Trumpet vine (Campsis radicans) is a true North American plant. Native to the Southeast, it grows in most areas of the continent and is able to take the cold and the heat in stride. But it's northern gardeners like me that appreciate it most: Few hardy vines can offer an equal amount of color and vigor. Many garden plants are described as blooming all summer long, but trumpet vine is one of the few to actually live up to this description. Its only requirements are a sunny exposure and a good pruning in winter.
I became acquainted with trumpet vine when I first bought a house and got serious about gardening. It was August when I moved in, and the garage wall was covered with hundreds of large trumpet-shaped orange blooms that attracted hummingbirds. It took me some time to find out what the spectacular plant was. Trumpet vine is very woody and at first I was under the impression it was a tree that had grown right against the wall. A closer inspection revealed adhesive suckers and eventually I found it identified among climbing plants.
The next spring, I was worried when the plant didn't show any sign of life. I had been looking forward to a repeat of the "wall of blooms" from the previous summer, but the plant looked just about dead. Then, late in spring, it started showing a few green sprouts. I then realized that trumpet vine, even if it could easily put up with my USDA Zone 5 Canadian winter, likes heat and would wait for it before coming out of its long winter sleep. Nonetheless, it will survive areas as cold as zone 4, although in this zone it may suffer winter damage. While it is very adaptable, it has not become a problem plant and it does not tend to invade areas where it is not native.
Our North American native species, Campsis radicans, produces large, 3-inch-long, trumpet-shaped orange flowers at the tip of each year's new growth. 'Flava' and 'Aurea' are yellow varieties of the same plant. In my experience, neither is as hardy as the species. Each leaf is divided into as many as 11 leaflets, each 2 to 3 inches long.
Campsis grandiflora (aka Bignonia chinensis) is a Sino-Japanese species, which can be grown in mild climates. It won't survive long periods of frost. This trumpet vine is very similar to C. radicans but blooms in late summer and fall. The variety 'Thumbergii' has shorter but wider flowers. This plant is hardy to zones 7 through 9.
The two species, C. radicans and C. grandiflora, have been crossed to produce Campsis tagliabuana, which produces large attractive salmon-red blooms. Like its Chinese ancestor, it is more cold sensitive than the native, but by most standards is still reasonably hardy, to zone 7. It is also very tolerant of alkaline soil. Common varieties include 'Crimson Trumpet' and 'Madame Galen' (salmon-red flower).
Trumpet vines are fast growing and are mostly used on walls where, if you let them, they will reach 40 feet. They are self clinging with aerial roots. However, much of the weight is supported by the woody trunk, which gets to be as large as the trunk of an old lilac bush. The exposed large trunk looks very good on the side of pergolas (although on a pergola the blooms are more easily admired from the outside than from the inside). They work particularly well as covering for a dead tree trunk, provided it is in the open and gets plenty of sun.
Trumpet vine has one big drawback, which is that it suckers a great deal. New shoots appear all around the plant. I believe this is the key reason the plant is more appreciated in the North, where winter helps keep the plant in check. In my zone 5 garden, it's not a problem, perhaps partly due to my region, but also because lawns mostly surround it. The new shoots that push through the grass are mowed with the grass. However, if, like me, you have a gravel path next to the vine, some shoots will appear in the gravel in July and August and will have to be pulled out. You will also have to rake up the numerous blooms once in a while as they start fading and falling onto the ground.
To give you a lot of bloom, trumpet vine needs to have a very sunny exposure. In the northern part of its range, a southeast facing wall where it gets maximum heat and sunshine is ideal. In more southern climates, it can put up with some shade. In places with less sunny summers, such as Northern Europe, trumpet vine does not bloom as reliably as it does in most of North America. It is very accommodating of soil and pH and has no serious pests. I will sometimes notice a few scales on mine, but they don't seem to do any visible damage and the plant has been growing for over 20 years. Another requirement for good bloom is an annual pruning.
Pruning trumpet vines is very straightforward and simple to do. Usually the plant is grown on a wall. You have a stem and some main branches that cling to the wall. Each spring, bunches of whips (3 to 4 feet long) grow out of these branches and away from the wall toward the sun. These are covered with leaves and, at their tips, a great many orange trumpets appear in early summer. In the first month, the quantity of bloom is quite spectacular, and contrary to, for instance, most reblooming roses, it remains impressive for most of the summer.
Once all the leaves have fallen after the first frost, you are left with "sticks" growing out of the main branches, away from the wall. You simply have to cut off all of these sticks at the base and the following year new ones will appear to once again produce a magnificent display. This pruning can be done any time from after the leaves have fallen until spring. It is an ideal job for the middle of winter when there are fewer things to do in the garden.
If the plant has been neglected for a few years, prune off everything that is not growing on the wall. This will ensure good blooms the next year. To give it the shape you want, you can also remove branches growing on the wall in inappropriate places (like at the top of the wall or under the eaves troughs).
After pruning, you are left with a bundle of woody but flexible whips that are 3 to 4 feet long. These are excellent to recycle as stakes for peas or for plants with heavy blooms such as double peonies. They can also be bent and used to support short plants such as dianthus. In this case, bend the stems and insert each end into the ground, making half loops through which your plants will grow and support themselves. You can also use these loops in pots.
Alain Charest, an avid home gardener and garden photographer, lives in Kitchener, Ontario, Canada.
Photography by Alain Charest
Article published on June 23, 2008.