I have three Queens and three Robinellis(?)in my Arizona yard. They are planted in sand, only way to describe it. During summer I water them a lot and back off to every 2nd or 3rd day Fall to Spring. I have five foot basins around them with large chunks of mulch. My questions relate to feeding/fertilizing.

Do Lutz Spikes work and is that all I need. Is a pellet type feeding better? If so do I need to scrape the bark away and stir the pellets into the ground?

Finally, if there is something better than Lutz Spikes, what specifically is it, i.e., brand name. thanks so much for any tips.