In this paper the sound absorption properties of two types of plants for indoor applications are analyzed. The aim of this research is to investigate the feasibility of using the selected plants (Nephrolepis Exaltata, Boston fern and Helxine soleirolii, baby tears) in green walls for indoor applications, in order to improve the acoustic quality of interior environments. These two types of plants are able to live in green wall systems thanks to their capability to live in indoor climate conditions. Indeed they are able to branch in horizontal condition and furthermore to live without direct sunlight illumination. The plane wave absorption coefficient of ten specimens of fern and three of baby tears were measured in presence and in absence of a substrate. The chosen substrate is made of coconut and perlite soil, commonly used in hydroponics; its composition allows to obtain high porosity values. The sound absorption coefficient spectra was measured in the frequency range of 50 – 1600 Hz using a vertically mounted impedance tube with a diameter of 100 mm; measurements were carried out in accordance with ISO 10534-2 method. After measuring the normal incidence sound absorption coefficient with impedance tube, the equivalent fluid model for sound propagation by Miki was used to deduce non-acoustical properties of the samples. The inverted Miki’s model allowed to find the theoretical tortuosity (α_∞) and the flow resistivity (σ). These non-acoustic properties were then related to morphological characteristics of specimens. It is shown that the leaf area density is closely related to flow resistivity, at least for Boston fern; the data allowed to identify a semi-empirical relation between them. Finally an application of the developed green system for the acoustic treatment of a real case study is reported.