Using Flame Weeders for Garden Weed Control

The Pros and Cons of Weeding With a Torch

Gas-powered flame weeder on a gravel driveway
Gas-powered flame weeder on a gravel driveway

ClarkandCompany / Getty Images

Even in the best maintained, well-mulched, and densely planted yard, weeds are a constant reality. If you are tired of pulling weeds mechanically, or you want to avoid using herbicides, a flame weeder can come in handy. Before you light the torch, though, you should know that flame weeding has its limitations both in terms of the locations where it can be used as well as the types of weeds it kills. 

What Are Flame Weeders?

A flame weeder briefly exposes weeds to extreme heat up to 2,000 degrees F, just long enough to damage the plant tissue so that the plant dies. The plant is not burned in the process.

The tool consists of a torch or wand that is connected to a propane tank by a hose. There are different systems for the propane tank: torch flame weeders that can be hooked up to any refillable propane tank include backpack-style flame weeders, and rolling flame weeder where the tank is installed on a dolly. Flame weeders for home gardeners vary in BTUs between 40,000 and 100,000. 

Are Flame Weeders Effective?

Flame weeding is most effective on weeds no taller than one to two inches; the smaller the weeds, the better they work.

It kills only the above ground part of a plant, not the roots, which is why it is mainly effective for annual weeds. Perennial weeds can regrow from the leftover roots in the soil and usually require repeated treatment in order to be eradicated. Repeat the flame weeding every two to three weeks, or when the weeds have regrown, which will weaken them to the point where they won’t grow back. 

What Are the Benefits of Using Flame Weeders?

Using a flame weeder is physically easier on your body than mechanical weeding because it saves you from bending down and pulling or digging. It does not disturb the soil which means dormant weed seeds are not brought to the surface where they will start to germinate.

Unlike non-organic herbicides, a flame weeder does not contaminate; it is environmentally safe because it does not expose humans, pets, wildlife, ornamental plants, your vegetable garden, groundwater, and soil to toxic substances. 

A flame weeder is particularly useful for weeds that grow in sidewalk cracks and between patio pavers, as well as on gravel. For weeds that grow into garden fences, whether you can use a flame weeder depends on the flammability of the fence material. Non-coated metal fences such as chain-link or welded wire mesh can withstand the heat but wooden or vinyl fences won’t.

Before using the flame weeder on any fences or barriers, check the manual, as flame weeders vary in their BTUs (the amount of heat they emit).

Flame weeders work especially well for sidewalk cracks
Flame weeders work especially well for sidewalk cracks

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What Are the Cons of Using Flame Weeders?

The biggest downside of using a flame weeder is that, although the torch enables you to aim and target the unwanted plant, it is difficult to avoid singeing desirable plants as well, especially in densely planted areas such as a vegetable garden or a flower bed. 

If used properly, a flame weeder is safe for the person who operates it. However, it can still pose a danger for pets or children running about, which is a safety issue as you consider when and where the weeder can be used.

When Not to Use a Flame Weeder

Never use a flame weeder during a drought or in dry conditions, and keep a safe distance away from any dry, dead, or brown plant material that could catch fire. Also stay a away from houses and other structures that could catch fire.

Also, the municipality where you live may have issued a flame weeder ban. Before purchasing and using a flame weeder, make sure to check with your local fire department.

How to Use a Flame Weeder

Wait until after a rain, or, if the soil is dry, it’s a good idea to irrigate the area where you want to use the flame weeder; this will reduce the risk of ignition. 

Follow the manual to ignite the flame of your flame weeder. Run the torch over each weed in a sweeping motion and make sure to stay at a safe distance from the trailing hose between the tank and the torch. 

Touching the flame to each weed only for a split second does the job. If you aren’t sure you killed the weeds, wait until they have cooled down; the leaves will have turned from glossy to dull. 

Home gardener using a flame gardener in grass
Home gardener using a flame gardener in grass

ozgurcoskun / Getty Images

Does Flame Weeding Kill Seeds?

If you use a flame weeder properly—only on short weeds no taller than two inches—any weed seeds on the soil surface will also be directly exposed to the high heat from the torch and won’t be able to germinate.

On the other hand, if you are applying the flame weeder on weeds that have gone into seed, it will not necessarily kill their seeds.