Word of the Week: Twine

twine [ twahyn ] verb: to ascend by clockwise or counterclockwise spiraling or coiling around a support

 

Akebia quinata stems twine counterclockwise.
Photo © Mary Free

Climbing plants use different methods to support themselves as they grow: aerial (adventitious) roots, holdfasts (adhesive discs), petioles (leafstalks), spines/thorns, tendrils (thread-like appendages), or stems that twine. Knowing how a plant attaches itself allows you to choose the right vine for an existing support structure or to purchase the correct support for a new plant.

Plants like Akebia, Gelsemium, Lonicera, and Wisteria use twining stems that wrap themselves around a support like an arbor, chain-link fence, column, pole, trellis, or wire. All vines of the same species twine in the same direction, although all species in the same genus may not. A few species can vary their coiling direction from one internode to the next. If you manually coil a young stem around a support contrary to its natural inclination, it tries to unwind itself and revert to its characteristic direction.

Invasive Akebia quinata (five-leaf akebia, chocolate vine), annual Dolichos lablab (hyacinth bean), and natives Gelsemium sempervirens (Carolina or yellow jessamine) and Wisteria frutescens (American wisteria) twine counterclockwise (the stem goes up from left to right if you observe it from the side). (Ferréol and Mandonnet 2018) Humulus lupulus (common hop), native Lonicera sempervirens (trumpet or coral honeysuckle), and invasive Wisteria floribunda (Japanese wisteria) are examples of clockwise twiners.

Most vines twine counterclockwise. It is not known why plants twine in a specific direction, but research has shown that direction is not random, nor is it determined by the movement of the sun or the location (hemisphere) in which the plant grows. (Edward et al. 2007) How quickly a vine coils depends on the species, its growth rate, and external factors like light and temperature. “Akebia quinata may be said to hold the speed record completing a full revolution in one hour and thirty minutes.” (Lofgren 1973) In addition, this non-native vine can grow 20–40 feet in a season, a combination that makes it an efficient and ecologically dangerous invasive species.

Some plants like natives Bignonia capreolata (cross-vine) and Campsis radicans (trumpet-creeper) use a combination of methods to climb. Although tendrils are crossvine’s primary support it also twines and uses holdfasts when needed. The aggressive trumpet-creeper mostly uses aerial roots but can twine as well and needs an exceptionally sturdy support. Native Clematis virginiana (virgin’s-bower) uses twining petioles instead of twining stems to climb.

Note: The direction in which a plant twines can help one to identify the plant species, however some botanical and horticultural sources confuse clockwise and counterclockwise twining. To determine twining direction, it is easiest to visualize the stem as a cylindrical helix looking at it from the side. A stem twines in a counterclockwise direction and is considered “right-handed” if it coils up from left to right. A “left-handed” stem twines clockwise ascending from right to left. (Ferréol and Mandonnet 2018) From the Akebia pictures above, for example, there can be no doubt that the stems coil in a counterclockwise direction.

References

Edwards W, Moles AT, Franks P. 2007. The global trend in plant twining direction. Global Ecology and Biogeography, 16:795–800. http://dx.doi.org/10.1111/j.1466-8238.2007.00326.x.

Encyclopédie des Formes Mathématiques Remarquables. Cylindrical Helix, © Robert FERRÉOL, Jacques MANDONNET 2018.

Lofgren DO. 1973. Climbing Plants. American Horticulturalist Spring, 52(1):26.

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