Every year firefighters warn us about the dangers of space heaters, string lighting, fire pits and burning candles. These are serious hazards, but the fire experts are now adding potting mixes to this list.
Potting mixes are increasingly the root cause of house fires. Most of these fires are not the result of spontaneous combustion; they are usually started by individuals extinguishing their cigarettes in a pot filled with potting mix.
Because potting mixes often are referred to as potting soil, many smokers do not give a second thought to using a container garden or indoor potted plant for an ashtray. They do not think of dry potting mixes as being flammable. If they are not dedicated gardeners, they probably do not realize that “potting soils” are actually mixes of numerous flammable materials, such as peat moss, wood fiber, coconut fiber, chopped bark or compost. The potting mixes of today generally contain very little sand or real soil, but many do contain fertilizer. Some fertilizers are oxidizers that can lead to faster-burning fires.
Fire departments across the U.S. are starting to warn the public about the fire danger of potting mixes. Joe Terppening, Deputy Fire Marshall for the Kennewick Fire Department, indicates that in the past three years, at least 20 percent of local house fires were the result of cigarettes being extinguished in pots filled with potting mix.
So what can we do to minimize the hazard? Here are some tips from several different fire departments:
▪ While you and other members of your family may not be smokers, you may have guests who smoke. Provide an ashtray by each of your outside doors for a convenient and safe way for extinguishing cigarettes. An alternative to this would be placing a metal container (such as a metal coffee can) filled with sand by the doors and marked for this purpose.
▪ Many gardeners have container gardens close to their outside doors. During the growing season, fire is less likely when the potting mix is kept moist and the plants are well maintained. When a plants dies and dries up, it should be removed. During the winter when the pots are not being watered, it is advisable to remove the dead plants and store the containers away from the house.
▪ If you keep a bag of potting mix stowed close to the house so it will be handy, periodically add moisture to the bag to keep the mix from drying out. This also will make it easier to rewet when using it for planting. Also, keep bags of potting mix away from other combustible materials and fire sources, like barbecue grills and fire pits.
▪ Plastic pots melt and burn. When possible, use clay or ceramic pots for your planters.
▪ Live indoor plants are becoming popular again. Plant owners should keep the potting mix of most houseplants slightly moist in case someone decides to use a plant pot for an ashtray.
Soil-free potting mixes have been around for over 40 years, but I suspect this uptick in fires being caused by them is the result of more and more smokers being asked to smoke outside the house. This is better for the health of nonsmokers, but it has created a serious fire hazard.
Marianne C. Ophardt is a retired horticulturist for Washington State University Benton County Extension.