Issue 7

The Four Components of Plant Flammability

In the firewise landscaping context, flammability refers to the ability of a plant to ignite and transfer heat and/or flames to surrounding plants or structures. Plants are flammable for different reasons; some plants ignite quickly, but also burn off quickly. Other plants are not easy to ignite, but can burn for a long time once ignited. Flammability is made up of four components:

• Ignitability—the length of time until a plant starts burning when exposed to a flame or other heat source
• Combustibility—how rapidly or intensely a plant burns: the rate of spread and rate of heat (or energy) given off from a burning plant
• Sustainability—the length of time the plant will sustain a fire
• Consumability—how completely the plant burns, or the quantity of the plant that is consumed during a fire

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