Some Least-Toxic Herbicides
Herbicidal Soap is made from potassium salts of fatty acids derived from naturally occurring plant oils and animal fats. Contact with herbicidal soap damages plant cell walls, causing dehydration and tissue death. Soaps are broad-spectrum, non-selective, and work best on seedlings. Deep-rooted weeds and perennials will require repeat applications. Soaps break down completely within 48 hours and carry the EPA rating: IV. CAUTION. There is also an herbicidal soap for use specifically on lawn moss.
Glyphosate is a water-soluble salt that inhibits a plant’s ability to produce certain essential amino acids, thus hindering new growth. This is a nonselective, broad-spectrum herbicide with the EPA rating: IV. CAUTION. You may not see effects for 7- to 10-days. Not toxic for outdoor pets, however it is still important for homeowners to read the label and follow the instructions.
Glufosinate-Ammonium is a metabolic compound originally derived from a soil bacterium. It interferes with photosynthesis, killing annual weeds and even many perennial weeds in one to four days. It is nonselective and broad-spectrum; however, it affects only treated plants. It is biodegradable with an average half-life in soil of 7- to 20-days. It carries the EPA rating: III. CAUTION.