Can I compost pine needles or pine cones?
Pine needles can be composted, but their decomposition will be slow. Needles and cones will decompose faster if they are broken into pieces to increase the surface area. You can do that by running over them with a lawn mower, chipping/shredding, or breaking them up with the back of a rake. Modest quantities can be mixed into the pile as a texturizer to help keep the pile aerobic. But even under the best conditions, cones and needles won't fully decompose quickly (five to six weeks).
Shredded pine cones and pine needles make good mulch even without composting. Because of the high carbon content, be cautious about burying either in the soil before most of the decomposition has taken place (the microorganisms associated with them will consume nitrogen from the surrounding soil as the high-carbon material continues to decompose).
Two cautions: 1.) When used on a slope it will become very slippery. You may break or bruise something precious. 2.) Pine needles are very combustible and are not recommended for use next to buildings (homes).