I have a few summer vines growing in containers with climbing supports on the front walkway and back deck. These include ‘Heavenly Blue’ and ‘Star of Yelta’ morning glories, moonflowers or belle de nuit (Ipomoea alba), and cardinal climber or cypress vine (I. quamoclit). I wanted a passionflower vine (Passiflora alata), but couldn’t find one this season. However, I did acquire a beautiful Rio Deep Red mandevilla (Mandevilla laxa ‘Fisrix Dered’). I had been looking for a white mandevilla, then saw this one with gorgeous deeply saturated red flowers with yellow-orange throats and had to have it. The colour is so intensely red and the petal texture is like velvet—who could resist? Not me!
Mandevilla vine care
Mandevilla vines are tropical perennials used as annuals in our cold climate, although you can bring them inside in early fall while night temperatures are still above 10°C. (Cut the vines back by one third, and keep the plant by a bright window, watering only enough to keep the soil slightly moist.) They will probably lose some leaves indoors, reacting to the lower light, but will stabilize and can be moved outdoors again the following summer when night temperatures are reliably above 10°C again.
I potted my new mandevilla into a larger container, gave it a climbing support, and placed it in a sunny spot on the front walkway. After two days in bright sun, the flower colour began to change. The intense red was developing black flushes, a feature that I’ve seen in other red flowers. (I once had a ‘Chat Noir’ cactus dahlia with dark red petals flushed with black.) But I’m sure the mandevilla petals didn’t have these flushes when I bought it. I checked Internet descriptions of the plant, but nothing mentions black in the petals, and my thought is it really shouldn’t be there. My mandevilla is blushing black!
I guess location is everything in the garden. You can get the right plant, but then you’ve got to put it in the right spot. I think the black flushes on the red petals, though very pretty, are signs of stress. This plant is getting too much ultraviolet light, and needs a part-shade location. I’ve seen roses develop bronze-black flushes (thought to be a temporary accumulation of anthocyanin pigment) on their spring shoots and foliage to protect tender new tissues from sunburn, and the black-blushing mandevilla may be doing the same thing. I’ll have to cart it around to the back deck where there’s only three hours of direct sunlight. Fortunately, I’ll see it there more often, so it’s a case of right location for both plant and gardener.