Microflora composition and antibacterial effect against Escherichia coli of plant extracts from different parts of Lavandula angustifolia and with different solvents were analyzed to determine variants to be used as microbial additives for enrichment with beneficial microflora, decontamination and deodorization of composts contaminated with E. coli. The highest total quantity of microorganisms was found in the decoction variant (whole plant and roots), and the lowest in the tincture variant (whole plant). The quantity of non-sporulating bacteria predominates in most variants. A significant increase of actinomycetes was found in the tincture and medical vinegar variants. The acidification of the environment leads to an increase in the quantity of mold fungi in the medicinal vinegar. Antibacterial effect against Esherichia coli for three tested strains (NMIMCC 3397 (WDCM 00012; ATCC 8739), NMIMCC 3398 T (WDCM 00090; ATCC 11775), NMIMCC 8905 (ATCC 35218)) was similar for the individual plant parts and the same for variants with whole plants. Lavender extracts, medicinal vinegar variant (individual plant parts and whole plant), as well as a decoction variant with a whole plant, showed stronger antibacterial activity against Escherichia coli. The concentration of all parts of the plant in "whole plant" extracts increased antibacterial activity compared to extracts with a concentration from a single specific part of the plant (roots, leaves, stems). Antibacterial activity against Escherichia coli remained lower even when whole plant was used for medicinal wine and medicinal oil variants. The choice of solvent probably has some effect on the diameter of the growth inhibition zone. The addition of Lavender extract (decoction variant, whole plant) to compost variants increased the quantity of non-pathogenic microflora in them. At the same time, the composts were decontaminated from the presence of Escherichia coli. The composts smelled of soil and lavender. The antibacterial effect of the lavender extract (decoction variant) against Escherichia coli strongly positively depends on the quantity of non-pathogenic microflora in it and in the composts after its application. The studied lavender plant extracts (best variant decoction, whole plant) can be applied as microbial additives, disinfectants against Escherichia coli and deodorizers of composts.