A red pop of color among a sea of flowers looks enticing, but how does spontaneous combustion sound? A shocking piece of advice recently hit r/Gardening, warning hobbyists to steer clear of aesthetic mulch.
The Redditor urged gardeners to use caution with mulch — particularly colored mulch — and compost, as it could reportedly catch ablaze. They indicated that compacted materials let fewer gases escape, raising temperatures, and could interact with the dye chemicals to start a fire. The user also said that using water will not help if smoke is visible and advised dispersing the materials.
"Many people may not be aware of the very real issue," the user said.
"Can confirm," one person wrote. "I used to work in a lawn and garden shop and mulch fires were regular enough that we didn't even call the fire department and had a standard procedure for taking care of it."
While many people offered different perspectives and skepticism, posts like this start these necessary conversations so people can take proper care of their gardens.
Here are some facts: Mulch must be piled thickly or "cover a large and compacted area" to have spontaneous fire concerns, according to Homes & Gardens, in a report that consulted a fire chief. Mulch fires typically occur in hot and dry scenarios, and can be exacerbated by wind.
"These fires occur in hot and dry (and especially breezy) conditions where the depth of mulch and organic material is sufficient to decompose and generate its own heat," said Charles Moore, fire chief at Truckee Meadows Fire & Rescue in Nevada, according to Homes & Gardens. Moore said he had seen "a number of mulch fires that result from spontaneous combustion."
Spontaneous combustion is more of a concern for large, industrial piles of mulch and commercial mulch production, as some Reddit comments suggested. Based on a study it commissioned, the Mulch & Soil Council industry group says that spontaneous mulch combustion is "extremely unlikely … in a landscape application."
Influences such as stray cigarettes, local climate, and gardening layout also may contribute to the likelihood of fire. Discarding smoking materials in mulch is a particular concern, according to the Massachusetts Department of Fire Services. The department also points to regulations for applying mulch close to multi-unit residential buildings and for storing and manufacturing mulch "because large piles can spontaneously combust from the heat they generate."
The Redditor's claim that water won't help a mulch fire wasn't elaborated on and is debatable. One response speculated that the original poster meant water might not prevent the root problem of a mulch pile from getting hot. Meanwhile, Moore did recommend to Homes & Gardens that home gardeners "keep … material well watered and moist" to prevent fires.
The post also did not cite a source on the danger of colored mulch, though the National Fire Protection Association states that some tests have shown that different mulches may be more or less combustible.
Ultimately, dyed mulch isn't great for the planet, no matter how good it makes a garden look. The chemical treatments to craft the mulch can impact a garden's soil quality, though mulching naturally does offer benefits, including water conservation and weed suppression. Choosing natural, compost-friendly mulch can help support healthy ecosystems for pollinators and consistent yields — particularly when paired with native plants.
Rewilded yards are also low-maintenance, and because the plants are suited to their natural environments, you don't have to spend as much money on water bills. In fact, they may even raise property values because of their desirable beauty — something one commenter alluded to.
"Painted mulch is an atrocity regardless of fire," one commenter said. Another responded: "The red looks like an open sore."
Others suggested reading mulch bags carefully because it can be challenging to tell if mulch is red because of paint, iron oxide, or the type of wood used, like red cedar.
However, sun exposure will eventually make the colors fade, especially if made with natural ingredients. Having an eye over any garden is critical, and using natural mulches in a thin layer, along with native plants, is safer and better for the environment.
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