The Greeks and the Arabs were not familiar with cotton until the Wars of Alexander the Great, as his contemporary Megasthenes told Seleucus I Nicator of "there being trees on which wool grows" in "Indica". This may be a reference to "tree cotton", Gossypium arboreum, which is a native of the Indian subcontinent.
According to the Columbia Encyclopedia:
Cotton has been spun, woven, and dyed since prehistoric times. It clothed the people of ancient India, Egypt, and China. Hundreds of years before the Christian era, cotton textiles were woven in India with matchless skill, and their use spread to the Mediterranean countries.
In Iran, the history of cotton dates back to the Achaemenid era ; however, there are few sources about the planting of cotton in pre-Islamic Iran. The planting of cotton was common in Merv, Ray and Pars of Iran. In Persian poets' poems, especially Ferdowsi's Shahname, there are references to cotton Marco Polo refers to the major products of Persia, including cotton. John Chardin, a French traveler of the 17th century who visited Safavid Persia, spoke approvingly of the vast cotton farms of Persia.