I brought my Mandevilla in last fall and cut it down to 2ft. In sunny window almost all day.
Now it's February and I'm getting a lot of yellow leaves droping now. What's up!!
Our answer comes from Viette Garden Center Manager, Gerry Coggin:
Your Mandevilla is just going through its normal cycle. I winter my mandevilla in a greenhouse set at a 40 degree F minimum temperature and they not only turn yellow, but they turn brown and lose all of their leaves.
In mid-March, I will prune them and start fertilizing and they will come back as they have for the past 10 years!
Mandevilla can be cut back by hand to 2" from the soil level. If you have a trellis with vines attached, thin out 20% of the weakest spindly vines. Then cut the remaining growth back to healthy buds or branches.
They are now ready for the new season. Set the plant back outside after the threat of cold weather has past.