvae of the common leopard (Phalanta phalantha) and skippers like Tagiades litigiosa, contributing to biodiversity in tropical and subtropical regions.[53] These interactions can be antagonistic for the plant, as larval feeding damages foliage, though Smilax's thorns on stems help deter larger browsing insects and vertebrates.The berries of Smilax serve as a food source for birds and some mammals, promoting seed dispersal while exhibiting chemical defenses against excessive herbivory. Fruits of species like S. rotundifolia and S. herbacea are consumed by songbirds (e.g., northern cardinals, white-throated sparrows), ruffed grouse, and wild turkeys, with birds excreting viable seeds that aid long-distance dispersal.[39][43] Mammals such as white-tailed deer browse foliage and tender shoots of S. bona-nox and S. rotundifolia, though thorns on the vines provide physical protection against heavy browsing by deer and rabbits.[54][55] Additionally, saponins in Smilax tissues impart toxicity, deterring overconsumption by herbivores and reducing palatability for sensitive species.[4][56]
Ecological Role and Invasiveness
Smilax species play a significant role in native forest ecosystems by forming dense thickets that provide protective cover for birds and small mammals, such as white-tailed deer and various songbirds.[39] These thickets also contribute to erosion control through their vigorous growth and extensive tuberous rhizomes, which stabilize soil in disturbed or rehabilitated areas, including rights-of-way and wetland margins.[57] In understory layers, Smilax vines act as structural stabilizers, enhancing habitat complexity and supporting overall biodiversity by facilitating seed dispersal via fruits consumed by wildlife.[39]Several Smilax species, including S. rotundifolia, exhibit invasive tendencies by forming impenetrable thickets that dominate early successional stages on disturbed sites, outcompeting native vegetation and inhibiting tree seedling regeneration in forests of the southeastern United States.[39] As a silvicultural pest, S. laurifolia similarly climbs and weighs down young trees, reducing forest productivity in lowland and coastal habitats.[57] Management typically involves repeated cutting to exhaust root reserves or application of herbicides like glyphosate, though these vines' resilience to disturbance often requires integrated approaches for long-term control.[58]Conservation implications for Smilax vary across species; while some, like S. rotundifolia, are threatened in northern regions such as Canada due to habitat loss from urbanization and fragmentation, others are weedy and widespread in their native ranges.[59] These plants contribute to biodiversity as resilient understory components, but their aggressive growth in altered ecosystems can exacerbate challenges in maintaining native plant diversity.[39]
Human Uses and Cultivation
Culinary and Traditional Uses
The roots of Smilax ornata and Smilax aristolochiifolia have been harvested for centuries to produce sarsaparilla, a non-alcoholic beverage flavored with the root bark's aromatic compounds, evoking a root beer-like taste.[60] This drink gained widespread popularity in the 19th-century United States, where it was marketed as a refreshing tonic and featured in sodas, often combined with ingredients like sassafras and wintergreen for enhanced flavor.[61] In Mexico and Central America, S. aristolochiifolia roots continue to be used in similar beverages, confectionery, and bakery products due to their bitter, licorice-like profile.[62]Young shoots and leaves of various Smilax species are edible and have been incorporated into diets across regions, particularly in Asia and the Americas. In East Asia, the tender shoots and leaves of Smilax china are consumed raw in salads or cooked as a potherb, similar to spinach, providing a mild vegetable option in spring foraging.[63] In the Americas, including North American woodlands, the young shoots of species like Smilax rotundifolia are harvested for their asparagus-like texture and eaten raw or boiled, while leaves serve as a cooked green in soups or stews.[64] The berries, which ripen to red or black, can be used in jams or jellies after cooking, though they are often unpalatable raw due to low flesh content and potential mild stomach irritation from natural saponins; consumption should be limited to avoid digestive upset.[64]Smilax species hold traditional significance in Indigenous diets and cultural practices, especially among Native American tribes in the southeastern United States. The Creek, Yamassee, and Cherokee peoples utilized the roots as a starch source for thickening soups and stews, and prepared flavored drinks from powdered red root extracts, integrating the plant into daily sustenance.[64] In broader folklore, Smilax vines symbolize binding and entanglement, drawing from Greek mythology where the nymph Smilax was transformed into a twining bindweed after a tragic love story; the plant's thorny vines were woven into garlands for Dionysian rituals, representing ecstatic union and boundary reestablishment in ceremonies.[10]
