Understanding and Mitigating Risks of Toxic Mulch

Understanding and Mitigating Risks of Toxic Mulch

With the burgeoning trend of gardening and landscaping, mulching plant beds has become a popular practice among enthusiasts. While mulch is widely acclaimed for its beneficial properties, enhancing the overall health and growth of your plants, and enriching the soil in the planting beds, it calls for certain cautionary measures.

Take, for instance, Ohio, where shredded hardwood bark mulch, a byproduct of the timber industry, is in high-demand. When logs are hauled into sawmills, the first step is to debark them. This resulting bark was once a major problem for mills until garden enthusiasts discovered its potential as mulch. Today, despite its valuable application, handling the bark efficiently remains challenging for some sawmills.

Sawmills tend to stack bark mulch heaps as high as possible to conserve yard space. This practice intensifies during winter months when mulch demand dips. In the bid to create these skyscraping piles, often front-end loaders are driven onto the pile. The weight of these hefty machines compacts the mulch, which eventually, can trigger problems for end-users if the mulch has been compacted excessively and stacked too high.

When the trees are initially debarked, the resultant mulch is quite fresh and necessitates decomposing before it's safe for plant application. This decomposition process mandates oxygen and air flow into the pile. Overly compacted mulch can choke the pile, inhibiting the necessary airflow as decomposition progresses. Consequently, as organic matter within the mulch ferments, it raises the internal heat. In some instances, the extreme heat, coupled with restricted heat release, could even ignite the pile leading to spontaneous combustion.

Equally concerning is the scenario where the mulch heats up, yet is unable to vent out the accumulated gases, thereby making the mulch toxic. This toxic mulch releases a strong, overpowering odor upon digging into the pile. Using this mulch around the plants releases the trapped gas, potentially burning the plants.

I've personally experienced this unforeseen danger twice. Both incidents involved the application of the toxic mulch around a Dwarf Alberta Spruce. The highly potent, reactive nature of the mulch caused one side of the plant to turn completely brown by the next day, it had been in contact with the plant for only a few minutes. Consequently, several other plants in the vicinity were damaged, needing replacement.

A vivid memory of this corrosive phenomenon was when a delivery of toxic mulch was dumped onto someone's driveway. As the toxic mulch slid out onto the asphalt, the released gas settled on the grass next to the driveway. This caustic gas, independent of the mulch devastation, discolored the green lawn to a parched brown.

Identifying toxic mulch can be challenging, given its almost similar appearance to the typical mulch, apart from possibly a slightly darker color. The distinctly oppressive and more potent odor differentiates toxic mulch from the healthy variety, but it's tough to describe this difference in words.

As a simple guideline, if you suspect your mulch may be toxic, apply a shovel or two around an inexpensive plant and wait for 24 hours. Use mulch from the pile's center, as it would contain the maximum gas concentration, while the edges most likely have let go of any gas. If the plants are unaffected after 24 hours, the mulch is safe to use.

The aim of discussing toxic mulch is not to raise an alarm, but to educate and avert possible damage to your garden or landscaping project. At my house, the toxic mulch burned off leaves and singed grass around the flower bed, rendering an unsightly look that seemed as if someone had literally torched the surrounding grass. It's a stark reminder that understanding your gardening materials is as essential as the practice itself.