Which cast phull belongs to?

Phull/Phul/Phool is one of the most uncommon surnames in punjab....

people of this surname are punjabi khatris .The Khatris are a north Indian community that originated in the Potwar Plateau of Punjab.

There might even be a few jatt or tarkhan tribes which share this surname.

They are the descendents of Phul Singh Sandhu a 17th century ruler in Punjab.