Evergreen tropical vines, mandevillas aren’t shy about blowing their own trumpets — trumpet-shaped flowers, that’s. With blooms in shades of red, pink or white, the plants are often sold as potted annuals, because most species are only perennial in U.S. Department of Agriculture plant hardiness zones 10 to 11. The exception is the Chilean jasmine (Mandevilla laxa), which may survive outdoors in USDA zones 7 to 11, but will die back to the ground during winter at the colder end of the range. Although they churn out a lot of buds, mandevillas sometimes shed them too, for an assortment of reasons.
The Light of Day
Mandevillas need sunlight to bloom well, but full sun all day, every day may be too much of a great thing for some plants. Based on GrowerTalks magazine, “high light throughout the summer can lead to bud abortion .” If your plant looks somewhat bullied, shift it into a place where it receives full sun only in the morning rather than during the brightest hours of midday.
A Long Drink of Water
Too much water or too small may also lead to your mandevilla to discard buds. It’s tuberous roots which decay readily when compelled to endure constantly soggy conditions. In case your mandevilla is growing in a pot, be sure that container has drainage holes and is filled with a light and porous potting soil rather than heavy clay, so that excess water does not linger. On the other hand, you shouldn’t allow the soil to become parched either, or even the plant will cast off buds that it can no longer sustain.
A Chunk of Change
If you opt to bring your mandevilla inside in the autumn to preserve it to the subsequent summer, then it will almost inevitably lose buds due to the shock of this transition. The environment in most homes is much lower in both humidity and light than that which the plant will have experienced outside. As opposed to attempting to keep it growing under these conditions, you can force the plant to semi-dormancy over the winter. To accomplish this, cut it back to about 10 inches, then put it in a cool, dark area with temperatures in the 50s or even 60s Fahrenheit, and water it only enough to keep the soil barely damp until spring. Be sure to disinfect your pruning tool blades by wiping them off with alcohol prior to pruning. This will decrease the chances of infecting the mandevilla with any diseases still clinging to the blades from a previous pruning job.
Left Out in the Cold
Regardless of the shock your plant might need to endure when brought inside, it is not a fantastic idea to leave it out too late in the autumn, either. A sudden freeze will destroy most mandevillas, with the exception of Mandevilla laxa, and they aren’t fond of temperatures in the 40’s F, either. Most types will begun to sulk — and also possibly cast buds — once night-time temperatures fall below 50 degrees F., and they should be brought inside at the moment.