I read, a fair while ago now, that trees are capable of putting a nasty taste into their leaves if they are very attacked by insects or animals, and that they can pass information that it might be a good idea to do the same on to nearby trees. The comment was made by some one commenting plants ability to comunicate certan information to eachother, there is a horror film about this. So your deliciouse salad leaf may sometimes be bitter and the bitterness is not its normal state but a reaction to a predator. I have noticed this with elm leaves, i have a habit of chewing them and infact elm leaf is used traditionally in the north of spain as salad. They are like lime leaves in taste, as are mulberry leaves. I used to and still do a bit but should not, eat leaves without knowing if I could or not.
I have checked out on moringo leaves and they are eaten and of very high nutritional value. It is a pretty hot country tree though.
I have looked up curry leaved trees and they are eaten too, both choopped small and eaten fresh and fried as the first step in making a curry and fried and sprinkled on food. I t is meant to be a lovely smelling tree, lemony, but does not survive too much frost .
I found out from the behavior of plants on my balcony that some some plants, i have a lot of succulents, i filled muy balconies befor ei read about
permaculture and thought of growign food on them, survive a day or two and more of frost but they dont survive being frozen day after day. So dont despair if sensitive things have had one or two or more days of frost, it is still worth bringing them in and seeing if they will survive it instead of saying it must be too late and leaving them to indure more days of frost.
If the leaves of your curry leafed tree die in spring, wait they will likely as not regrow.
Peopl ealso eat the leaves of the keffir lime as flavouring to dishes. THte fruit is not juicy but its zest is good so if you can grow citrus fruits in you district a keffir lime. agri rose macaskie.