Germination ecology of wild living walls for sustainable vertical garden in urban environment

- Urban greening needs ecological sustainability.
- Wild germplasm from naturalized living walls demonstrate potential for vertical gardens.
- Standard physical, chemical or physiological treatments are sufficient to overcome seed dormancy.
- Nursery protocol can be developed for wild xerophyte propagation which should increase plant availability.

Germination characteristics of 10 xerophytic species, widespread in the Mediterranean were studied. A variety of seed treatments were explored to overcome the seed dormancy, including scarification and stratification. Only in Convolvulus cantabrica dormancy was shown to be physical, since it could be removed by seed coat scarification. Several species showed light-dependent germination, possibly related to the fact that in their micro-environment of incubation they are exposed to minimum seed burial. Emergence tests in peat-perlite substrate were carried out in order to verify the optimal burial conditions for seed propagation. This inhibition was found to be inversely related to the low unit weight of seed. Species with minute seeds, such as Erigeron karviskianus and Phagnalon rupestris, had the best performance of germination without burial, while the larger ones such as C.cantabrica and Centranthus ruber, had the best performance at 6 and 4 mm of sowing, respectively.