Growing of the Cretan Therapeutic Herb Origanum Dictamnus in The Urban Fabric: The Effect of Substrate and Cultivation Site on Plant Growth and Potential Toxic Element Accumulation

Urban Farm DB summary

Origanum dictamnus, a perennial herb endemic to Crete, Greece, was grown at two cultivation sites in Athens — an extensive green roof and ground level next to a moderate-traffic road — in two substrate types at 10 cm depth, to examine growth along with nutrient content (N, P, K, Na) and heavy metal accumulation (Cu, Pb, Ni, Mn, Zn, Fe) in its tissues. Plant growth was favored by the soil substrate but was also satisfactory in the soilless substrate. Cultivation site affected heavy metal accumulation, with higher concentrations found in leaves and flowers at street level, though no differences appeared in roots. Washing reduced heavy metal concentrations only in leaves grown at street level. Substrate type significantly affected manganese concentration in all tissues and iron concentration in roots, with the highest values in the soil substrate. The species could be cultivated on sustainable green roofs, preferably on a soilless substrate to reduce structural weight, but careful selection of the cultivation site was identified as necessary to minimize contamination with environmental pollutants when human consumption is intended.