I potted my pink dipladenia hanging on the rails outside my balcony and it was flourishing beautifully for about 2 months. Foliage grew and flowers blossomed every day. Then suddenly the leaves started getting brown around the edges (no yellow nor gray nor little holes. Just dark browning) making the leaf look and feel "weakened" and eventually falling off (before turning fully brown or dry. Still greenish but softer and weaker). Suddenly the plant lost most of its volume. It still blooms but the flowers last less time and some fall off before blooming.
The browning is not in one particular area, but it appears on random leaves around the plant. No bugs to be seen anywhere. I tried taking off the affected leaves but new ones appeared by themselves.
I tried fertilizing for the first time. Nothing changed except some new flowers appeared.
Does not look like blight. And it kinda looks like burning from the sun, since it does get a lot of hours of direct sunlight and im in a pretty hot area. But that wouldnt explain why only the edges look burnt or why some leaves that are more hidden are also browning.
The pot has 4 holes under it and i water it when the soil is getting dry but not bone dry, and I let the water flow through until it flushes out of the holes.
Am i doing anything wrong?
Thanks!

Hello danybrugn, what is your prevailing daytime temperature and humidity levels there right now. Your location is a broad Middle East, are you situated coastal or more inland there?

I have a similar plant but it is a mandevilla, blooms during the early part of summer as long as temps are still okay like around 75F to 85F. Any higher and it will blast the buds, and with our lousy humidity here, the leaves are like burning too. So I really have to step up watering, spraying the leaves a lot while it is still in some part shade, before our very hot sun hits it. It likes bright light and warmth, but not scorching dry heat.

Dipladenia has been absorbed by Mandevilla. They are synonyms.

tarev said:Hello danybrugn, what is your prevailing daytime temperature and humidity levels there right now. Your location is a broad Middle East, are you situated coastal or more inland there?

I have a similar plant but it is a mandevilla, blooms during the early part of summer as long as temps are still okay like around 75F to 85F. Any higher and it will blast the buds, and with our lousy humidity here, the leaves are like burning too. So I really have to step up watering, spraying the leaves a lot while it is still in some part shade, before our very hot sun hits it. It likes bright light and warmth, but not scorching dry heat.

I tarev, thank you for your answer.
I am on the coast and its very hot and humid. About 30 degrees C today but it gets hotter, and the sun is pretty harsh. The plant is in the sun on my windowsill as I have nowhere else to put it where it would get enough light. The leaves have started growing back by themselves and the plant looks somewhat healthy except for those random few leaves that just brown and fall. After a while this started happening also to my geraniums, which are sitting right next to the dipladenia. In the case of the geranium, though, the leaves are born yellow and they brown and fall before they even get to their full size. I fertilized them yesterday tho so ill see if they were just missing some nutrients as i hadnt done it in a while. But the dipladenia just looks beautiful except those weirdly burnt leaves. Maybe it really is just the sun
Thanks again!

Hello danybrugn, good to know you are on the coastal side. One thing you have to remember with plants, if it is visibly showing distress already, do not apply fertilizers. At times it will just further hasten leaf burn or root burn.

Yes, the sun is really something else during summer time. As much as the plants need the sun, they do not however need to be badly fried with it. Over here we get very dry and hot temps here, and the thing that protects my plants is some shade from our city trees. In your case, is it possible to have a white sheer screen so you can protect your plants during the hottest time of the day? I also find that it helps to water spray the entire plant early in the morning, before the hot sun hits it.

Observe the leaves too, if the drying out leaves are the lower ones, that is okay, older lower leaves eventually dries out first. As long as you have new leaves forming, then the plant is coping as much as it can with the excessive heat conditions. It will only sustain what it can provide moisture, so it will drop the older ones first.