New tools to support sustainable urban green design – the potential of herbaceous perennials in new demolition waste-based substrate

New solutions for more resilient and sustainable cities are needed. Urbanization has caused lack of space for implementing green areas, and increased many environmental problems in cities, related to air, water, soil and waste management. This project was developed in the Metropolitan area of Turin (northern Italy) with the aim of evaluating construction waste as a planting substrate for a new public park. To evaluate their response in terms of vegetative development, physiological state and weed development plants will be grown for three years from spring 2023. The present paper discusses preliminary results from the first year of research. Three herbaceous perennials, Achillea millefolium L. ‘Summer Pastels’, Potentilla nuemanniana L. and Hemerocallis hybrida L. ‘Stella De Oro’ will be evaluated in an urban park in the metropolitan city of Turin (Italy), from 2023 for three years to evaluate their response in four plots with different substrates. The amount of soil (S), compost (C), recycled drywall (D) and demolition waste (DW) used were: control (100% S), T1 (40% S, 20% C, 5% D, 35% DW), T2 (30% S, 20% C, 15% D, 35% DW) and T3 (20% S, 20% C, 10% D, 50% DW). Each plot was divided into nine parts, with three replications for each species, (size 1.5×2 m). For each species, we measured biometric parameters such as growth index, stomatal conductance for evaluation of physiological traits, fresh weed biomass harvested, and the chemical and biological fertility of substrates. The preliminary results of the first growing period indicate that all the species studied grow better in T2 (35% DW + 15% D). Regarding the weed incidence, the substrate composed of a total of 60% of DW and D (T3) presented three to four times lower fresh weed biomass than others. Among the tested species, A. millefolium ‘Summer Pastels’ was the most vigorous and suppressed weed emergence. Regarding soil fertility, in general T1, T2, and T3 contained more nutrients than the control plot. This experiment will provide new tools useful for sustainable design, planting and recycling to be suggested.