Thick, rope-like stems spiraling up the trunk of a mature tree are common in forests and suburban landscapes. These woody climbers, known scientifically as “lianas,” rely entirely on other structures for vertical support. This specialized growth form allows them to efficiently reach sunlight without investing energy in a self-supporting trunk. Lianas are perennial, woody-stemmed vines rooted in the soil, but their biology is fundamentally different from the trees they ascend.
Defining Lianas and Common Examples
Lianas are distinguished from herbaceous, or non-woody, vines by the development of secondary xylem, the hard, woody tissue that provides significant girth and strength. This woody structure allows them to persist for decades, growing thicker and higher into the host tree’s canopy. They adopt structural parasitism, using the tree’s support system to gain a competitive advantage in the race for sunlight.
Several lianas are commonly encountered across North America, and identification is important for management. Wild grapevines (Vitis spp.) are frequently seen, recognizable by their shaggy, peeling bark and thick, twisting stems. English Ivy (Hedera helix), an aggressive, non-native species, forms dense, dark-green blankets that completely cover tree trunks.
Wisteria (Wisteria spp.) is another common example, often cultivated for its attractive flowers but capable of becoming a powerful, strangling liana. Perhaps the most hazardous is Poison Ivy (Toxicodendron radicans), which develops a thick, woody stem covered in fine, reddish aerial roots as it climbs high into the canopy. Distinguishing these species is important because their growth habits and potential harm vary significantly.
How Vines Attach and Climb
Lianas have evolved distinct biological mechanisms to secure themselves to the vertical surface of a tree.
Twining
One method is twining, where the main stem or a new shoot wraps itself around the host trunk or branch. Plants like Wisteria use this method, coiling their stems tightly in a specific direction as they grow upward.
Tendrils
A second strategy involves specialized, slender appendages called tendrils, often found on grapevines. These tendrils are highly sensitive to touch and coil rapidly around any small support they encounter, acting like miniature grappling hooks to pull the vine upward. Once wrapped, the tendril often hardens, providing a strong anchor point.
Adhesive Structures
The third method utilizes adhesive structures, such as the aerial roots seen on English Ivy and Poison Ivy. These small, adventitious roots emerge directly from the vine stem and contain a sticky, glue-like substance. This allows them to cling tenaciously to the rough texture of bark, ensuring the vine remains flush against the trunk as it ascends.
Impact on Tree Health and Structure
The presence of thick vines on a tree is rarely a benign relationship and can lead to severe decline or death of the host. One immediate impact is light competition, which occurs when the liana’s dense canopy spreads out in the tree’s crown. This foliage shades the host tree’s leaves, blocking the sunlight needed for photosynthesis and starving the tree of energy. Lianas prioritize leaf production over structural wood, making them incredibly efficient competitors.
A second significant problem is the massive weight load that a mature liana adds to the tree, especially high in the canopy. A thick tangle of woody vines holds substantial water, ice, or snow, drastically increasing the total mass the tree must support. This excessive weight makes the host tree more susceptible to breaking or uprooting during high winds or severe storms.
Finally, twining vines can cause girdling, which is a form of strangulation. As the liana stem thickens, its tight coil compresses the soft tissues just beneath the bark of the host tree’s trunk or branch. This compression severs the phloem, the layer responsible for transporting sugars from the leaves down to the roots. When the phloem is compromised, the tree’s root system starves, leading to its eventual death.
Safe Removal and Management
Removing thick lianas without damaging the host tree requires a cautious, two-step approach often called the “cut and wait” method. The goal is to separate the climbing portion of the vine from its root system, allowing the upper section to die naturally. Use a pruning saw or loppers to cut a six to twelve-inch gap out of the vine at the base of the trunk. Leave the vine segment above the cut hanging on the tree, as forcefully pulling it down can rip and damage the tree’s bark.
The cut vine will dry out and decay over time, and the dead material will eventually fall away. After the upper vine is cut, focus on removing the root crown and any vine material on the ground to prevent regrowth. Always exercise caution, especially when dealing with vines that have a hairy appearance, as this often indicates Poison Ivy.
Wear protective clothing, including gloves and long sleeves, to avoid contact with the toxic oil, urushiol. For very large, extensive, or high-climbing vines, consulting a professional arborist is the safest course of action to ensure the tree is not compromised during removal.