The main West Iranian languages, i.e. Old Persian, Parthian, Middle Persian, New Persian and – in some respects – Avestan, may be studied in a uniquely continuous development stretching over close to 3 000 years. These languages are not only the result of their genetic inter-relations but also of their cultural, religious and political history. They may be labelled ‘high languages’ (‘Hochsprachen’), in the sense that they are cultured and standardized and used for a great number of purposes by people of various linguistic backgrounds. This article presents an over-view of their development seen from a specific perspective. The traditional Iranian walled-in garden, the pairi-da?za- of the Avesta, is used as a metaphor for a high language in contrast to the free vegetation of spontaneous human speech in social interaction. The latter is here called ‘dialect’, a concept that includes both ‘geolect’ and ‘sociolect’. These high language ‘gardens’ are thus viewed as a kind of cultural artefacts. Among other things, this has implications for views on the dichotomy literacy/orality, showing that writing is not language and that ‘orality’ belongs both to ‘high language’ and ‘dialect’. It is furthermore argued that literacy and orality were present in complementary distribution throughout the whole known history of the Iranian cultural sphere.