I believe this is Capparis spinosa, which I photographed growing out of a rock wall in Greece, however it could be C. orientalis. Other close relatives include C. aegyptia and C. sicula, all of which grow in similar environs and often near one another. The caper bush is present in almost all Mediterranean countries. Here’s a photo of the caper flower taken last year. And a photo of Capparis cartilaginea, from Oman.
The caper bush is a rupicolous species, meaning it thrives among and/or inhabits rocks. It is widespread on rocky areas and is grown on a wide range of different soil associations, including alfisols, regosols and lithosols. C. spinosa can tolerate both silty clay and sandy, rocky or gravelly surface soils, with less than 1% organic matter. It grows on bare rocks, crevices, cracks and sand dunes in Pakistan, in dry calcareous escarpments of the Adriatic region, in dry coastal ecosystems of Egypt, Libya and Tunisia, in transitional zones between the littoral salt marsh and the coastal deserts of the Asian Red Sea coast, in the rocky arid bottoms of the Jordan valley, in calcareous sandstone cliffs at Ramat Aviv, Israel, and in central west and northwest coastal dunes of Australia. It grows spontaneously in wall joints of antique Roman fortresses, on the Wailing Wall, and on the ramparts of the castle of Santa Bárbara (Alicante, Spain). Moreover, this bush happens to grow in the foothills of the southern Alps (Verona, Italy) and is a common species on city walls in Tuscany (Italy) and on bastions of Mdina and Valletta (Malta). Clinging caper plants are dominant on the medieval limestone-made ramparts of Alcudia and the bastions of Palma (Majorca, Spain).
Capers can be propagated easily from seeds sewn in a well drained soil. Allow 2-4 weeks until germination.
In Greece caper leaves are eaten in addition to the pickled buds. The leaves can be similarly pickled or boiled and preserved in jars with brine. Caper leaves are excellent in salads and fish dishes. Dried caper leaves are also used as a substitute for rennet in the manufacturing of high quality cheese.