I started using fertilizer spikes on my dwarfed citrus trees in small pots. (Details may be found in this question.) As suggested, I used half a spike for each pot and I put the spike as far from any roots as possible.
My understanding is that the risk I'm taking is that the fertilizer will burn the roots of these trees. But I don't know what to look for. Should I check the color of the leaves? What color would I expect from fertilizer burn? How long might it take to see symptoms?