Mandevilla advice

Question

Good morning, I believe I have a mandevilla that is not doing so well. I have two of them and one seems to be doing ok while the other has some leaves that have turned brown. I’m using these as my wedding flowers in 2 weeks and worried I am doing something wrong. I keep them in my living room which is bright but they are not in direct sunlight ever. I have read conflicting articles saying they like moist soil as they are from Brazil but I have also read that they like to dry out between drinks. They are in pots about 1 ft in diameter with a hole in the bottom. The one not doing well is in rich heavy black earth and the one that is doing well is in more of a vermiculite (lighter and looser). I have been watering about once every 2 weeks when the soil feels dry a few inches deep. Any and all advice appreciated, please help save our wedding flowers. Thanks in advance for your time and knowledge!

Answer 1

The soil in the pot with yellowing leaves is probably not giving the plant what it needs. You should consider repotting that one with a fresh soil mix. This article will tell you what this plant requires:
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/mandevilla-plant.htm
Here's another article that will help:
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/yellow-leaves-on-mandevilla.htm