I can't complain about my lawn (well, I guess I can hence this message)
but I'd like to know why my lawn looks even better in little circles
around where I've inserted some basic food spikes to feed trees and
shrubs. The lawn is even more vibrant and a darker green.

On the lawn itself I'm doing basic things: using Turf Builder as
prescribed, aerating twice a year, watering 2-3 times a week. I'm in
San Francisco, so climate is not too hot. Again, it looks decent
overall, but markedly better where the spikes have gone.

Obviously, the spikes are providing even more nutrients, and, it seems
to me, that means I could be fertilizing my lawn even better. But, I'm
a little hesitant to just up the dosage of the Scott's as I think
that's a surefire way to burn out the lawn.

Is there a particular extra ingredient in tree / shrub spikes that I
might consider?

Thanks,

- TK