Trumpet vines (Campsis radicans) and their magnificent, fiery flowers are appealing, but putting these strong vines near a building can have repercussions for the construction and the vines. Growing in U.S. Department of Agriculture plant hardiness zones 4 through 10, trumpet vines want the ideal sun and dirt for showy flowers, and neighboring buildings affect these. Before you plant, then think about the future health of the vines and the building.
Trumpet vines make their keep with an extended show of trumpet-shaped, tubular blooms. Apparently made for hummingbirds, the nectar-heavy flowers grow around 3 1/2 inches long and nearly 2 inches wide. Clustered together in groups of four to 12, the flowers cover vine hints in vibrant color — if the vines receive ample direct sun. Nearby buildings can interfere with the minimal six to eight hours of full, direct sun trumpet vines need each day. If a building shades the plants considerably, expect poor development and few blooms. You’ll also miss out on the vines’ ornamental, 6-inch seed capsules.
Trumpet vines handle wet to dry dirt, even drought, and soil types from mud. Soil with a pH between 3.7 and 6.8 suits them best. Higher pH levels brief the vines of nutrients. Many alkaline construction materials, including concrete foundations and walkways, raise soil pH as they age. Planting close to these building materials can affect trumpet vine health. Lawn fertilizers also impact trumpet vines in undesirable ways. High-nitrogen bud fertilizers stimulate green, leafy growth at the expense of flowers.
Trumpet vines rapidly grow to 35 feet or more and more frequently need extra support. Sturdy pergolas or arbors may function as stepping stones to buildings nearby. The vines climb by twining stems and also by ample rootlike stems. Tiny aerial rootlets along these stems attach to rough surfaces and wiggle their way into tiny crevices. They damage wood, stone, stucco and brick. Without added support, the burden of trumpet vines frequently pulls these substances down, bringing drain spouts and gutters with them. The small roots stay connected to the wall or tear away, leaving stained and damaged surfaces behind them.
For all its beauty, trumpet vine can be ruthless. Unchecked, the invasive vines conquer nearby plants together with buildings. Spreading rapidly below ground and above, root suckers spring up everywhere they can. Mowing and hand-pulling keep suckers down, but shoots may multiply in response. Eradicating roots for a redesign can be challenging — both airborne and underground remnants. Prune trumpet vines, as needed, at any time of the year to keep them confined. Use sharp bypass pruners and sterilize the blades with a spray family disinfectant before and when you prune. Trumpet vine sap irritates skin, so wear protective clothing, including gloves and eyewear, when you prune.