The goal of the current study was to compare the chemical composition of the roots, shoots, and leaves of wild-growingEryngium maritimumL., and of in vitro and in field-cultivated plants in Latvia. The essential oil yield obtained by hydrodistillation ranged from 0.14% to 0.54%, while analysis of the chemical composition using GC-MS revealed a total of 44 different volatiles, with differences in the types and amounts of volatiles between the leaves and roots. Using 96-well plate techniques, the concentration of total phenolic compounds, saponins, and sugars in the aqueous ethanolic extracts ofE. maritimumwere assessed, along with their capacity to scavenge stable DPPH radicals. Extracts from roots had a lower concentration of total phenolic compounds compared to those from the leaves of wild grown and cultivated plants but did not differ from in vitro shoots. Root, leaf, and shoot samples of the same genotype from different growth conditions had approximately the same concentration of total saponins, while total sugar concentrations were higher in the roots. The growth conditions had a significant effect on the concentration of total phenolic compounds and antiradical activity, with differences that were significant observed between plant aboveground and belowground parts. Analysis using UHPLC-ESI-q-TOF-MS revealed 63 compounds, with amino acids and hydroxycinnamic acid derivatives (such as chlorogenic and rosmarinic acid) being the major compound groups that significantly differed between plant growth conditions. We also demonstrated that rapid screening of volatile compounds in in vitro plants using headspace gas chromatography mass spectrometry analyses can predict the formation of marker compounds in the same mericlones grown in field conditions. These findings provide valuable insights into the chemical composition ofE. maritimumand its potential for use in various applications.