How to Train Climbing Plants to Climb a Pergola
Quick: What do ivies, grapes, morning glories and squash have in common?
Answer: They’re all climbing plants.
Few sights are as soothing to the human eye as that of magnificent flora rambling over a cedar pergola. Have you been drooling over the neighbor’s wisteria, wishing for your own healthy climber? This article will relieve such envy by summarizing how to get different types of plants to climb up a structure such as a pergola.
In the evolutionary storybook of life on this planet, climbing plants are distinguished by their reliance on outside structures. These plants do not have the structure to support themselves, so they must grow on walls, branches, trees or rocks. Climbing usually allows plants to obtain maximum sunlight with minimal energy expenditure. In the rainforest, for example, a vine may be able to grow toward sunlight that self-supporting plants cannot reach.
Botanists and landscape designers categorize climbing plants according to their climbing equipment. By understanding how these plants adhere, you will be able to get them to drape over nearly any support.
Climbers use five types of attachment mechanisms: tendrils, hooks (think thorns), twining stems, aerial roots and sticky pads. Let’s take a closer look at each family of climbers.
Tendrils
Peas, grapes, pitcher plants and hops use tendrils to catch hold of nearby support, such as twigs and branches. The plant explores its space by waving around its tendrils, which are thin sections of spiraling, stem-like growth. Once the tendril finds something to cling to, it coils around it through changes in internal pressure (“turgor pressure,” in landscaping circles) and variations in cell growth rates.
Plants that use tendrils may not be able to coil around thick supports. If you find that your tendril-based climber is not catching hold of the support you’ve chosen, you may need to provide a support with less girth. One way to do this is to drape wire or mesh over the support
structure. You will find the most success if the mesh has squares that are larger than 2 inches.
Or you can simply prop up a stick with plenty of side shoots to support the climber, or even string wire or twine across supports. Most tendril vines will not catch hold if there is more than 4 inches of space between the tiers of support.
Hooks
Roses are one example of climbers that use hooks to ascend. Because such hooks (thorns, in the case of roses) are not able to truly attach to an external support structure, it is more accurate to say that these plants “scramble,” not climb.
To ensure that a hooking climber has sturdy support, you may need to attach the plant to the structure via twine, wire or any commercial tie. Do not tie the plant too tightly to the support, as it must have room to grow in diameter as well as length.
Twining Stems
Probably the easiest way for a plant to climb a skinny, tall structure, such as a pole or a slender tree trunk, is to twine its stem around the support, usually toward the light. Morning glories and wisteria belong in this category. You won’t have to work too hard with this type of climber; plants that use this climbing method will usually twine around any structure in their path. (Twine or wire ties are always handy for times when you want to direct a plant a certain way.)
Some twining climbers are so strong that they can literally choke the life out of their supporting tree. Some of these plants can be quite heavy, too, so you must be sure they have the right kind of support. Be a wise gardener; do not plant aggressive climbers against key support structures.
Aerial Roots and Clinging Pads
Another evolutionary adaption for climbing is the use of roots or sticky pads. If you take a close look at English ivy, you’ll find it adheres to sheer walls via clinging stem roots (aerial roots). These short, sturdy root hairs emerge from the vine itself and allow the plant to exploit irregularities in a rock face or brick wall.
Clinging pads are a similar evolutionary development. A careful examination of Boston ivy will reveal that the plant sends out sticky pads to attach itself to walls. Vines with clinging pads are the Spidermen of the plant world—they can grow against nearly any surface, thanks to their self-made glue.
Training Tips
Now that you know the array of plant climbing techniques, you have an insider’s perspective on how to coax climbers to grow as you wish. Take a few additional tips into account before planting climbers willy-nilly:
- First, remember that these plants can be surprisingly strong—not to mention heavy enough to pull down buildings. Some gardeners refuse to plant wisteria on house frames for this very reason—wisteria has a tendency to weaken and take over structures. A steel post or sturdy pergola is the perfect home for such a strong climber; wisteria needs a strong frame of support that won’t be susceptible to structural weakness.
- The rate of growth can also make a big difference. If you plan to be in your home for several decades, a slow-growing, gentle climber is generally a good choice.
- Finally, consider the placement of your climbing structure. What kind of sunlight, water and exposure to the elements will a plant in this spot receive?
Thinking about conditions before you place any plant will save you headaches down the road. If you figure out what your favorite climbers need beforehand, you’ll be able to give them the right growing conditions to let them thrive.
~Colleen Welch, 2010
