It wouldn’t be far out to think that most people have or have had a potted plant in their home. But how many people know about a threat that’s believed to occur if they’re not watered?

The Jordan family from Timberville, Virginia, learned this the hard way after they let a potted plant on their back deck dry out.

As KFOR reports, 13-year-old Matthew Jordan was inside his parents’ home when he saw smoke coming from the back deck. The family rushed over to see the deck on fire.

According to WHSV in Harrisonburg, Virginia, the vinyl siding, a cooler, and a potted plant were completely engulfed in flames. Matthew told the TV station:

“I looked out this window, and I couldn’t see anything,” said Matthew Jordan. “I was used to seeing the picket fence. It was really scary …”

His father, Brad, had no idea what could’ve caused the fire to start. He told WHSV:

“I saw the deck was on fire and the side of the house was on fire, and I couldn’t fathom what could’ve caused this,” said Brad Jordan.

Capt. Joe Mullens of Rockingham County Fire and Rescue, however, had an idea: the spontaneous combustion of the potted plant sitting on the back deck.

Screenshot/WHSV

A plant the Jordans said they had for more than a year.

Mullens explained:

[…] know that it is still an organic material and it’s going to go through a natural breakdown process and generate heat. When you allow it to dry out, and it hits a certain low moisture content, it will spontaneously combust,” he said.

The fire and rescue captain advised keeping plants in ceramic or clay pots instead of plastic, replacing old mulch and soil, and keeping the soil wet.

According to KFOR, firefighters also warn against disposing of cigarette butts into potted plants which can cause the peat moss in the soil to ignite.

As for Brad, he wants other families to know what they could be dealing with when they have a plant potted in soil:

“I just think that people need to know how flammable this stuff is,” Brad Jordan said. “We didn’t know it, and we learned the hard way. But I like to think we were fortunate that we were home and were able to put it out.”

“Nobody thinks this could ever happen, but it did,” he said.

In 2006, Consumer Reports reported an alert issued by the Wisconsin Department of Agriculture, Trade and Consumer Protection about the hazards of potted plants.

A Wisconsin man had discovered the plastic container of his potted plant, and the table it was sitting on, completely melted after returning home from a trip. The man sent the remains to the department wondering if it had spontaneously combusted.

According to the article, the department did find a cigarette butt in the ashes but also discovered that commercial potting mixtures were comprised mostly of peat moss which is highly flammable when dry.

Another report issued at the time also found that many potting soil mixes were made of very little real dirt, instead containing shredded wood and bark — also flammable.

At the time, the executive director of the Mulch and Soil Council acknowledged that placing something hot into a dry planter could cause it to ignite, although “a bunch of dead plants in the pot is not the objective of most gardeners.”

In 2012, WHOTV in Des Moines, Iowa, reported that Des Moines firefighters were called to extinguish a blaze determined to have been caused by a large wooden pot filled with mulch and dead flowers.

Investigators ruled the mixture had spontaneously combusted. Months earlier, fire crews in the area responded to a similar call when wood chips and mulch spontaneously ignited at an Iowa playground.

In the case of the fire at the Jordan home in Virginia, investigators ruled the cause was spontaneous combustion.

However, Garden Myths questions the concept of spontaneous combustion altogether:

The point of ignition for dry peat moss is 260 °C or 500 °F (ref 5). This means that for spontaneous combustion to happen the peat moss in the pot would need to heat itself up to 260 °C. Note that this would be higher for wet peat moss. To put this into perspective, water boils at 100 °C.

Have you ever touched your planter or soil in the heat of summer and been burned by it? A temperature of 80 °C (175 °F) can cause severe burns in less than a second.  The pot needs to become 3 times hotter than this before the peat moss would ignite on its own.

Garden Myths concluded:

Peat Moss can not become hot enough on its own to spontaneously ignite.

There does not appear to be consensus on the issue, but as we head into summer it seems like a good idea to check on potted plants regularly.

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