Treated sediment as substrate component of three containerized ornamental species: effects on marketable and qualitative traits

From Firenze University Press Journal: Advances in Horticultural Science

M. Castellani, Flora Toscana

D. Bonetti, Council for Agricultural Research and Economics, Research Centre for Vegetables and Ornamental Crops

M. Antonetti, Council for Agricultural Research and Economics, Research Centre for Vegetables and Ornamental Crops

D. Prisa, Council for Agricultural Research and Economics, Research Centre for Vegetables and Ornamental Crops

G. Burchi, Council for Agricultural Research and Economics, Research Centre for Vegetables and Ornamental Crops

S. Nin, Council for Agricultural Research and Economics, Research Centre for Vegetables and Ornamental Crops

The ornamental plant industry in Tuscany is a strategic sector, repre­senting approx. 5% of the entire national agricultural production, which derives for about 75% from potted plants and nurseries (trees and shrubs) and for the remainder from fresh cut flowers and foliages (Martorana, 2021). This segment produces a giant assortment of ornamental and flow­er species in about 6,500 hectares of land, concentrated in the provinces of Pistoia and Lucca. With over 3,300 nursery enterprises, 2,060 of which are ornamental producers and 1,900 flower growers, this sector has a large impact on employment and induced economy, as well as a strong export vocation (Pagliantini, 2020). The power of this sector lies in the variety of the assortment offered for sale and therefore nursery industries are constantly looking for new species and cultivars. Another important factor for the expansion of this sector is the adaptation of new production technologies to the concept of sustainable develop­ment.

Great deal of the ornamental and flowering plant production is carried out in containers and depends almost entirely on the quality of soilless media derived from both organic and inorganic con­stituents. Indeed, since successful container cultures depend on producing a stable finished plant, different components in the growing substrate can pose signifi­cant problems if they affect growth rate, nutrition or plant shape and aesthetics (Salachna, 2022). Its unique physical properties and large availabili­ty have led peat to be the dominant organic con­stituent of growing media in many parts of the world in recent decades. Nevertheless, other organic mate­rials have been recently attracting more attention as a partial substitute for sphagnum peat in a container growing medium (Fascella, 2015; Barrett et al., 2016). Among these is coir, regarded as a rapidly renewable resource, as it is a by­product of coconut harvest.

Moreover, especially in Europe, innovative approach­es have involved an increasing use of locally available organic materials such as bark (wood fibre) and transformation of composted wastes as next­genera­tion constituents of growing media. Perlite or vermi­culite components are often used to improve drainage and aeration (Gruda, 2019). Recent studies have focused on the possibility of reusing sediments in agriculture by combining them with standard growing media or biochar amendment (Renella, 2021). This practice could be best success­fully applied to ornamental species grown in contain­ers, where health risk due to the presence of toxic residues are minimized. Thus, in this study we inves­tigated the effect of a treated sediment as a sub­strate component on the quality and marketability of three widespread containerized ornamental species: cherry laurel, calla lily and protea. Prunus laurocerasus ‘Novìta’, commonly known as cherry laurel, an evergreen ornamental with a very fast growing and plant development, is one of the most commercially important outdoor ornamental species for the Italian nursery. The cultivar ‘Novìta’, selected in Holland, has now become widely estab­lished and has replaced the previous cultivar ‘Caucasica’, compared to which it has longer, thicker, and shinier leaves, and above all, is more resistant to diseases and water stress (Ilnitsky et al., 2019). Nowadays, container­grown cherry laurels, as all out­door nursery plants, can be sold at any time of year with two major peaks in spring and autumn.

Its com­mercial value is a function of the size of the plant, first of all its height. Calla lily (Zantedeschia aethiopica) is a very popu­lar flower of great world economic importance, grown as cut flower, potted or garden plant. This species flowers from late summer into spring in frost free areas and prefers partially illuminated environ­ments (De Hertogh, 1996). Calla cultivation is spread from central to southern Italy, where it is performed indoor under greenhouse conditions to protect the crop from October to the end of April (Janowska and Andrzejak, 2022). On the market, cut flowers are classified into grades based on the size of the stem and the flower (spathe). Furthermore, the sale price varies throughout the year, reaching the highest val­ues in the winter period and the lowest values in the month of April, when the quantity of flowers offered on the market is highest. The protea used in this experiment was Protea cynaroides dwarf ‘Little Prince’, a patented variety, bred for flowerpot production at the National Research Council of South Africa.

This cultivar differs from the well­known protea King, national flower of South Africa, for its compact habit, which makes it suitable for expanding the potted plant floral market. Protea is an unusual plant for Europe, where it is con­sidered a niche product much appreciated by fans of exotic plants. Commercial growing of proteas for the cut flower market is increasing also in other European regions with mild winter, especially Portugal and Canary Islands (Lewis and Matthews, 2002; Claassens, 2017). At the marketing stage, pro­tea potted plants are graded and priced according to the number of flowers. These species were used as model plants of the ornamental plant sector (evergreen shrubs, flower­pot, cut flower) to assess the commercial potential of sediment­ based growing media combined with sphagnum peat, coir and wood fibre on the existing floriculture market.

DOI: https://doi.org/10.36253/ahsc-13998

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