The following question was asked by a fern gardener:

"I have several containers where I grow ferns that require constant humidity. Some of these containers have colonies of liverworts, which I would like to eliminate. Mechanical removal is painstakingly difficult. I´ve been told that applying quaternary ammonium with a brush could be a solution. Has anyone had experience with this?"


Personally I love liverworts and have no experience trying to get rid of them. I love to look at them and imagine little gnome forests and think of how they are one of most primitive land plants, potentially very similar to the ancestors of ferns.

I am also a big opponent of using pesticides, especially for purely "aesthetic" reasons. The world could live better with fewer chemicals like quaternary ammonium being released into it.

The following warnings about quaternary ammonium are from the web page of Chemical Safety Information from Intergovernmental Organizations in cooperation with the Canadian Centre for Occupational Health and Safety (CCOHS):

2.1 Main risk and target organs

Quaternary ammonium compounds can cause toxic effects by all routes of exposure including inhalation, ingestion, dermal application and irrigation of body cavities. Exposure to diluted solutions can cause mild and self-limited irritation. Concentrated solutions of quaternary ammonium compounds are corrosive and can cause burns to the skin and the mucous membranes. They can produce systemic toxicity due to their curare-like properties. They can also cause allergic reactions.

2.2 Summary of clinical effects

Mild to severe caustic burns of the skin and mucous membranes can occur depending on the agent and the concentration. Other signs may include: nausea, vomiting, abdominal pain, anxiety, restlessness, coma, convulsions, hypotension, cyanosis and apnoea due to respiratory muscle paralysis; death may occur within 1 or 3 hours after ingestion of concentrated solutions. Haemolysis and methaemoglobinemia have been reported infrequently.

2.3 Diagnosis

Diagnosis depends essentially on prior history and presentation of specific signs and symptoms. These may include gastrointestinal symptoms, pain, burning sensation or local ulceration depending on the site of exposure and the concentration of the solution.

In addition they state:

"Repeated occupational exposure after handling quaternary ammonium compounds as powders or solutions can produce sensitization (Shmunes & Levy, 1972; Oritiz-Frutos et al., 1996; Placucci et al., 1996; Krogsrud & Larsen, 1997)."

I would add that the long-term impacts of many dangerous chemicals on the body and the environment in general are often either not known or are hidden from us by powerful corporations and the governments and media they control. Sensitization to one chemical can often sensitize one to many other chemicals. In addition exposures to chemicals that are damaging in the short term often cause cancers over time.

If you have pets, or enjoy seeing other living things around your plants such as birds or even invertebrates (as I do) then you should also consider their health.

I would suggest that if you do not like Liverworts you pluck them out of your flowerpots by hand. You said you have several pots where you see this as problem. I cannot see where adding a dangerous chemical would be seen as being better than taking a little extra time to do some work that ensures a healthy environment for all of us.