Cultivation of the herb Origanum dictamnus in an urban extensive green roof under different substrate types and irrigation frequencies

The suitability of Origanum dictamnus, a xerophytic herb endemic of Crete, with aromatic, medical and ornamental value, for use in extensive green roofs in semi-arid Mediterranean areas, under limited irrigation, was investigated.
Additionally, two substrate types were tested aiming to reduce green roof construction weight.
Rooted cuttings were planted in July 2011, on 10 cm depth substrate with a green roof infrastructure (substrate moisture retention and protection of the insulation mat, drainage element and filter sheet), on a roof at the Agricultural University of Athens and were cultivated for 26-months.
The two types of substrate used were one with soil, i.e. grape marc compost: perlite: pumice: soil (3:3:2:2, v/v) and a lighter one without soil, i.e., grape marc compost: perlite: pumice (3:3:4, v/v). Two irrigation frequencies were applied (to substrate saturation) during the dry periods, i.e., every 5 days (normal) and 7 days (sparse) in 2011 and 2012 and every 4 days (normal) and 6 days (sparse) in 2013, when substrate moisture was 17-20% and 5-11% for normal and sparse, respectively.
Normal irrigation and soil containing substrate promoted the final diameter of the plants, while normal irrigation promoted the shoot number as well.
Thus, the combination of soil-based substrate and normal irrigation induced the largest plant growth; however, the plants grew quite satisfactorily in the soilless substrate combined with sparse irrigation.
Although sparse irrigation resulted in increased stomatal resistance one day before irrigation, indicating water deficiency, no permanent photoinhibition was developed in plants under sparse irrigation.
So, for water conservation reasons and lighter construction weight, soilless substrate with sparse irrigation is recommended for the cultivation of O. dictamnus in urban green roofs.

IV International Symposium on Horticulture in Europe – SHE2021

L. Tassoula, M. Papafotiou, G. Liakopoulos

Cretan dittany, grape marc compost, Mediterranean aromatic plant, pumice, water stress

https://doi.org/10.17660/ActaHortic.2021.1327.65