What information can you give me on flame weeding?
C.Z.VirginiaAnswer: Thank you for your recent request for information from ATTRA, the National Sustainable Agriculture Information Service. I am pleased to provide you with information on flame weeding.Flame weeding is a non-chemical weed control technique common among organic farmers. Flame weeding, also called flame cultivation, is dependant on propane gas burners to produce a carefully controlled and directed flame that briefly passes over the weeds (Diver, 2002). The intense heat sears the leaf, causing the cell sap to expand and disrupt cell walls. Foliage that retains a thumb print when pressure is applied between your thumb and finger has been adequately flamed. The flamed weeds soon wilt and die, usually in one to three days.Weeds are most susceptible to flaming when they are seedlings, 1 or 2 inches tall. Broadleaf weeds are more susceptible to lethal flaming than grasses. Grasses develop a protective sheath by the time they are approximately 1 inch tall and may require a second flaming. Repeated flaming can likewise be used to suppress perennial weeds such as field bindweed.Flaming on dry, sunny days is recommended (Daar, 2002). Weeds growing in dry areas tend to respond more quickly to flaming than those growing in moist habitats, perhaps because available moisture gives plants more resistance to the heat. When dealing with large areas of weed growth, work in sections, so that areas where weeds have not been flame-killed provide effective fire breaks – just in case some unseen dried material becomes ignited. Green plants undergoing flame-treatment rarely ever ignite. Most flame weeders are designed to not radiate large amounts of heat. Their purpose is to sear the leaves of plants (weeds) in order to change the protein structure of the plants. As a result, stress is what kills the weeds, not torching them. Due to the design and purpose of flame weeders, there is generally not enough heat produced to penetrate the soil and effect soil life. As stated above, timing is everything. While most articles focus on the weed control benefits of flaming, this technique also has other pest control applications (Daar, 2002). For example, potato plants up to eight inches (20.3 cm) tall can be flamed to kill Colorado potato beetles, Leptinotarsa decemlineata, without causing undue damage to the potato plants. Flamers can also be used to incinerate fallen fruit and mulch that harbors over-wintering spores that cause powdery mildew, brown rot, and other plant diseases. Given their versatility, flamers appear to be very useful garden tools – particularly for those seeking alternatives to toxic materials.ATTRA offers two publications on flame weeding; one for vegetable crops and the other for agronomic crops. Both of these publications are available online at the links stated below. You can also request a hard copy of these publications by contacting ATTRA by telephone at 1-800-346-9140.1. http://attra.ncat.org/attra-pub/flameweedveg.html2. http://attra.ncat.org/attra-pub/flameweed.htmlReferencesDaar, Shelia. 2002. “Flame Weeding in the Garden.” Brisbane: Gamaco Pty Ltd, Retrieved Feb. 9, 2007http://www.gameco.com.au/index.php?idp=26&mod=pageDiver, Steve. 2002. Flame Weeding for Vegetable Crops. Fayetteville: ATTRA.