mandevilla leaves turning yellow
In the past week or so my mandevilla leaves have started to turn yellow, some with some small brown blotches, and the leaves are falling off. This is widespread, not just at the bottom. The plant is otherwise doing extremely well, growing well, with lots of flowers. It is in part shade and I checked the roots for sogginess and they are fine (not soggy, not dry). I use a dilute fertilizer every few weeks that is - - .
Certified GKH Gardening Expert
Since there are brown spots in addition to yellowing leaves you may have some fungal leaf spot going on. Here is info on how to treat it, plus other environmental and disease causing problems.