I Live in Oshawa. I acquired a Mandevilla In early summer and it flourished on my south facing porch fairly well. I brought it inside in October. I don’t have any spot that provides good natural daylight indoors. I provide the plant with 6 hours daily Nanotech Light. I see a dark brown Growth/Deposit on the leaves , and they are curling as well. Any Ideas as to what is happening? I don’t want to lose the plant. Thank you
Thanks for contacting Toronto Master Gardeners. There are several possible reasons why the leaves are turning brown and dropping off your mandevilla vine. First off it is probably having a hardtime adjusting to the new environment. Mandevilla vines prefer to be outside and tend to lose leaves in the winter. They like the humidity and if the nanotech light is hot that might be reducing the humidity in the air. To help the plant you can cut back little on watering, prune it back a little, increase the humidity as much as possible and let it get used to the new environment. Next year, bring the plant in a little earlier – October outside versus inside the house is too much of a difference (temperature, light, humidity) which is why it’s having trouble adapting. Also check for insects. If you see webs, spider mites might be an issue. White flies, another type of insect that attack mandevilla vines look like small moths. If either type of insect is present spray the whole plant with water including the undersides of leaves on a weekly basis until it’s no longer an issue. Once you put the plant outside next spring, it should rebound. For more information, please review the following links:
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/winterizing-mandevillas.htm
https://homeguides.sfgate.com/mandevilla-leaves-turn-yellow-67344.html
https://homeguides.sfgate.com/sick-mandevilla-plant-75343.html