"I knew last year that the brain tumour was terminal, and thus I knew he would leave and I would be alone," Berge added.
Berge will also be cremated and his ashes scattered next to his partner's when he dies, he revealed.
Guests enjoyed a lunch in the shaded canopy of exotic trees after the ceremony.
"Pierre Berge's idea to scatter Yves Saint Laurent's ashes in this country, which he loved above all, in this gorgeous and magical house, is a beautiful idea, and somehow it is a fitting way to be reconciled with his death," Lang said.
The Majorelle garden is home to flora from five continents, with 350 species, including a superb collection of cactuses, plants, palms, bamboos and ferns from Latin America.
"I will always treasure one dinner he gave," said TV anchorwoman Chazal. "It was very intimate. He was on top form. At the same time it was a little sad, because he was already a little bit aged, but you could still see the twinkle in his eye, because he had so much humour and compassion."