Antoine Yaccarini, a PQ spokesman, says Garon died in hospital in Levis.
He says the family had not released the cause of death.
Garon had been active in the sovereignty movement before the founding of the PQ in 1968.
After a first defeat as a PQ candidate in 1973, Garon was elected to the legislature three years later in Levis, a city he had previously represented as mayor.
He served as agriculture minister for nine years, until the PQ was defeated in 1985.
One of his proudest accomplishments was getting legislation passed that protected Quebec farmland.
He was beaten by Pierre Marc Johnson when he ran for the PQ leadership in 1985 and was named education minister by Jacques Parizeau in 1994 after the PQ returned to power.
Garon, who was trained as a lawyer and an economist, quit provincial politics in 1998 and was elected mayor of Levis the same year. He held that job until he was defeated in 2005.
Francois Gendron, a Pequiste who is the longest-serving current member of the legislature, described Garon Wednesday as someone of ferocious determination.
"No one can doubt the sincerity and the authenticity of this man," said Gendron, pointing not only to Garon's character but his political accomplishments.
"He put Quebec agriculture on the map," Gendron said. "He brought it from the margins where it was."