The results of the investigation of Perilla frutescens (L.) Britton growth, vegetation rhythmic dependence upon meteorological factors is given here. Experiments were carried out in 2001 – 2005 during vegetation period at Kaunas Botanical Garden of Vytautas Magnus University. Object of investigations - Perilla frutescens (L.) Britton a medicinal, herbal immunomodulator, annual herbaceous deadnettle family (Lamiaceae Lindl.) plant originated from Asia passes all development cycle in middle Lithuanian climatic conditions. P. Frutescens vegetation length on the average is 167 days. Earliest initiation of vegetation and optimal climatic conditions for growth are when HTC=1,60-1,80, that is excess heavy humidity. Optimal climatic conditions for massive flowering and seed ripeness are when HTC=1,20, then massive flowering starts 10 days earlier and Lasts for 25 days. Strong correlation interdependence was established between massive flowering and HTC (R2=0,9406). After the investigation of P.frutescens terraneous parts (high, relative plain area) consistent patterns of vegetation rhythmic, the optimal harvest time, which determines raw material’s quality and quantity, was established, by using mathematical – statistical methods.