I bought a dipladenia from home depot. When I came home I noticed the tips of some of the stems were brown/yellow/falling off, and it had some brown/yellow leaves. I cut all the dead/yellow/brown off my plant. I was wondering if I killed it, or if it will be ok? The store I got it from had a return policy, so I wondering if I should just go that route. I still have 2 stems in good shape about 8inches long, and the 2inches left from the dead ones I cut back. TIA!
Certified GKH Gardening Expert
This is the start of a fungal infection, likely, from soil remaining too wet for too long. Make sure that the container has plenty of drainage, and if not, then make sure that it never gets rained into.
Make sure to only water when the top two inches of soil are completely dry. This will prevent infection in the future.
You can add a little wettable sulfur and dolomitic lime to the top of the soil, and it will help correct the issue.
This article will help with the care of these: https://www.gardeningknowhow.com/ornamental/vines/mandevilla/growing-a-dipladenia.htm