The effect of filtered torrefied wood powder as a plant growth retardant was evaluated. The filtered extract was manufactured using torrefied wood powder (Quercus serrata Thunb. Ex. Murray) and distilled water. The filtered extracts were used to create four solutions of varying concentration (1%, 5%, 10%, and 20%). Each solution was applied to various seedlings (Amaranthus retroflexus, Plantago asiatica, Echinochloa crus-galli var.) over the course of six days. Additionally, gas chromatography-mass spectrometry (GC/MS) was performed to investigate how plant growth was affected. The results indicated that higher concentrations of filtered extract delayed seed growth more than solutions of lower concentration. Additionally, the GC/MS analysis of the filtered extract of torrefied wood revealed one phenolic compound and two different types of furan compounds. This study investigated the active components of torrefied wood as plant growth regulators.