Can we exploit ornamental plants for phytoremediation purposes?

Several anthropogenic activities, such as agricultural practices, industrial activities and urbanisation, release pollutants that pose a significant threat to ecosystems and living organisms and compromise soil health and related ecosystem services. Among these pollutants, metals like arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), copper (Cu), and nickel (Ni) are widely present in the soil as toxic and long-term persistent elements. Currently, 2.8 million sites are potentially contaminated, with many more suspected to be at risk. Even the effects of climate change, associated with global warming and extreme events, can also alter the physical, chemical and biological properties of soils, with implications for the redistribution and transformation of metals. Phytoremediation offers a sustainable, in-situ, and eco-friendly solution by using plants to remove or immobilize contaminants. While the primary focus of this technique is soil reclamation using common (hyper)accumulator plants, aspects such as aesthetics and social acceptance are often overlooked. Ornamental plants with phytoremediation potential could be a promising alternative, as they not only clean metal-contaminated soils and reduce biomagnification risks but also deliver multiple ecosystem services.  The remediation capacity of these plants and their exploitation in polluted areas is poorly documented. For this reason, the aim of the study is to perform a systematic review on ornamental or hyperaccumulator plants with the ability to accumulate metals from soil.  A total of 83 articles were checked using selected keywords (e.g., phytoremediation, polluted soil, ornamental plants), and 130 taxa were analysed in terms of metal accumulated, physico-chemical strategies adopted by the plants, type of soil tested, invasiveness, geographical distribution, and aesthetic value. In general, plants are exposed to moderate to high metal concentrations in soils, often largely exceeding the law limits. Responses to metals are generally species-specific, with some exceptions concerning the accumulation of multiple metals by a single plant. For Cd uptake, Zinnia elegans Jacq. (129,18 mg/kg in root, 109,89 mg/kg in shoot) and Calendula officinalis L. (1084 mg/kg in root, 383 mg/kg in leaves) are utilized. In contrast, for Pb remediation, Dianthus barbatus L. (80–580 mg/kg in root, 414,3–843 mg/kg in shoot) and Rubus ulmifolius Schott. (248–1178 mg/kg in root, 25–49 mg/kg in leaves) show accumulation abilities for that metal. These species have been tested under various experimental conditions and soil concentrations, while their geographical distribution and ability to grow in different biomes make them suitable for different environmental conditions. Although these plants show potential for use in polluted areas, would be useful to carry out further studies that examine their ability to synergistically accumulate metals in multi-contaminated sites in different environmental contexts.