Whether in flower beds or around trees, the near-universal consensus is that having just plants and soil is far less advantageous than helping them with a layer of mulch or stones. The question, however, is which of these to choose. As is often the case, the answer to this is somewhat involved, as each has certain advantages and disadvantages. Moreover, the individual circumstances of the tree or flower bed might make one far more suitable than the other.
What are these advantages and disadvantages? And under what conditions might one be a better fit?
The benefits and drawbacks of mulch
If the mulch is organic, made from leaves and tree bark (as opposed to the rubber mulch found in playgrounds, which has an entirely different set of characteristics), there are several benefits from covering a flower bed or the base of a tree with mulch. For example, a 2007 article in the Journal of Environmental Horticulture notes that mulch:
Promotes tree growth
Organic mulch can boost tree growth by up to 67%, depending on the tree.
Temperature and water conservation
Mulch acts as a natural insulator, which has the benefit of reducing heat in the summer and in arid areas and conserving heat in the winter, reducing damage caused by temperature extremes. Moreover, mulch conserves water, reducing evaporation by up to 35%.
Protects soil from erosion and compaction
Organic mulch helps prevent erosion up to 85%, and because it tends to deter people from walking on it, it helps prevent soil compaction.
Adds nutrients to soil
As it is an organic substance, mulch will eventually break down and add nutrients to the soil. Mulch also tends to help plants resist damage from salts (such as those that may harm flowers and trees next to roads that are salted in the winter). Under the right circumstances, mulch can also reduce the effects of tree disease, keep out pests, and reduce weeds.
Two other benefits:
Installation and cost
Not a whole lot of effort is required to place mulch; it can pretty much be dumped right from a bag around the tree or into a flower bed. It is also relatively inexpensive.
Visual appeal
Many people consider mulch to be an attractive landscape addition.
By contrast, there are a few drawbacks to mulch, mostly involving what can happen if it is not properly installed. For example, mulch that is built up higher than 3 inches can damage plants (especially flowers). Because mulch does act as an insulator, if it is placed too early, it can keep a frozen ground from thawing out as quickly, delaying blooms of flowers. On the other hand, mulch that is applied too late in the year doesn’t as adequately prevent weeds as if it were spread earlier in the season.
One additional consideration: Mulch will eventually break down, which means it will have to be replaced. In the long run, the cost of mulch will compound through repeated replacement.
The benefits and drawbacks of rock
Rocks have some benefits and drawbacks of their own
Less maintenance and lower costs over time
Because rocks do not break down, and because they are too heavy to be displaced easily by wind and rain, rocks will not need to be replaced. At most, they require some touch-up treatments after a few years.
Weed prevention
Though rocks will require a weed barrier, once that is installed, they are very effective at preventing weeds.
Prevent erosion and less likely to hinder drainage
Like mulch, rocks can reduce erosion, especially from wind.
Moreover, since rocks have spaces between them, they tend to allow for easier drainage. Therefore, they might be the best choice for land with less-than-excellent drainage.
Rocks are not flammable
For people who live in wildfire-prone areas, the fact that rocks are fire-proof might make them a better option.
Visual appeal
Though obviously this varies from person to person, many people consider rocks to be an attractive addition, especially since they can come in a wide variety of sizes, shapes, and colors. This might make them preferable to mulch.
On the other hand, rocks have some considerable differences when compared to mulch: as rocks do not break down, they do not conserve water, nor do they add nutrients to the soil. In fact, rocks can sometimes affect the pH balance of soil, rendering acidic soil more alkaline (to the harm of some trees). Moreover, while rocks do not conserve heat in the winter, they hold onto the heat much longer in summer, which can further reduce the water available to plants.
Rocks are also much heavier and more difficult to install, at least at first. Unlike mulch, they require weed barriers and a metal or concrete barrier to keep them where they belong. Their initial expense is much higher (up to three times that of a comparable area covered with mulch), though that is a one-time expense. Finally, leaves and debris can drop and stick between rocks, requiring cleaning.
Mulch vs. Rock
Promier Landscapes can meet all the installation needs of both mulch and rocks, or our professional landscapers can simply assist with decision-making. Promier Landscapes has a wide range of services to offer businesses and residential homeowners, including tree care from certified arborists. For a consultation, fill out the form on the website or call (423) 872-2988.