My “gas plant,” Dictamnus albus, is finally flowering for the first summer ever, and I am starting to worry: can it spontaneously combust? It’s planted close to the house. I remember stories from a couple of years ago about houses in Seattle catching fire because of sun or extreme heat igniting compost or soil in planters. Are there plants besides Dictamnus that are especially flammable?
Dictamnus is not called the gas plant or the burning bush for nothing. It is in the same family as citrus plants, and contains extremely volatile oils that can indeed reach a high enough temperature to ignite. In Defense of Plants blog describes this aspect of the plant, and asks why a plant might have this capability (to burn out competing vegetation, or merely an unintended consequence of oil production). Excerpt:
“If air temperatures get high enough or if someone takes a match to this plant on a hot day, the oils covering its tissues will ignite in a flash. The oils burn off so quickly that it is of no consequence to the plant. It goes on growing like nothing ever happened.”
Some gardeners amuse themselves and amaze their friends by demonstrating this flare of flame, but I highly recommend you not try it if your plant is up against your house!
You can read more about the flammable properties (and garden merit) of Dictamnus in the June 1995 issue of American Horticulturist. See the article “Ignite the Night” by Robert L. Geneve.
There are other flammable plants. Areas that are accustomed to preparing for summer fire season (such as Grants Pass, Oregon and Ashland, Oregon) have information about which plants are most (and also which are least) likely to ignite. The flammable list includes ornamental juniper, Leyland cypress, Italian cypress, rosemary, arborvitae, eucalyptus, and some ornamental grasses.
If you are concerned about the proximity of this plant to your house, you might consider transplanting it elsewhere in fall, though be aware that Dictamnus has a taproot and is not fond of being moved.