Follow-up on Last Week’s Post About Potting Soil Being a Fire Hazard

From reader Jim Borland:

Yes, nitrogen fertilizer can be used to make a bomb à la Oklahoma City bombing, though I doubt that the nitrogen fertilizer in Miracle Gro’s potting mix contributed much if anything to the fire that resulted from the insertion of a cigarette butt into the soil. What you missed in taking a picture of the package was the other part of the contents besides the fertilizer. All potting soils these days are made of synthetic products including those made by Miracle Gro. In the case of this particular potting mix it consists of forest products (shredded and chipped wood and bark), coir (shredded coconut husks), composts, peat, sphagnum peat moss, perlite and wetting agent.

All but the perlite and wetting agent are flammable, especially when dry. In this case the soil was undoubtedly not moistened as most soils are that have live plants in them. The nitrogen part of the fertilizer is contained within prills or small plastic coated spheres, here called Osmocote, that release nitrogen with each watering. After a couple of waterings the nitrogen is gone, leaving only the plastic capsule behind. Even with no fertilizer, this and other artificial soils are flammable, and care must be taken when located in a place convenient for snuffing out cigarettes. 

Author: Golden Real Estate, Inc.

Golden Real Estate is a prominent member of the Denver/Jefferson County real estate scene. Based in Golden, we service both Denver and Jeffco, representing both buyers and sellers. We're well known for Broker Jim Smith's weekly "Real Estate Today" column published in the Denver and Jeffco editions of the Denver Post's YourHub section each Thursday. The column also appears in several weekly newspapers and is archived at We have nine agents, all of whom are Realtors and EcoBrokers. Our office is Net Zero Energy since December 2017, and several of us drive electrics cars. Known for our sustainable practices, we accept polystyrene (aka "Styrofoam") for recycling, keeping 200 cubic yards per year out of area landfills.

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