How much mulch is in safety deposit boxes across America? None, you say. I believe that's true, because we as gardeners purchase mulch to perform a function: that is, chiefly to accent our gardens, not to hide in some dark place where it cannot be seen. Consequently the longer mulch performs its function, the greater value mulch is to us. How then, can we make our mulch last for three years?
A lasting mulch bed begins with a properly engineered particle size. Mulch that lasts is intentional in how it is formulated, beginning with the size and the shape of the particles which make it up. If you were designing mulch, this is where you would have started, right? Well we heard you mention it and so we started there as well. In order to get the particles to lock together, we have to make this possible -- or even better, probable -- by inviting the particles to interlock. We do this by classifying the particle in sizes. Because we separate all of our mulches by size, we remove all of the very small particles from that will unproductively occupy pore space. By doing this, we leave voids for larger fibers to slip into and form a woven mat. This holds true for larger particles as well. When you do not remove larger particle from mulch, they will fail to find a large size pore to settle down into and consequently float atop the mulch bed, leaving even a large particle vulnerable to wind movement. By classifying the particle fibers and aiming for uniformity, our mulch maker ensures the greatest odds of the mulch interweaving itself together and matting down to the location it was intended for. This is a very important first step in determining the life of a mulch layer.
A second consideration in making your mulch last for three years is the application of an adequate depth. If we have designed a fiber particle that is capable of interlocking with its counterparts, then it only makes good sense that we would lay an adequate depth for this to optimize itself. The depth of your mulch bed will vary depending on the size of the fiber particles that the mulch you have chosen. You may have already thought this through from the previous paragraph, but let us take this to its logical conclusion. If you have chosen a mulch with particles that are 3” in length, then it makes good sense that if the total depth of fiber particles is less than 3" you compromise the staying power of the mulch bed. We can say this is a fact because, for every bed of 3" mulch with less than 3” depth, the particles that make up our mulch blanket are less probable to be in a vertical position, and more probable to be at an angle that is closer to horizontal. A 1.5” layer of mulch consisting of fiber particles that measure 3” is very likely to be found in the position with most of the fiber particles lying flat or horizontally. If the vast majority of particles are lying horizontal rather than interlocking at an angle, then we have left the makeup of the mulch bed vulnerable to being blown by the wind.
In contrast, when we apply a layer of 3” of fiber particles that are 3” in length, then we have wonderful odds of those particles being able to access the greatest number of pores in the mulch bed and consequently lock together very nicely.
This is not to say that we have to apply 3" of fresh mulch. If there is some old mulch present which has the same physical characteristics of the fresh mulch, then we need only to apply an amount that will leave the total depth of mulch at the recommended depth for our particle size.
This may be the best time to bring up the subject of landscape fabric in the application of mulch. Although using landscaping fabric is a matter of personal preference, I wish to raise this question: Are we compromising the bonding of our mulch blanket with the soil when we utilize landscape fabric? I encourage you to ask this question as you interact with other gardeners. Of late, I have found a growing number of mulch users who are firm in their conviction that fabric or weed barrier is best used only in the application of rock in a landscape. After pressing several of these gardeners on why they reserve landscape fabric only for rock covered areas, they responded with reasons which include: #1 the biology of the soil is able to interact with the mulch layer more easily and over a time period of several years this contributes to the overall tilth improvement of their garden beds, and #2 the ability of the mulch to lodge its fiber particles into the soil zone greatly aids in retaining the mulch in place for a substantially longer amount of time. This last reason is especially true for sloped areas. The question that I invariably enjoy bringing up is one of weeds. I ask, how much greater is your weed pressure in comparison to mulch beds utilizing landscape fabric? To which most respond, an adequate layer of mulch serves as a weed suppressant in much the same manner that a fabric would. Landscape fabrics are not infallible in their suppression of weeds. For example, a persistent weed will often times find a seam or an edge of the landscape fabric. This event will require a gardener's attention at some point, much the same way that a persistent weed would on occasion require the attention of a gardener who applied a liberal mulch layer.
The final factor in making mulch last for three years is the color endurance. Color is one of the biggest reasons that we as gardeners use mulch as a tool. Color is an invaluable asset when assembling a picture that is pleasing to one’s eye. Therefore, when the mulches that we as gardeners use fade in a seemingly short period of time (six to nine months), we lose a great asset in masterfully bringing all the details of our garden together. Color endurance is the motivating reason that Soil Rejuvenation Products increase the amount of colorant being used in our color-enriched mulches to 150% of the manufacture's recommended amounts. How do you feel about your mulch retaining its color through a second season, and even in most cases lasting into the third season? At Colorado’s high elevation, the UV light takes a high toll on all items outdoors. A thin layer of colorant leaves mulch fibers vulnerable to fading and breaks down on the surface where we want the color to endure. For this reason, when considering the purchase of color-enriched mulch, take the all-important step of asking about the colorant application process, in particular the amount of colorant that is used. Lowering an ingredient rate is a fast way to reduce production cost, resulting in not only a lower purchase price but also a lower value in color endurance for us, the gardeners.
Mulch brings many great benefits to my landscape, from soil fertility to the color coordination of my overall design. By choosing mulch that sticks around, I am also selecting a product that benefits my gardening budget because long-lasting mulch belongs in my yard, not in my safety deposit box.
by Brian Hoogland _______________________________________________________________________
Brian Hoogland is a fledgling writer and founding member of Soil Rejuvenation, Garden Bed Supply. He gardens in Berthoud Colorado.