Q. Hi, We enjoy your column and your helpful information. We would like to see you discuss the pros and cons of weeding with a blowtorch. We have seen people doing it. Can it be done in areas where you have landscape paper and bark surrounding plants you wish to keep? How about in areas where there is landscape paper covered with gravel? Landscape paper, as we know, does not keep out all the weeds. Thanks for the information. Dick and Jan Swanson – Olympia, WA
A. Blow torch weeding is essentially has evolved into a long handled tool that connects to a propane tank and allows the use of heat to scorch and dehydrate weeds. Many people think that the goal is to burn up the weed. The objective is the have the flame close enough to allow the flame to heat up the air surrounding the weed. This is especially useful in the cracks of sidewalks or against houses etc. Industrially I have seen specialized machines that run through the rows of corn and killing weeds between rows. Common sense dictates that there is risk to using a torch weeder where flammable mulch is present. But as I mentioned the flame only needs to get close enough to the weeds to scorch them. It is plausible that you could use it around bark mulch if the flame doesn’t contact or overheat the bark to the point of combustion before drying out the weeds. Weed fabric should be protected by a gravel mulch. I should also point out that the torch weeder is great on annual weeds or other weeds that have not formed underground storage organs. Older perennial weeds may resprout from underground structures after they are scorched back. For example dandelion could resprout from its underground taproot after the top is scorched back.