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Green sustainability is becoming more and more an issue in the management of urban greening. Accordingly, the use of native species of wild flora is increasing in urban greenspace design and restoration ecology because of their capacity of adaptation to adverse local environmental conditions and support long-term persistence of ecosystem recovery. Although the use of peat-free growing media is increasing in professional nursery, due to the environmental concerns around peat bogs exploitation, the use of materials suitable to replace peat in the growing medium is poorly investigated for the production of wild plants. In this work, we investigated the biomass production and the reproductive performances of eight native species (Agrostis stolonifera, Carex pendula, Dianthus carthusianorum, Iris pseudacorus, Leucanthemum vulgare, Lychnis flos-cuculi, Lythrum salicaria and Scabiosa graminifolia) and two ornamental species (Deschampsia caespitosa and Verbena bonariensis) in four different growing media (peat:pumice 70:30 v/v as a control; coconut coir dust:pumice 70:30v/v; coconut coir dust:green compost 55:45 v/v; coconut coir dust:green compost:stabilized wood fibre 40:30:30 v/v). Biomass accumulation and biometric indicators were assessed during blooming period, by measuring above-ground biomass, below-ground biomass, total biomass and, for a subset of species, number of flowering stems and number of flowers. Whilst plants grown in green compost and coconut coir dust media generally tended to have same biomass and comparable reproductive performances of plants grown in peat-based medium (with only one exception; i.e. Verbena bonariensis), plants grown in wood fibre media showed lower biomass accumulation, although not always (not all species) statistically significant. Green compost and coconut coir dust represented excellent substitutes of peat for the cultivation of native herbaceous plants in commercial nursery.

Restoration interventions of natural ecosystems, as well as degraded urban areas, require an accurate selection of plants, not only considering the genotype, but also the adopted growing techniques. Native species are to be preferred (often mandatory in restoration interventions and in some municipal regulations), being able to guarantee high eco-physiological responses, especially to post-transplanting plant stress. This feature is intrinsic of each species, but it is also highly influenced by agronomic techniques. The growing techniques usually adopted in the ornamental sector are aimed at obtaining high quality standard. Nevertheless, not always these methods lead to satisfactory post-transplanting performances, especially if transplanting cares, e.g., irrigation, are not available. Another critical issue in restoration interventions is the use of potted plants grown on peat-based substrates, which must be reduced/avoided in line with high sustainability requirements of this special sector as well as of waste policies. With the aim to evaluate post-transplanting responses of the Euro-Mediterranean native Viburnum lantana L., a one-year cultivation trial was conducted by testing different peat-free substrates, followed by transplanting in a degraded area of the "Parco Regionale Lombardo della Valle del Ticino". Tested growing media were: 1) peat:pumice 70:30 v v-1, as control treatment; 2) coconut coir dust:pumice 70:30 v v-1; 3) coconut coir dust:green compost 55:45 v v-1; 4) coconut coir dust:stabilized wood fibre 60:40 v v-1. Cuttings were planted in 4 L pots directly adding a controlled release fertilizer to the substrate, integrated with a top-dress controlled release one in the following early spring. Plant growth was monitored throughout the entire vegetative cycle by both non-destructive biometric measures (i.e., plant height, collar diameter) and eco-physiological parameters (i.e., gas exchange, efficiency of photosystem II and SPAD index). At the end of the cultivation cycle, some plants were sampled to assess root and shoot biomass productions and tissue nutrient contents, while 12 plants per treatment were transplanted in field in three randomized blocks. Irrigation was provided after the transplant and then plants were subjected to the environmental conditions (i.e., sunny, dry summer). At 100 days after transplanting both eco-physiological and destructive biometric parameters were collected (i.e., shoot biomass and leaf necrotic area). Plants grown in the tested peat-free substrates showed a faster response to transplanting stress respect to control plants, which showed higher phylloptosis and wider necrotic leaf area. This higher efficiency in recovery from transplanting stress was also highlighted by the ecophysiological measures.

One of the major challenges for nursery growers is replacing peat with more sustainable materials that may also represent a worthy strategy to recycle organic refuse. Among organic matrices, coconut coir dust, green compost, and stabilized wood fibre are considered promising alternative to peat because of their suitable physical-chemical characteristics. These matrices were used to prepare substrate mixtures designed to achieve physical characteristics similar to those of the standard peat-based substrates usually adopted by growers (peat:pumice, 70:30 v v−1). An experiment was carried out in open field with Leucanthemum vulgare Lam., a plant species that could be used for ecological restoration, by using both the native and the ornamental variety of the same species (L. vulgare cv. ‘Filigran’), the latter as test plants. Six different growing media were tested: (i) peat:pumice 70:30 v v−1 (PP), used as commercial control; (ii) coconut coir dust:pumice, 70:30 v v−1 (CP); (iii) coconut coir dust:green compost 55:45 v v−1 (CGC); (iv) coconut coir dust:stabilized wood fibre 60:40 v v−1 (CW); v) green compost:stabilized wood fibre 30:70 v v−1 (GCW) and, (vi) coconut coir dust:green compost:stabilized wood fibre 40:30:30 v v−1 (CGCW). Plant biomass, biometric parameters, plant and matrix/substrate mineral content, and mineral composition of water drained out from pots were measured as main performance indicators of plants and growing media. All the tested peat-free substrates, with the exception of GCW, adequately supported plant growth and quality. Moreover, CP and CGCW improved some of the investigated biomass and biometric parameters compared with the control treatment. Substrates containing green compost were found to improve plant nutrition, because of the high availability of mineral elements in the raw material.

Studies on the use of peat-free growing media to grow potted ornamental plants are nowadays increasing, due to environmental concerns around the exploitation of peat, but these kind of studies on materials suitable to replace peat in the medium of cultivation are lacking with respect to cutting production. In this work, we investigated rhizogenesis on cuttings of four ornamental species (Viburnum rhytidophyllum L., Pyracantha koidzumii x P. coccinea 'Mohave', Prunus laurocerasus L., Euonymus japonicus Thunb., Ligustrum sinense Lour.) planted on the following growing media: 1) peat:pumice 70:30 v v-1 (control); 2) coconut coir dust:pumice 70:30 v v-1; 3) coconut coir dust:green compost 55:45 v v-1; 4) coconut coir dust:green compost:stabilized wood fibre 40:30:30 v v-1; 5) coconut coir dust 100 v v-1; 6) green compost 100 v v-1; 7) stabilized wood fibre 100 v v-1. 12 cm-leafed-cuttings (with 4-6 leaves) were prepared and treated with 4000 ppm indole-3-butyric acid (IBA), 4000 ppm 1-naphthaleneacetic acid (NAA), 4000 ppm IBA+NAA or without hormones. After 120 days, rooting and shooting were evaluated taking into account dry weight of roots, the root length and the root area (cm2). Cuttings grown on substrates with green compost and coconut coir dust generally tended to have same performances of cuttings grown on peat-based media while the cuttings grown on stabilized wood fibre media showed lower rooting grown. In general, data showed that green compost and coconut coir dust could represent excellent substitutes and alternatives to peat for the cultivation of cuttings in commercial nursery providing innovation elements regarding the total elimination of peat during the propagation phase of plants.