We all know that Morris is an objector to chemical dyes, he preferred to use natural plant dyes. At that time, the knowledge of using natural dyes was disappearing quickly , and he made his efforts to revive it.

He studied Indian painted textiles, and the colors and patterns inspired his early work of cotton crafts. Actually, before 18th century, India always have more advanced textile producing technology than Europe.

The emperors of India in Mughal dynasty loved plants quite much, and the patterns of flowers was stylish at that time and a lot of artists painted them.

Reference:

http://www.vam.ac.uk/content/articles/i/indian-textiles-introduction/