Performance of Sedum native species on an estensive green-roof system in Bologna surroundings, Italy: flowering and coverage pattern in relation to propagation

none2The genus Sedum includes the most popular species of perennials for extensive green roof systems, with thin substrate and not irrigated conditions in dry Mediterranean areas, too, as the result of drought and wind tolerance, ability to withstand temperature extremes, rapid establishment, long life and fast self-propagation. The horticultural available sedums are more than 50, including cultivars and species, but many regional forms can be identified, morpho-physiologically different and well adapted to specific pedo-climatic conditions. Five Italy native Sedum types (S. album, ‘green’ and ‘grey’ forms of S. reflexum, S. sexangulare, S. hyspanicum var. pallidum) from the Appennino Tosco-Emiliano have been grown in modules for extensive green roof, with a 9 cm substrate, including 8-12 mm and 3-5 mm volcanic tuff in the bottom and in the superficial layer, respectively, and gravel on top. The percentage of coverage, plant height, flowering period and length were valuated over one year, from October 2006, in relation to type (tip or stem) and weight (g/m2) of cuttings at planting. At flowering time, after 7.5 months from planting, the S. reflexum ‘green’ type resulted taller and earlier (7 ± 2days) than ‘grey’ one and exibited a coverage around 10% higher, from digital image analysis (48.7-38.4 % coverage respectively, starting from 100 cuttings, equivalent to 200 g/m2/ ). The cutting number seems to influence coverage more than initial cutting weight. Plant area of S. album, S. sexangulare and S. reflexum ‘grey’ was alike (10.3-10.7 and 13.6 cm2/plant) with a higher establishment capacity of tip than stem cuttings. Flowering period ranged from the15th May to the end of June. All types tested survived during winter and resulted suitable for the use on non irrigated extensive systems, except for S. hyspanicum var. pallidum because of its growth as an annual and leaf lack during summer.noneGiorgioni M.E.; Neretti U.Giorgioni M.E.; Neretti U