Trip? No idea what you mean.
I have never fertilized my lilacs, neither the huge old one or the two younger ones, one of which was a little volunteer I moved to a new spot. They fend for themselves quite well.
See my post here:
all I do is deadhead and prune a little (mostly cutting the dead wood out and opening up the center a bit so sun, air etc can get through, keeping branches from rubbing against each other)