View Full Version : Potting Soil Fire?!?

03-16-2005, 02:10 PM
A question for those who know more than me (the vast majority of you, I guess!)...

I went home for lunch today. I pull into the garage and I smell a fire. Smells like wood/sticks burning and it is very noticable. I grew up in the country and recognize the smell from the days of my youth. I immediately assume that some dummy who lives nearby is burning sticks/branches (illegal to do in my neck of the woods).

I step outside to try to determine where it is coming from and decide if I should intervene with the dummy or call the police. I realize that the fire is coming from my property!! My wife has a rather large pot sitting right outside of our garage. She puts something pretty in there every Spring. During the winter months, after the living thing inside has died, she sets the pot by the garage towards the back of the house (1-foot from the house). The pot has planting soil (little white beads in the dirt) and roots of the former living plant. Believe it or not, the darn thing was on fire about 1/2 way down inside the soil!

I thought, "Did some arse put a cigarette butt in here?" Our house is kind of off the beaten path and the garage is behind the house, so it didn't make sense that this could happen. I dumped the dirt out of the pot all around on the driveway. No cigarette butts. But lots of smoldering-like action going on. The one side of the plastic pot had two large "melted spots".

For the life of me, I cannot figure out how this happened. Kind of scary knowing that this happened so close to the house. Lord only knows what may have happened if I had not gone home for lunch. The pot was exposed to today's sunlight. I am thinking that the sun may have played a part, but how? Does potting soil catch fire like that? Does not seem like it should. The soil was not saturated, but it was also not 100% dry. The roots maybe? I am not sure how this could have happened either as the fire was 1/2 way down inside.

Anyone have any ideas as to what happened? Thanks. Just wish I could get that darn Talking Heads song, "Burning Down The House", out of my head!

03-16-2005, 02:19 PM
During this past year, the Colorado Springs Fire Department has investigated several fires caused by potting soil. In fact, just this year alone our community has suffered property losses in excess of 3 million dollars due to potting soil fires. Here are some unique factors to take into consideration.

Many potting soil mixes on the market today contain as much or more organic material as inorganic material. For example, potting soil can be made of shredded wood, bark, and/or peat moss with minimal amounts of what we call real soil (dirt). Styrofoam pellets, perlite and vermiculite are some of the other items that are often added to the soil mixture for aeration and water retention. In addition, many mixtures also include different types of fertilizers. Some fertilizers are oxidizers, which will make a fire that does start, grow at an even faster rate.

Potting soil mixtures are shipped moist and in plastic bags from the manufacturer. Most people use the soil in their planters in the Spring, then they forget about them once Fall/Winter arrives. Bacterial decomposition occurs within the mix that creates heat. This is the same principle that makes compost piles or bales of hay heat up. Although this principle, which is called spontaneous combustion, is usually found more often in climates containing more moisture; because water acts as a catalyst, these types of fires can also occur here.


03-16-2005, 02:33 PM
Thanks, z-a-g-g. That article hits the nail right on the head. I hate to be a Potting Soil Nazi, but no more potting soil for us! Wow. Just when I thought I had seen it all.

03-16-2005, 03:06 PM
That's pretty scary.