my neighbor had 2 pine trees, and i used to pick the cones up (and needles, but mostly cones)
and add them to the garden as mulch,, for years i did this.
he got rid of the trees, but the planter had years worth of decaying cones and needles
i planted 2 papaya in there, and they really took off.
i went 2 years without adding anything to it, and it was still rich "compost" like stuff
when you dig down...
now i am adding leaves and grass clippings, but, its not the same
they break down much faster.
i am eyeing up a couple of pine trees on the roadway near here
the cones are great stuff IMO, the needless are a bit of a pain to get up
unless you have a wide rake and several big trees.