For an update on this article see: Weed Burner, Part 2
Until chemicals began being used around the 1950s, weed burners were an important means of controlling weeds in agriculture, but today have almost been forgotten. Above is a picture of the weed burner I use.
Even though weed burners have not been widely used for a while now, the underlying technology of gas burners has improved dramatically in that time. Modern gas burners are much hotter and more efficient.
The weed burner shown above is one of the smallest models that will connect to a propane bottle, and the flame is shaped in a point. They can also be purchased in even smaller models that use a canister of gas similar to what a camping stove uses. Flames can be shaped in a point for use close to crops or wide intended to be used to cover large areas quickly. Sizes range up to tractor size that burn several kilos of propane per hour.
In Europe, some organic farms have been using weed burners where the flame heats a ceramic plate, which in turn burns the weeds. This is the so called infra red weed burner. The advantage of this is you don’t have an exposed flame, and the risk of starting a fire is less.
Okay, moving from farms back to gardening. There are circumstances in which it can’t be used. It is an exposed flame, and you can’t use it in a dry climate or around flammable materials. This makes it hard to use at the same time you use mulch, because most mulch is flammable. It also does not work against established weeds, as the only thing it does is burn the leaves off which just grow back again.
What is it good for? It works very well against weeds up to and including the cotyledon stage. For example if in the spring, your garden gets dusted by seed from dandelions or other weeds and they start sprouting, they can all be quickly destroyed with a weed burner. It will also destroy unsprouted seeds. If you have some compost that has been contaminated with weed seed, it can be spread out to a thickness of about 1 cm, and burned with the weed burner. Or you can just pass the flame over the top your compost pile to kill any seeds that may be there.
It is very easy to cover a large area quickly. My weed burner will cover about 100m2 (1000 ft2) in about a half hour, but there are circumstances when it takes longer like the ground is frozen or cold or there is a special problem that is being addressed with it.
The weed burner can be helpful right after plowing or rototilling the ground, because sometimes seeds are exposed and burning the pieces of exposed roots can help weeds from re-establishing themselves in the ground.
If you have a patch of established weeds, that you don’t have time to take care of before they go to seed, the weed burner can be used to slow their growth for a few days by burning the tops of them off. Of course this can also make them more difficult to dig them up when you finally get around to it.
In the last few weeks I have been using the flame to burn some things in the garden that would otherwise be more difficult to remove, like patches of dried out grassy weeds.
My garden is very large, about 1000m2 (10,000 ft2), and I plan to expand it in the coming years. The ground is also hard clay. Both of these things make it difficult to remove weeds under any circumstances, and in general I have a major problem with weeds. I can imagine if these things were not true, a weed burner would be less useful.
Having said all of this, I am really happy with it. It has become one of my favorite gardening tools. There is a reason why chemical weed killers became more popular, they do work much better, and this tool is certainly not going to solve all of your weed problems. It is however a great tool to use together with other organic methods for controlling weeds.