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.
Here at Wellfield, there are several next steps in the mulching process. After the bed is properly edged, the next step is to spread one to two inches of finished compost, as our hort staff member Tammy is seen doing in the image above. We do this to increase the percentage of organic content in the garden soil.
Next, staff spreads a two inch layer of double ground mulch. Our particular supplier grinds up a mixture of different wood products from hardwood trees to leftover RV material, creating a finer particulate product than a typical double ground hardwood mulch, thus eliminating impenetrable crusty, sun baked mulch. Using a mulching fork, mulch is placed in a small pile on the ground and spread with the flat part of the fork to the desired two inch depth. The recommended mulch depth used to be three to four inches, but research is showing some mulches at depths of three to six inches can actually retain too much moisture, creating waterlogged conditions. Often two to two and half inches is sufficient to get all the benefits of wood mulch. You will have to play around with what you typically spread to know what works for you.
Once mulch is forked in place (emphasis on placed and not flung), the mulch is given an additional smoothing with a leaf rake.
Lastly, a hard rake is used to compact the mulch along the bed edge to make sure none has spilled into the trench, which would cause you to lose bed definition.
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