She attended a French primary school, then, for her senior years, Fahan School, both in Hobart. Di studied Physiotherapy at Melbourne University and completed half of a Bachelor of Arts degree there. She met Kevin John Cullen when he was undertaking a medical degree at the same university. They married in Hobart in 1946 and moved to Busselton in 1948. Kevin worked in a general practice in Busselton. They had six children.
They started growing grapes in 1956 and, more seriously in 1966, embarked on an experimental planting of cabernet and Riesling cuttings from the Swan Research Station after Dr John Gladstones wrote his thesis on the region being among the three best in the world for producing wine. In 1971, 17 acres of wine grapes were planted at the present location, and this has been increased over the years to around 50 acres. Di became the wine maker while Kevin continued his medical practice in Busselton.
The winery on the site was built in 1974. Through trial and error, reading and travelling to observe other wineries in Australia and around the world, the Cullens have developed a winery that has recognition throughout the world for quality wines. Di Cullen emphasizes that they strive for quality rather than quantity. Since Di Cullen’s untimely death, their daughter, Vanya, has taken over as the wine maker.
The Cullen’s do not irrigate their vines and their vineyard is as environmentally friendly as possible using mulch for weed control and very little spraying. Di and Kevin were aware that a region name was very important to the marketing of local wines and the Margaret River Wine Region developed.