Removing weeds

Countering weeds effectively is a major challenge in municipalities and agriculture. Chemical products are available, but they are often harmful to the environment and can only be used in a limited way in public spaces. Hot water can be used to remove dandelions, thistles, etc. without the use of herbicides – a much gentler process for the environment and for surfaces.

Removing weeds with hot water

Reasons for weed removal

Unlike cultivated and ornamental plants, weeds are plants that grow naturally without human intervention. There are many good reasons to control weeds: In agriculture, to protect crops. In towns and cities, to keep public spaces clean and tidy and to prevent damage to roads, open spaces and buildings.

Many weeds can spread extremely quickly and/or cause severe damage with their roots. They also have a negative impact on the desired aesthetics.

Weeds between paving stones

Overview of treatment methods

Thermal, mechanical and chemical methods can be used to destroy weeds. These methods differ, among other things, in terms of their environmental impact, sustainability and effectiveness. An overview of treatment methods:

 

Type of method

Hot water machines

Thermal

Hot foam machines

Thermal

Hot steam machines

Thermal

Hot air machines

Thermal

Flame devices

Thermal

Weed brush

Mechanical

Spray method

Chemical


Properties

Hot water machines

Up to 98 °C
Kill the parts of plants above ground and the roots below using hot water.

Hot foam machines

> 100 °C
Steam cleaner with additional foam production. The foam is used for insulation purposes and is intended to prevent the steam from cooling too quickly.

Hot steam machines

> 100 °C
Kill the parts of plants above ground. However, heat transfer from steam is nowhere near as effective as that from hot water. Roots are not effectively attacked.

Hot air machines

> 350 °C
Kill weeds using intense heat from hot air.

Flame devices

> 400 °C
The plants are heated using burning gas, causing them to die and partially burn.

Weed brush

Weed brushes and strimmers remove the plants from the roots.

Spray method

Herbicide is applied to the leaves using a spray unit.


Environmental impact

Hot water machines

Low

Hot foam machines

Moderate

Hot steam machines

Low

Hot air machines

Moderate

Flame devices

High

Weed brush

Low

Spray method

Very high


Effect

Hot water machines

Plants and roots are weakened and destroyed, including the seeds.

Hot foam machines

Plants are weakened and destroyed. Limited penetration.

Hot steam machines

Plants are weakened and destroyed. Limited penetration.

Hot air machines

Surface growth is destroyed. Limited penetration.

Flame devices

Surface growth is burned. Limited penetration.

Weed brush

The parts of plants above ground are removed using a steel brush. No penetration

Spray method

Herbicide weakens and destroys the cell structure of the plant down to the roots.


Noise exposure for users

Hot water machines

Low

Hot foam machines

Low

Hot steam machines

Moderate

Hot air machines

Moderate

Flame devices

High

Weed brush

Moderate

Spray method

Low


Special requirements

Hot water machines

Can be used on all surfaces, including critical and hard-to-reach areas.

Hot foam machines

Can be used on all surfaces, including critical and hard-to-reach areas.

Hot steam machines

Can be used on all surfaces, including critical and hard-to-reach areas.

Hot air machines

Ineffective in moist conditions.

Flame devices

Cannot be used in extremely dry conditions, ineffective in moist conditions.

Weed brush

Standard in public areas; achieves desired clean, smart look in towns and cities as the weeds are removed directly.

Spray method

Generally prohibited, may be used on paved and compacted areas only with special authorisation, certificate of expertise required.


Sustainability/effectiveness

Hot water machines

High

Hot foam machines

High

Hot steam machines

Moderate

Hot air machines

Low

Flame devices

Low

Weed brush

Moderate

Spray method

High


Application frequency

Hot water machines

Up to four applications in the first year, decreasing the following year.

Hot foam machines

Up to four applications in the first year, decreasing the following year.

Hot steam machines

4–6 applications.

Hot air machines

Application must be repeated about every 4 weeks.

Flame devices

Application must be repeated about every 4 weeks.

Weed brush

Application must be repeated about every 4 weeks.

 

Spray method

Up to four applications in the first year.


Overall assessment

Hot water machines

*****

Hot foam machines

**

Hot steam machines

***

Hot air machines

**

Flame devices

**

Weed brush

***

Spray method

**


Destroying weeds with hot water

Weed removal with hot water: Effective and environmentally friendly

The overview of treatment methods shows: Weeds can be removed effectively using various thermal methods. The principle of thermal weed control is based on a basic biochemical rule: Most proteins denature from a temperature of around 42 °C. This means that the proteins change, break up and are no longer able to fulfil their functions.

The heat required for this can be generated and converted in different ways: As a direct flame or indirectly via thermal radiation, as hot water or steam. Hot water is the only chemical-free method that also reaches the roots. Even if the roots are not immediately completely destroyed, the weed is further weakened with each application of hot water. If it is regularly applied right from the beginning, regrowth is impeded and the application frequency will significantly decrease as early as the second year. As a rule of thumb, three to four treatments a year are sufficient.

Tip: The right time to use this method

The best time to remove weeds is in the afternoon. The amount of water stored by plants varies depending on the time of day. It is best to start with the first hot water application shortly after the weeds have sprouted in spring. This is because as plants get older, they become more resistant to hot water.

Use of hot water high-pressure cleaners

The critical factor when removing weeds with hot water is the temperature: The hotter the water, the more efficiently the plants can be eliminated. Hot water high-pressure cleaners can offer a consistent water temperature of up to 98 °C, which is just under the steam limit and is therefore ideal.

Weed removers are ideal accessories. Depending on the size of the surface and required use, these vary in terms of working width and area performance.

Tip: Distance between nozzle bar and surface

The optimal distance between the nozzle bar of the Kärcher weed remover and the surface is between 5 and 15 centimetres. It is possible to work comfortably within this range without the weed remover touching the ground. It also means that the loss of water temperature as the water travels to the surface is minimal.

Removing weeds gently with hot water

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