Cultivation effect of Caryopteris clandonensis and Euonymus fortunei in roof greening substrates

Caryopteris clandonensis and Euonymus fortunei have the following characteristics: drought resistance, barren resistance, pruning resistance, easy survival, extensive management, and high ornamental value during their flowering period. They can break up the monotonous landscapes in roof greening projects that otherwise use plants which are prone to diseases and insect pests, easy to damage, and have other deficiencies. However, there are few studies and reports about the cultivation of these two plants in light roof greening substrates. Two treatments were designed for each plant, resulting in the following four treatments: substrate 1 + Caryopteris clandonensis, substrate 2 + Caryopteris clandonensis, substrate 1 + Euonymus fortunei, and substrate 2 + Euonymus fortunei. Substrate 1 was m _perlite ꞉ m _{fly ash} = 100 ꞉ 15, substrate 2 was m _perlite ꞉ m _{fly ash} = 100 ꞉ 20. In this paper, the cultivation effect of light roof greening substrates made up of perlite and fly ash on the two plants after one year of growth was studied. Results showed that in substrate 2, Caryopteris clandonensis and Euonymus fortunei plant height, fresh weight on the ground, ground dry weight, root dry weight, root length, root area, root diameter, and root volume were significantly higher than that in substrate 1 (P < 0.05). However, there was no significant difference in Caryopteris clandonensis and Euonymus fortunei chlorophyll content or root cap ratio between the two substrates. Pearson correlation analysis showed that the pH, total nitrogen, and total phosphorus of the substrates were significantly related to plant growth status (P < 0.01), followed by field water capacity, capillary porosity, and EC (electrical conductivity) (P < 0.05). The comprehensive evaluation ranked the effect in the following order: substrate 2 + Caryopteris clandonensis, substrate 1 + Caryopteris clandonensis, substrate 2 + Euonymus fortunei, and substrate 1 + Euonymus fortunei. In conclusion, substrate 2 had a better effect on the cultivation of Caryopteris clandonensis and Euonymus fortunei.