Answer: Mandevillas are typically used as a vine, but just as bougainvillea and trailing fuchsia, the oldest stems can become woody so the plants can be trained into a single trunked tree form or a multi-trunked shrub. It takes years, but the effect is worth the time and trouble.
Start by supporting the main stems of your plants so they remain upward. You can use metal rods, bamboo stakes, or cedar stakes. You'll want to tie the stems firmly with pliable material that will expand as the stem grows. Every few months you'll want to check the stakes to make sure the stems are growing upright and are not girdled by the string or plastic ties. In the late winter or early spring you can prune the long vines back to encourage new growth, but you'll want to allow the main stems to remain at the height you've chosen. These stems will eventually grow bark which will help them remain rigid and in an upright position. You'll be able to remove the supporting stakes in 2-3 growing seasons. What you'll end up with is a shrubby form and as the vines grow they will hang down over the stems, giving your mandevillas an interesting umbrella like form.
Q&A Library Searching Tips