As I have a nectarine tree I was hoping that somebody with more expierience than me would answer it. All I do is trim it back in autumn as I don´t want it growing to high as it is in front of the bungalow window, I then dig in a bit of rottet compost around the trunk and also give it some general fertiliser during the year, this year I had about a dozen nectarine fruit on the tree so what I do doesn´t harm it....and it is still looking healthy and growing well.