The mandevilla plant in my yard is losing leaves.

Question

I have it in the sun, in it’s original pot with a trellis for it to grow on. The leaves are turning yellow. A few of the vines are dried at the end.

Answer 1

It could be due to watering, too much or too little, lack of fertilization, disease or insects. Here is information that covers all these points; you can see which one fits your situation. Also, since it is in its original pot, which may be small, you will need to water more as the moisture will evaporate quickly. It may need to move up to a larger container.

https://www.gardeningknowhow.com/ornamental/vines/mandevilla/yellow-leaves-on-mandevilla.htm