This article analyses the results of studying the influence of polymeric guanidine derivatives, namely polyhexa­methyleneguanidine chloride (PНMG), on land and freshwater plants. Gas chromatography was used to determine the soil – plant and water – plant transition coefficients. Methods of mass spectrometry and photocalorimetry were used to identify the PHMG in the samples. We investigated the toxicity of PНMG for freshwater flora in an aquarium on Vallisneria spiralis, Riccia fluitans and Chlorella pyrenoidosa. The results showed that even the lowest bactericidal concentrations of the preparation (10–3% or 10 mg/L) caused the death of test organisms within one to two days. One-time application of PНMG to the aquarium in dose of 10–4% (or 1 mg/L) did not cause any noticeable changes in algae during the 7 days of the experiment. The PНMG transfer coefficient did not exceed 0.1% for the system "water – algae tissue". Moreover, the initial concentration of the drug in the water decreased by almost ten times already during the first two days. PНMG polycation molecules quickly bind to dissolved in water organic and inorganic substances, suspended particles, microorganisms, etc. Flocculation causes a sharp decrease in the number of active "free" polycation molecules in water. The drug settles on the bottom of the aquarium and then is destroyed by bacteria saprophytes. Apparently, PHMG is included in their metabolism and serves as nitrogen source for microorganisms Pseudomonas putida, Flavobacterium columnare, Bacillus sp., Sarcina sp., Nitrosomonas sp. and Nitrobacter sp. At the same time, this study showed that the safe concentration of PHMG for hydrobionts in the water of natural fresh water reservoirs is 0.01 mg/l, or 10–6%, provided the drug is chronic. Ground plants are more resistant to the action of PHMG. They easiliy tolerate finely dispersed spraying with 0.3% aqueous solution of PGMG chloride in a dose of 0.5–1.0 l/m2. For Urtica dioica, Artemisia absinthium, Taraxacum officinale and Poa angustifolia the coefficients of transfer of the preparation from the surface of plants to internal tissues did not exceed 0.01%. And the coefficients of transfer of PHMG from soil to plants were in the range of 0.004–0.008%. We conducted environmental monitoring in Rivne region during 2011–2015. It showed that numerous cases of use of PGMG drugs for disinfection of various agricultural objects did not lead to any noticeable negative consequences for natural biocenoses. Consequently, we can assume that the preparations of PНMG do not pose a serious threat to the vegetative component of ecosystems. Migration of the drug is minimal in food chains in soil and water.