We have received a number of inquiries asking whether chipped up Christmas trees can be used for mulch, and whether the chips can be spread now or whether they have to be aged.
The answer to the first question is that they can be used now, as long as the tree was healthy. If you take your tree to a public chipping station, the bag of chips you receive may not be from your tree. However, nearly all Christmas trees come from Christmas tree farms where they are well cared for and are not likely to carry insects and diseases. Most municipalities will use chips that residents don’t take to mulch around public trees. A few may use them only for trails.
In answer to the second question, you can use the green chips if you just spread them on top of the soil. If you mix them into the soil, they could pull nutrients from the soil.
This conclusion is the result of research by a prominent arboriculture professor who planted a dozen trees. He left four unmulched as a control. He spread fresh chips on the soil surface around another four trees and mixed chips into the soil around the last four. After a year, he found no difference in the soil nitrogen between the surface mulched area and the control trees and only a slight decline in the amount of nitrogen where he had mixed the fresh chips into the soil.
If you are concerned about using fresh chips in your own landscape, just mix in some fertilizer before spreading them. This holds true for chips from trees you have had pruned as well as your chipped Christmas tree.
The professor’s conclusion was in an article that appeared in two trade magazines several years ago. This professor was one of three prominent research arborists the author spoke to when researching the article. All three of them said that fresh chips would not deplete soil nutrients, and that fertilizer could be mixed in if you doubted these conclusions.