Mixts. of 3 strains of Cyanobacteria (Anabaena sp. Trebon, Microcystis aeruginosa MKR 0105, Anabaena variabilis) and 2 corn. biostimulators were added to soil used for growing Sida hermaphrodita L. Rusby plants at temp. varying over a wide range (from -5 degrees C to +40 degrees C) applied at 3 week intervals (20% soil moisture) and excessive hydration (60%). Foliar application of Cyanobacteria mixts. and biostimulators significantly reduced the negative influence of hydrothermal stress and a positive influenced on the growth and physiol. activity of plants, increased the productivity of the plant, and can reduce the use of chem. fertilizers and pesticides.