Those old socks make excellent mulch :D Seriously, if you have enough compost to do that God Bless You. Most of us have trouble getting enough for soil amendment. It would depend, to a degree, on the type of compost but rough, partially finished compost, such as you described, ought to be great for mulch. Every time you water it will leach out some nutrients into the soil so you would get the double benefit of mulch and nutrients.

Assuming that your first mulch is an organic material such as bark or wood chips, I don't think so. I did something similar. I added new compost a year or two later and the original mulch was only partly decomposed. So I "stirred" the two together so that the compost was available to the plants easily, then put new mulch on top of that to protect the compost from the sun. It is my opinion that you would want to avoid stirring these two into the soil where the decomposition would bind nitrogen during the process. However, current thinking is that if the decomposition takes place on top of the soil, only the contact layer of soil is affected. If you are using a non-organic mulch then yes, I do think you will want to try to remove it. Rosefolly

I practice a two-layer approach. In the spring after pruning I scatter an organic fertilizer, often using alfalfa meal. I usually do not fertilize again (except in my vegetable garden). Then the first layer goes down. Each year I alternate, one year using composted city yard waste, the next year a high quality composted stable manure available nearby. If I lived in a higher rainfall area, I would use the stable manure every year, but I don't want the salts to build up in my soil. On top of the compost goes a mulch of mixed tree trimmings. As Berndoodle mentioned, it is large and coarse. However, much of it breaks down over a year or two. The remnants of the previous year can easily be raked aside to put down the compost, then replaced on top. The purpose of the mulch is to preserve water, moderate temperature, shade out weeds, and very importantly to protect the compost. It breaks down slowly and eventually improves the texture of the soil. Once upon a time there was a lot of concern that wood-based mulches would rob the soil by tying up nitrogen as it decomposed. It is now believed that this only happens at the contact layer so long as you don't mix it into the soil. Furthermore, by using wood material that includes greens (leaves), this is greatly reduced. I get my wood-based mulch free from a local tree-trimming service. You do have to take a truck load of you go this route, so it may be necessary to purchase it if your garden is small. Rosefolly

Personally, I wouldnÂt use thorny materials in the compost pile to lessen the chance of getting pricked, and have not done so. But if the compost is well aged, all organic matters would crumble into fine, small granular so that you may not even see shape of thorns afterward. It may be easier to chop the canes to less than a foot long or so for easy mixing with other green materials, and wear thick gloves.