Anyone ever use Miracle-grow spikes?
 

I have been using these spikes for our evergreens/fruit trees/regular
trees/bushes for the past two years. They seem to work, but I'm not a 100%
convinced. Our birch tree has grown quite a bit from using them and the
evergreens seem to be a lot more green with minimal growth. However I was
just wondering what the general consensus is on the NG about the spikes?
Pros/Cons? I know when I place them around the trees in our yard it results
in what I like to call crop circles in the grass. The grass above the
spikes tends to grown much faster than the rest of the yard along with being
thicker/greener. It eventually dissipates as the summer wears on, but
initially looks strange. Our yard also receives 6 treatments a year from a
lawn care company called Natural Lawn Care at http://www.nl-amer.com/ .
I don't want to be over fertilizing our yard with the spikes, which is why I
mentioned the lawn care. Any opinions/comments are welcome.

Thanks,

-Jerry