Numerous scientific studies, in which beneficial effects are shown of silicon on plants, are proof of the growing interest in the role of silicon in terms of its influence on the growth and proper development of plants. Also they highlight the need to supply the substratum with this element during plant production. The objective of the research study was to tweak the method for preparing samples of plant material and to determine the content of  silicon therein with the use of total reflection X-ray fluorescence spectrometry. The samples of plant material,  which included lyophilized and dried leaves of common sage (Salvia officinalis), dried leaves of field horsetail  (Equisetum arvense) and dried leaves of stinging nettle (Urtica dioica), underwent an elemental analysis. The  samples of dried plants were digested with a mixture of concentrated nitric acid(V) and hydrogen peroxide in a  microwave mineraliser. The analysis of the silicon content in the samples was performed using a total reflection X- ray fluorescence spectrometer (TXRF). The silicon content in the common sage samples was 0.2 %, in the stinging  nettle samples – more than 0.5 % and in the field horsetail samples – ca. 1.4 %. In order to confirm and complete  the information obtained, the collected plant material underwent a microscopic analysis using a scanning electron  microscope, which made it possible to determine the elemental composition in the micro-area by means of a  secondary X-ray energy dispersion spectrometer. Microscopic photos were taken and an analysis was performed  of the elemental composition of samples of the plant material in the micro-area; the analyses performed  demonstrated that silicon was present in three samples of the plant material analysed: in conventionally grown  sage, in nettle and field horsetail.