Home / FAQs


In the video, it creates sparks – are these possibly a fire risk?
Yes, while the spark itself has no thermal mass, the treatment wand can heat up and set fire to dry leaves. In dry conditions, our recommendation is to not treat directly onto dry grass, clear out dried leaves near target weeds, wet down the area with water before operation and check carefully for signs of smoldering before leaving an operating area.

What are the differences in effectiveness when the soil is dry, to when the soil and surrounding plants are wet?
Dry conditions are better as more energy is used treating the weed rather than heating any water in the soil. You might get an issue with the earth return not being able to find a route if your fixed earth is 25m away in extremely dry soil, however, we have even had success in summer on sand dunes.

How far down does the effect travel? So if you have a plant that has underground runners, how far/deep would the plants be controlled? eg, blackberry runners.
The RootWave Pro has been treating Japanese Knotweed in the UK which has a really deep root structure. We cannot control the path of electricity and therefore guarantee it will kill all the roots, but the longer you treat the weed, the more likely it is do the necessary damage, especially since the hypocotyl and meristem (control and growth centres) of many plants are found just below the surface of the ground.

Does the plant need to be in an active growth phase?
You can treat the weed anytime. It is best if the plant has plenty of water in its tissues, and some plants will change their water holding seasonally. We are developing our case studies to find the optimal timing for minimising the need for retreatments.

Can you cut back and then treat without waiting for regrowth? (eg cut down gorse and treat the cut stem to reach the roots?)
Yes, this would be our advice for large infestations as there is no point in wasting energy on the overall bush. We recommend for all weeds to be cut back to below gumboot height prior to operation, however, some regrowth may allow the operator to target the plant more accurately.

What is the effect on worms or soil biology such as fungal mycorrhiza?

The surrounding soil heats up less than on a hot summers day, so the soil biology will not be affected by the heat. As mycorrhiza are one cell thick if they are zapped with the electrical current it is likely to burst only one cell and do no further damage to the network, returning to earth through the soil water.

As we are only touching one weed at a time, the treatment area is still quite small, so the soil life will have plenty of opportunities to recolonise areas if anything did affect them.

Worms, due to their soft body contact with the soil water, don’t like the electricity, and are frequently seen coming to the surface and leaving the treatment area. Worms will be more greatly affected when the soil is wet. Unfortunately, some worms that come to the surface in wet conditions will die, although, in comparison, we think worms are worse affected by chemical sprays, rotary hoeing, stock compacting soil, or tractors.

What trials have been conducted?
Contact us for copies of the case studies. So far there have been detailed trials in NZ on lawn edges, agapanthus, acanthus mollis, Californian thistle, and woolly nightshade. We have more informal ‘before and after’ photos of various other key invasive weed species, including wild ginger, tradescantia and wild asparagus.

Are you a sustainable company?
We are trying to be, Hot Grass owns only electric/hybrid vehicles, we use 100% renewable energy to power our offices and cars, recycle and insist on all of our packaging being recyclable. We implement changes towards sustainability where practical, and we do choose green solutions wherever we have a choice. Our priority is on reducing the use of chemical herbicides, but we want to do it as ethically and environmentally friendly as possible.

The generator uses petrol, is that sustainable?
The generator does use 98 petrol, which is a fossil fuel. We think that on balance our system is pretty good, but this is an area that we would like to improve on. We did look at batteries, but they have their own environmental issues, and because of the power needed, we just couldn’t justify the cost. Hopefully, as battery technology improves we will be able to transition towards a clean, quiet energy source. In the meantime, we are happy knowing that it takes much less petrol to power our machine than it does to heat water for steam weeding. And other systems still use petrol/diesel, such as commercial weed sprayers or tractors – even on organically certified farms.

Is there an operator risk from electromagnetic radiation?
No, there is no comparable risk because the operator would not have continuous exposure to currents and therefore field densities are orders of magnitude lower than high voltage power pylons (according to our tech expert)

Comments are closed.