Q. We recently purchased a chipper/shredder and have disposed of many branches from fir trees this way. I noticed that leaving it in a pile, it gets very hot and turns to like ash within a week, in the center of the pile. If I spread it over my garden, it turns to like a beauty bark color, and doesn’t get hot after a week or two. Can I use this as a mulch, and do I need to use it after it turns to ash like, or just let it sit on the garden? Do I need to put anything else in the soil when I use it? Thanks, Midge Patten – Allyn, WA
A. The reason the pile gets hot and changes consistency so fast is because the green needles and the brown wood shredded together supply the ideal ratio of carbon (brown) and nitrogen (green) for the aerobic (oxygen using) decomposing microorganisms. The act of shredding also provides more surface area for the decomposers to work on. Although it is not critical to allow the mulch to decompose for a week if you like the more uniform consistency of the product then by all means use it. You do not need to add anything to the soil since the mulch sits on top of the soil and will only use nitrogen from the very surface of the soil leaving the nitrogen below available for the plants’ roots. As I mentioned to Mardell be sure to apply it at the proper thickness. So if you have shredded it very fine two inches will be enough. If it is fairly coarse then you can go up to four inches.