## 4 Results
### Plant Selection: Key Results
#### 4.3.2 Plant Selection and Green Roof Development: In-Field Testing within the Prototype  
For the plant selection and design of the \"PV Rooftop Garden\", in general the same requirements used for any type of extensive or intensive green roof regarding load weight, waterproofing, drainage, growing media, and suitable plants should be fulfilled [19; 20; 21; 46; 47]. As the \"PV Pergola\" is not connected to the building, the weight of the substrate will provide the needed weight to hold the construction down against wind suction. In the case of a retrofit, the possible and needed height of the substrate has to be calculated based on the actual structural requirements of the building and depending on the specific wind and snow loads and the additional weight of the construction. In the testing facility of the BOKU (on the third floor of a university building in Vienna) (see Figure 4, the green roof layer had to be 20 cm (with a maximum substrate weight of 1400-1500 kg/m\({}^{3}\)) to fulfill the minimum structural requirements. Additional irrigation is necessary if not enough rainwater for sufficient watering of the plants can be stored in the substrate. This also has to be taken into account in the dimensioning of the substrate. In the testing facility at the BOKU, three different light zones that were to varying degrees influenced by the shading of the PV panels were identified with hemispheric photography:  
* Zone 1: mostly unshaded areas with little influence from the PVs (260-360 MJ/(m\({}^{2}\)year));
* Zone 2: semishaded areas (160-260 MJ/(m\({}^{2}\)year)); and
* Zone 3: mostly shaded areas with strong influence from the PVs (under 160 MJ/(m\({}^{2}\)year)). Within these areas, different plant species, annuals, herbaceous perennials, grasses, and climbing plants were surveyed over a period of three years. On the basis of their vitality, growth, and flowering success after the three-year monitoring period, suitable plants for the different zones could be identified. Lawn: This was a mixture of species in a dry lawn area consisting of 80% grass (_Cynodon dactyllon_, different species of _Festuca_, _Lolium perenne_, and _Poa compressa_), 8% leguminoses (_Anthyllis vulneraria_, _Lotus corniculatus_, _Medicago lupulina_, and _Trifolium repens_), and 10% herbs (_Achillea millefolium_, _Bellis perennis_, _Dianthus carthusianorum_, _Galium verun_, _Hieracium pilosella_, _Petroh Hagia saxifraga_, _Plantago media_, _Potentilla tabernaemontani_, _Salvia nemorosa_, and _Thymus pulgeioides_) seeded in a semishaded to sunny zone. The grasses grew fast and successfully, while the herbs and leguminoses only grew in the mostly sunny border zones. Edible plant species/plants for urban gardening: _Fragaria vesca_ and _Allium schoenophrasum_ grew in all zones, but there was less flowering in zones 2 and 3, which had more shade. _Capsicum annuum_, _Foeniculum vulgare_, and _Ocimum kiliman_ x _basilicum_ had a very good vitality and growth rate in all light zones. In addition, _Mentha_ x _piperita_, _Eruca sativa_, and _Origanum vulgare_ successfully grew in all light zones and spread so dominantly that they had to be reduced after the second year. _Solanum lycopersicum_ grew in both the mostly unshaded and semishaded zones. _Raphanus sativus_ var. _sativis_, _Brassica oleracea_ convar. _capitate_, _Beta vulgaris_ subsp. _Vulgaris_, and _Lactuca sativa_ var. _capitata_ had no satisfying growth in zones 2 and 3. _Phaseolus vulgaris_ var. _vulgaris_ had no satisfying growth rate in any zone. A summary of the suitability of edible plant species for the different light zones is shown in Table 2.  
Annual and biannual plant species: _Antirrhinum majus_ self-spread wildly over all light zones, _Verbascum nigrum_ grew in the sunny and semishaded zones, and _Calendula officinalis_ disappeared after the first year. _Echium vulgaris_ and _Silene vulgaris_ self-developed during the third year in the semishaded and sunny zones.