This year, after its first flowering, I cut it back as usual. The new days look nice and green and glossy. Then after a few days, they are wilted, curled up and yellowish.

Why..?!

BTW The jasmine is on a south facing terrace which gets really hot. It is in the shadiest bit of it though it still gets quite a lot of sun. In this heat I water it most days.

Thanks! John_Z.

The unwell one is a pink jasmine. It flowers early, anytime from February to April then again at the end of August or September. As the terrace is third floor, it stays pretty warm (for example my geraniums flower all year except January and February). This year the jasmine flowered in March but then the frost got the flowers. This has happened before, we have fairly warm winters so things flower then we have a cold snap at the end of March.

I cut it right back and it seems to be growing back fine and lots more leaves sprouting, but as I said after a few days they yellow and wilt.
Thanks,
Daisy

If you are seeing death of the stems or branches in addition to wilting leaves, root damage or disease is often a cause, and it can be made worse by over-watering (as Jenny suggested). If there is a fungal infection affecting the root system, it is made worse by the potting medium becoming too acidic over a period of time, as well as a too wet condition. Almost all potting media have a pH drop to the acidic side starting about one year after we start watering it.

There are also a number of bacterial infections that can occur, and some work systemically from the potting mix to the roots and move internally throughout the plant. This also causes wilting of the foliage rather quickly sometimes, but most bacterial infections leave an oily and irregularly shaped soak area on the leaves. Do check for that.

Again, I would check to see if there is death of stem and branches, and if you are unsure, just cut back a seemingly dead branch or twig to see if it still has a tiny green ring within it. If it has it, then the stem is still alive. If it is dead, keep cutting in short increments until you see the green ring. If possible, lift the plant gently out of its container to examine the roots, checking for any dead or rotting ones.

We can't leave out plant pests either as a possibility. If you are not familiar with them, I'll be glad to give you a rundown. For rapid wilting, I would check for spider mites first because leaf curling is common. (Leaf tips also become dry and brown quickly on most plants). Spider mites are a pinhead size and some are even invisible without a x15 magnification. At the advanced stage of building their colony you will see webbing (but not with all species) and usually on the undersides of the leaves first. If the leaves of your plant have a distinct bronze colour, let me know and I'll share info about a new and very non-typical spider mite that is making its rounds.

I'll be in touch!

P.S. The second sentence of my last posting didn't make sense when I re-read it (isn't the first time either) but I think you know what I meant. LOL.