Understanding the root system architecture (RSA) is necessary for elucidation of plant growth patterns in response to environmental stimuli and hormonal signals. Ethylene, a gaseous phytohormone, modulates root developmental plasticity, including primary root elongation, lateral root formation, and root hair growth. We present a protocol for mapping ethylene-specific RSA traits in Arabidopsis thaliana using a hydroponic growth system. Arabidopsis seedlings grow on a polypropylene mesh supported by polycarbonate wedges in a magenta box-based setup. We treat seedlings with ethylene or its precursor, then spread root system on agar plates with an art brush. High-resolution images are recorded and analyzed with free ImageJ software. This protocol allows detailed RSA analysis under controlled ethylene treatments and can be adapted for other plant species.