Sam Popham first came to Sri Lanka, then Ceylon, with the Royal Navy. He later became a tea planter in the 1940s. His abiding love for trees encouraged him to work on the Smithsonian Ceylon Flora Project. While engaged in this work he acquired the property at Dambulla and started to plant the land with Mango trees. This however did not prosper and he then decided to replace the scrub jungle with as many species of Sri Lankan native trees as he could find. So started the Arboretum. He lived on the land for 38 years firstly in a very basic cottage which is on the left of the entrance to the property.
He later moved into the cottage, designed for him by Geoffrey Bawa and which today serves as the Visitor Centre. He lived in this cottage for 28 years with the trees as his constant companions. His adopted family Setunga and his wife and two daughters lived close by and were constantly in and out of the property. Sam lived at the Arboretum until 2001, after which he went back to England to retire there.