Last time, we discussed the first step in a well done mulching job. I say well done because I have seen some pretty bad commercial landscape mulch jobs in my day, some of which almost qualify as Crimes Against Horticulture. Beyond the classic volcano mulch issue, I see mulch half covering the lower limbs of trees and shrubs, or mulch spread at inconsistent depths, creating the look of a choppy sea (unless that is the effect for which you are aiming). To my mind, mulch should be spread consistently, smoothly and not spread haphazardly about, especially into that nice new edge you created after you read last week’s blog. Doing so would destroy definition and provide a means for grass to invade the flower bed.
One of many mulching mistakes people make is how often they mulch. We love the fresh look new mulch makes in the spring, so it is an annual spring ritual for many to get out in the yard and slit a few bags of mulch open and get down and dirty. However, there is a potential problem lurking just below the surface. Wood takes time to break down in the soil, so if you are adding wood faster than it is breaking down, the mulch piles up over several seasons. You could take the extra step of removing a good portion of the old mulch to your compost pile, but that is too much work for my taste and scale of space. If you want to freshen up your beds in the spring, you need to spread a thinner layer and use a finer ground mulch, which increases the rate of decomposition. The type of material used will also affect decomposition rate. As an aside, your best wood mulch option for weed suppression and moisture retention is not ground up wood mulch but arborist wood chips, research is now finding. For the labor conscious (i.e. lazy like me) gardener, a new application of mulch need only be done every two to three years depending on conditions in your garden.
Once you learn a careful mulch spreading process, you will see bad mulch jobs just pop out all around you. You will feel mulch better about your work.
Josh Steffen, Horticulture and Facilities Manager