The Smilax vine, commonly known as Greenbrier or Catbrier, is a genus of perennial woody vines recognized for its robust, clambering growth habit. It is often sought for its dense, evergreen foliage and the structure it provides, sometimes used ornamentally on trellises and porches. Smilax also has edible components, including tender young shoots and starchy roots, depending on the species. Cultivating this plant requires a practical approach because of its extreme vigor and aggressive spreading, making site selection and long-term control essential.
Identifying Smilax Needs and Selecting the Site
Selecting the correct site for a Smilax vine is the most important step for successful growth and management. The plant is remarkably adaptable, tolerating conditions from full sun to deep shade. It thrives best in the dappled light found on woodland edges or in areas with afternoon shade. Most native species are well-suited to USDA Hardiness Zones 6 through 9, demonstrating wide tolerance for different climate conditions.
The vine is not particular about soil composition, growing well in moist, loamy soils, dry, sandy areas, and tolerating a wide pH range. Once established, Smilax is drought-tolerant because its massive, deep root system stores significant carbohydrate and water reserves. Due to its vigorous nature, which can see it climb up to 30 feet, a strong, permanent support structure is necessary.
Support structures must be robust, such as heavy-duty metal trellises, sturdy wooden fences, or arbors. The plant’s woody stems and dense foliage become heavy over time. The vine uses both tendrils and characteristic hooked thorns to latch onto surfaces and climb. Placing the vine away from other desirable shrubs and perennials is a precaution, as its aggressive runners can easily invade nearby plants.
Planting and Initial Establishment
The optimal time for planting Smilax is either in the early spring, just as new growth begins, or in the late fall, giving the root system time to establish. Preparation of the planting area should accommodate the plant’s substantial root structure. The native root system consists of bulbous tubers and rhizomes that can extend deeply, sometimes down to two feet, and spread widely underground.
When planting bare-root stock or a section of rhizome, dig a hole three times as wide as the root mass. The hole should be deep enough to allow the crown to sit at the soil surface, providing space for initial rhizome growth. Backfill the hole with native soil, tamping gently to remove air pockets, and water the area thoroughly immediately after planting.
Propagation from seed is possible but requires scarification and stratification to break dormancy, often achieved by a winter freeze. For a more reliable start, planting from a tuber section is preferred, ensuring a node or emerging shoot is present on the segment. Initial watering should keep the soil consistently moist until the first new shoots appear, signaling successful establishment.
Long-Term Care and Aggressiveness Management
Routine care for Smilax is minimal once the vine is established, reflecting its inherent hardiness. Supplemental watering is rarely necessary except during prolonged dry spells, as the plant’s massive tubers store enough moisture to sustain it. Fertilization is generally not required, and feeding the vine may only encourage its aggressive growth rate.
Pruning is the primary method of controlling the vine’s shape and spread, and it must be done consistently and with caution due to the sharp thorns. Prune the above-ground vines in late winter or early spring to remove dead wood and shape the plant on its support structure. The most important pruning involves managing the underground system to prevent aggressive spreading.
The vine spreads via long runners and new shoots that emerge from its deep, extensive rhizome and tuber network. To manage this aggressive spread, a physical barrier, such as a plastic or metal root barrier sunk 18 to 24 inches deep, should be installed at planting. Without a barrier, constant vigilance is necessary to remove any new shoots that emerge away from the main planting site.
If runners are detected, they must be traced back to the parent rhizome, and the entire tuber section must be dug out. Chopping the vine at ground level will not kill it, as the plant regenerates from deep carbohydrate reserves in its tubers. For established infestations, repeated applications of a broadleaf herbicide, such as glyphosate, on freshly cut stems or new foliage can eventually deplete the reserves. This process may require multiple seasons of consistent effort.