Contents lists available at ScienceDirect Urban Forestry & Urban Greening journal homepage: www.elsevier.com/locate/ufug Improving the performance of felt-based living wall systems in terms of irrigation management Maria P. Kaltsidi a , Rafael Fernández-Cañero b , Antonio Franco-Salas a , Luis Pérez-Urrestarazu a, * a Urban Greening and Biosystems Engineering Research Group, Area of Agro-Forestry Engineering, Universidad de Sevilla, ETSIA Ctra. Utrera km.1, 41013, Seville, Spain b Urban Greening and Biosystems Engineering Research Group. Department of Agro-Forestry Sciences, Universidad de Sevilla, ETSIA Ctra. Utrera km.1, 41013, Seville, Spain ARTICLE INFO Handling editor: Ian Mell Keywords: Fytotextile Green walls Vertical greening systems Water management Water retention capacity ABSTRACT Vertical greening systems are becoming a new reality worldwide in urban areas in order to increase and enhance green spaces. Commercially there are many systems employing various materials which aim to enable an ade- quate development of the vegetal cover, ensuring long-term successful performance. Irrigation represents one of the main key factors, but there is a knowledge gap involving the performance of commercial systems in terms of water management. Felt-based systems present more difficulties due to the smaller water retention capacity, which is an important drawback, especially in warm climates. This work aims to improve an existing commercial system (Fytotextile) in order to optimise water retention and vegetation performance in harsh climate condi- tions. Therefore, three evolutions of the Fytotextile system were tested in terms of water retention capacity, drainage and vegetation performance. Fytotextiles 3 and 4 vastly improved the initial water retention capacity of the commercial system (2.9 and 5.8 times that of Fytotextile 1, respectively) but the former exhibited a lower volume of water drained and a slightly better behaviour of the plants. 1. Introduction Nowadays, the use of vertical greening systems is spreading worldwide under different outdoor climates and microclimate condi- tions as well as indoor environments (Ghazalli et al., 2019; Medl et al., 2017; Pérez-Urrestarazu et al., 2015). However, despite the multiple known benefits and ecosystem services provided by them (Collins et al., 2017; Ghazalli et al., 2019; Larcher et al., 2018; Medl et al., 2017; Pérez et al., 2016), these green technologies are often subjected to criticism, specially regarding their maintenance and environmental sustain- ability. Precisely, the excessive water use becomes one of the main concerns (Manso and Castro-gomes, 2015; Riley, 2017). Regardless of the green wall technology used, watering the vege- tation is compulsory, mostly by means of integrated irrigation systems (Medl et al., 2018). This is particularly important in the cases of in- stallation in warm climates where a proper irrigation schedule can be critical for the performance or even the survival of the vegetation. However, water management related to living walls has not been broadly studied, so there is a knowledge gap in this matter (Pérez- Urrestarazu et al., 2015). There are different living wall systems in the market (Manso and Castro-gomes, 2015; Medl et al., 2017; Pérez-Urrestarazu et al., 2015). Some of them are based on boxes or containers, which limit the roots development (e.g., root-bound plants) as they are confined (Weinmaster, 2009) and, frequently, they do not allow enough gas exchange, leading to an undesirable reduction of their growth rate (Pallardy, 2008). As an alternative, the ‘felt’ (also referred to as ‘cloth’) systems are usually formed by at least two textile-like layers (a geo- textile is the material most employed), in between which the plants are placed, bare rooted or in an inert substrate. The layers serve as a sup- port to the plant and at the same time they act as a media to provide water and nutrients to the roots. This kind of systems solves the pro- blem of excessive size (thickness) and weight of those based on con- tainers. The major drawbacks of this system are its low water retention capacity which forces having frequent irrigation events to provide the water required by the vegetation (Pérez-Urrestarazu et al., 2014) and less water distribution uniformity (Pérez-Urrestarazu et al., 2014; Segovia-Cardozo et al., 2019). This is particularly problematic in warm climates and usually results in excessive water use (especially when the system is not recirculated). Also, as felt-based living walls can be con- sidered a hydroponic system (since usually the plant’s organic medium of development is changed for an inorganic one) (Manso and Castro- gomes, 2015), additional nutrients must be incorporated (and part of them lost with the drainage water). https://doi.org/10.1016/j.ufug.2020.126782 Received 28 December 2019; Received in revised form 2 June 2020; Accepted 30 June 2020 ⁎ Corresponding author. E-mail addresses: markal1@alum.us.es (M.P. Kaltsidi), rafafc@us.es (R. Fernández-Cañero), afranco@us.es (A. Franco-Salas), lperez@us.es (L. Pérez-Urrestarazu). Urban Forestry & Urban Greening 54 (2020) 126782 Available online 06 July 2020 1618-8667/ © 2020 Elsevier GmbH. All rights reserved. T