The lone voice of horticultural reason

“You need to add extra nitrogen to the soil anywhere you use shredded bark or wood chips as mulch.”

 Not true, but I do like the fact that this newer myth originated from people starting to hear and learn more about soil science.

Yes, wood that has not been composted will eat up a lot of nitrogen when dug or rototilled into the soil. Fresh sawdust in the soil or compost bin is a common culprit. Add sawdust to your soil (or uncomposted grass clippings, or shredded leaves) and foliage will turn yellow pretty quick. But shredded bark or wood chips in a four- to six-inch layer around your trees and shrubs is on top of the soil, not in it.

Your standard fertilizer program for trees and shrubs from spring through August 15th will add more than enough nitrogen to compensate for the negligible amount lost in the surface soil as wood mulch decomposes. If you never fertilize your trees and shrubs and use a wood mulch, then you really should break down and start using some fertilizer in the spring, and then at least one more time, say around the end of June.

But that’s more for the overall benefit of the plants than to compensate for any problems caused by wood mulch eating up nitrogen. And remember, granular fertilizers beat the pants off water-soluble fertilizers every time.

Don Engebretson
The Renegade Gardener