Medicinal Applications
Smilax glabra, known as tu fu ling in traditional Chinese medicine (TCM), has been utilized for centuries to treat conditions such as syphilis and for detoxification purposes. Historical records indicate its application in combination therapies, including with penicillin, for managing syphilis serum resistance, with observed curative effects in clinical observations. The rhizome is valued for its detoxifying properties, attributed to bioactive proteins like smilaxin, which contribute to antipyretic and diuretic actions in TCM formulations.[34][65]Another key species, Smilax ornata (commonly referred to as Jamaican sarsaparilla), has been traditionally employed to alleviate rheumatism and various skin conditions, including psoriasis and dermatitis. Extracts from S. ornata have demonstrated significant anti-inflammatory and analgesic effects in preclinical studies, such as reduced paw edema in animal models of inflammation, supporting its historical use for rheumatic disorders. For skin ailments, its inclusion in herbal mixtures has shown potential in reducing swelling and pain associated with psoriatic arthritis, though human clinical data remains limited.[66][67]The pharmacological potential of Smilax species stems from active compounds like diosgenin, a steroidal sapogenin serving as a precursor for hormone synthesis; parillin, a glycoside of sarsasapogenin; and sarsasapogenin itself, which exhibits anti-inflammatory effects by reducing oxidative stress and inhibiting TNF-α. Modern studies have confirmed anti-inflammatory activities through inhibition of cyclooxygenase-2 (COX-2) and diuretic properties via enhanced renal function in experimental models. These compounds contribute to the plant's studied effects on immunity modulation and liver protection.[4][68]While historical uses persist, current evidence highlights limitations, with the U.S. Food and Drug Administration (FDA) regulating sarsaparilla under dietary supplements, prohibiting unsubstantiated disease treatment claims due to insufficient clinical proof for conditions like syphilis or rheumatism. Recent clinical trials, particularly on Smilax china in the 2020s, have focused on its antioxidant properties; for instance, polysaccharides from S. china alleviated oxidative stress-induced liver damage in acetaminophen-exposed models by activating the Nrf2-ARE pathway, demonstrating hepatoprotective potential. Ethanol extracts of S. china rhizomes also varied in antioxidant capacity across regions, with phenolic content correlating to free radical scavenging efficacy.[69][70][71]
Cultivation and Conservation
Smilax species can be propagated vegetatively through rhizome division or by seeds, with the latter requiring exposure to light for optimal germination and remaining viable for several years when stored under cool, dry conditions. Rhizomes, which are extensive and knobby, allow for easy cloning but demand careful handling to avoid damage during transplanting. These plants thrive in well-drained, acidic soils with a pH of 5.0 to 6.0, tolerating a range of moisture levels from moist to occasionally dry conditions, and perform best in full sun to partial shade. Hardy in USDA zones 6 to 10, they are adaptable to various sites including woodlands and edges, making them suitable for ornamental landscaping where they form dense hedges or groundcovers due to their climbing, thorny habits.[39][72][58][33]Commercial production of Smilax primarily targets species such as S. ornata (sarsaparilla) for harvesting roots used in herbal extracts and traditional beverages like root beer, driven by growing demand for natural health products in markets projected to expand significantly. Cultivation faces challenges including the plant's slow growth as a perennial vine, which delays harvest times, and its dioecious nature, requiring intentional planting of both male and female individuals to ensure fruit and seed production for propagation or breeding. These factors contribute to reliance on wild harvesting in some regions, complicating sustainable scaling.[73][74][75][76]Few Smilax species have been formally assessed by the IUCN Red List, with those evaluated, such as Smilax aspera in Europe, generally listed as Least Concern due to their wide distributions. However, some endemic species face higher risks; for instance, S. nageliana has been assessed as Critically Endangered in regional studies.[77][78] Primary threats include deforestation for agriculture and urban expansion, alongside overharvesting of rhizomes for medicinal and commercial uses, particularly in tropical habitats. Conservation measures emphasize protection within biodiversity hotspots, such as Caribbean and Andean forests, where species occur in national parks and reserves to mitigate habitat fragmentation and promote sustainable harvesting practices.[79][80]