Flame has been used on many occasions to kill weeds. Propane torches have been used by hand and larger flame weeding devices have been towed behind tractors. It is not in question that weeds can be killed in this way.
I tried an electric heat stripping device which was meant for removing paint. It worked all right for young tender weeds but would be very slow if you are trying to use it to kill a big patch of poison ivy. Much more heat is required in the name of labor efficiency. I've also used a propane tiger torch which is quick and effective but it consumes an expensive fossil fuel and catches everything in sight on fire.
So this has led me to yet another possible incarnation of the rocket stove .
If a small rocket stove were mounted on a garden wagon it should be possible to use the effluent to scorch the leaves of weeds. The stove would be allowed to completely consume its fuel at which point the effluent could be sent down some sort of flexible, insulated pipe. It may be necessary to drive the hot gas with a fan. With propane torches, no heat is produced until the gas leaves the rubber hose. With my theoretical device that heat must travel through the pipe. So this would call for protective gear which would include gloves, good boots and flame retardant clothing. And it would require some sort of superduper non-flammable and insulated hose. With all of this in place I could see using this device to kill not only weeds in the garden but also poison ivy, invasive cacti, kudzu, horse tail or any other problematic weed that tends to spread and take over. Many invasive plants have thorns or toxins which make them difficult or dangerous to remove. You would not want to use this device against the occasional weed that sprouts up amongst your prize-winning roses since there is bound to be some collateral damage .
One advantage this system would have is that no actual flame would emanate from the device and therefore you would be less likely to ignite dry leaves and other debris.
An alternative to the mini rocket stove plan could be to use charcoal and or wood chips or other small firewood in a cage which would be at the the very end of the flame wand. A battery-powered fan would drive air through a pipe to keep this stuff burning and to blow the heat in the right direction. This would be a much simpler and lighter device but it could definitely not be used when there is a chance of catching dry grass or leaves on fire. During my hot dry summer I wouldn't attempt this. I'm surrounded by logging slash which burns if you look at it wrong I suppose hot water or steam could also be directed at unwanted plants and undoubtably the steam would be more effective but also more dangerous for the operator.
I don't envision a device like this in every suburban toolshed but I can see it being very useful for larger homesteads and organic growing operations as well as for the maintenance of roadsides.
My road is half a mile long so that means I have 1 mile of road side weeds to experiment with. The only plant that I consider problematic in that zone is Scotch broom but there's also nothing else I value within 2 feet of the roadside so it's a good spot to conduct experiments.
I'd be interested to hear what others have done in using heat to control weeds. Also does anyone know what sort of hose could handle 1000° rocket stove effluent?
Let's examine the possibilities. No one has ever been successful in dissuading me from something that I'm fixated on so no point telling me that fires are dangerous.
posted 9 years ago
I thought flame (and steam) were useful on annuals but not so much on perennials, esp ones that are well established (I guess if you got a perennial seedling you'd be ok).
Location: Victoria British Columbia-Canada
posted 9 years ago
With many plants it's not necessarily to get an outright kill. If a quick torching or steaming can destroy the leaves which it hits this may be enough damage that the plant becomes vulnerable to insect attack, water loss etc. If you have desirable plants which are adjacent they will have a chance to outgrow the damaged weeds. In controlling scotch broom on a section of road I made no attempt to kill the plants. Instead I lopped off most of their branches and used them as mulch around young trees. Those young trees quickly outcompeted the broom for sunlight. Problem solved.
Location: Victoria British Columbia-Canada
posted 6 years ago
The largest agricultural fire around here in recent years was caused by ---------- wait for it ----------------- A flame weeding device. This happened about a year after I started this thread. Last summer I tested plain hot water from the kettle run through a plastic watering can. It warped the tool but also killed or at least badly damaged broad leafed weeds. Grass required so much hot water that any useful plant would also be damaged. This leads me to conclude that a light steaming or hot watering might serve to temporarily reduce broad leafed weeds in grass. I'm not sure that this is a good thing.
Hot water easily kills many little weed seedlings. The safest and most effective way that I can see applying the hot water would be with a pump pressurized weed sprayer. This is much safer than steam pressure. My sprayer is made of hard plastic and I don't want to ruin it. A metal one with an insulating sweater should handle the heat.
"Weeds" are the plants which grow when the nutrition and microbiology in the soil isn't good enough to grow what you want. When you pour hot water on the soil, you are killing the microbiology and starting over from a soil building perspective. I would recommend that you look into compost tea brewing and application to build up the soil and work to get what you want growing there and crowding out what you don't.
Weeds grow just fine in my super rich, near perfect soil.
This thread is about controling roadside and other weeds using flame, steam and hot water. As stated in the initial post, I won't be talked out of this. It's not something I'm married to, but I plan to exhaust the possibilities and report my results.
I have no intention of pouring hot water deep into the soil. A light spraying or steaming of the leaves does the trick.