After responding to an unusual call, the Gravois Fire Protection District is cautioning home and business owners about the fire risks of potted plants.
Over the past weekend, GFPD personnel responded to a report of a planter that was smoldering, according to Captain Bob Forbes. While there was no damage to structures or persons, the district is warning people about the risk of possible accidental ignition of a structure from potted plants.
According to an article by insurance technology writer Michelle Tremblay, a higher than average number of fires over the last several years are being caused by potting soil catching on fire. Some of these fires have been serious.
The trend is mainly caused by cigarettes. Due to bans on indoor smoking and other factors, more people are smoking outdoors where there is often no ashtray or receptacle for cigarette butts. In these cases, people will often butt out in a nearby patio planter.
Occasionally, however, the potting soil can also self-ignite in cases where the soil gets completely dried out in neglected planters, especially those in plastic pots that get overheated by the sun.
Potting soil poses a fire risk due to its high amount of inorganic material that ignites easily. Many potting mixes sold today contain little or no actual soil, according to the article by Tremblay. They are instead made up of materials, such as sphagnum peat moss, vermiculite, perlite, aged composted shredded wood or bark and even styrofoam pellets, that are designed to absorb and retain water and aerate the soil.
Many people tend to planters in the spring but may forget about them at other times of the year.
If allowed to dry out, the potting material can act as a heat absorber. Combined with temperature build-up from bacterial decomposition and a certain level of heat and humidity, the soil can spontaneously combost, similar to compost piles and hay bales. Different fertilizers in the potting soil can act as oxidizers and add fuel to the fire.
While the potential for self-ignition in planters is relatively low, a cigarette butt in a dried out planter is much more likely to cause a problem.