The Value of Mulch

Anyone who has spent even the smallest amount of time gardening or maintaining plants probably already knows much of the value of mulch. My dad always seemed to know the value. But for him, I think it had to do with giving his children the character-building task of spreading hundreds of bales of pine straw on a Saturday morning. There was no reason to sleep in late---the task would be completed at my leisure. Despite the common familiarity of mulch, I am continually surprised by the amount of times I have seen weekend gardeners and landscape professionals underutilize or misuse this natural tool. While many people enjoy the “maintained” look of mulched plant and tree beds, there are several other substantial benefits including weed control, moderation of soil temperature, soil moisture retention, tree protection from mowers and weed eaters, and the addition of organic material to the soil.


We often think about mulch as just shredded bark or pine straw, but there are many of other mulch materials. Shredded leaves, compost, wood chips, wheat straw, and grass clippings can all be used to perform the same basic tasks. Each has its own additional benefits and drawbacks, so the options should be weighed for each application. Occasionally, you will notice that river stone, gravel, and rubber mulch are used in lieu plant-produced mulch. My advice:  Avoid these. They are sold under the premise that they don’t breakdown and will never have to be replaced. Unfortunately, that is the very reason they should not be used in most situations. They will never add any organic matter and nutrients back to the soil, and thus creates a constantly depleting shortage for the plants. Besides that, it just looks ridiculous.   


One of the most common mistakes I see people making is putting too much mulch around a shrub or tree.  Although it can depend on soil types, 3 to 4 inches of mulch will usually be enough to optimize the benefits. Also, the mulch should be kept off the trunk of plants. When accumulations of mulch are piled against the trunk, excess moisture can invite diseases and pests. It also becomes a great home for rodents that burrow and feed on the bark and cambium layers of young trees. A few weeks ago, I saw a municipal landscape crew piling pine straw almost two feet high around a tree. Don’t be that guy.


With our recent drought in central Alabama, it’s easy to see the benefit of moisture retention that mulch provides. Uncovered soil will quickly lose moisture in a matter of hours. Reduce your consumption of irrigation water by keeping a good layer of mulch around plants throughout the entire year.


One other benefit of mulch that is often overlooked, is its ability to limit soil erosion. I recently went to a property where a homeowner was looking for a solution to stop erosion on a wooded hillside. A particular area had been stripped bare of leaves and tree liter to appear “clean and kept”. Consequently, the topsoil was eroding and many tree roots were being exposed. Not more than fifteen feet away, the ground remained intact because of the untouched leaf litter. The solution was simple: Leave the leaves! Mulch not only protects plants, but it stabilizes topsoil and prevents erosion. Straw mulches are the best types for hillsides because they form an interlocking layer that doesn’t allow water to wash it down the slope.


Now that most of the leaves have fallen, it’s a great time to inspect your property to look for mulch that’s too thin or completely biodegraded. Consider adding mulch to protect your plant investments, reducing irrigation costs, and limiting your weeding.


Cahaba Design Studio is a landscape architecture studio located in Birmingham, Alabama that provides landscape design, land planning, and ecological design. As a division of Richter Landscape Company, the design studio is experienced in native plants, gardens, arboriculture, land preservation, and wildlife habitat design.