The victims - school teacher and his 12-year-old son - were examine the plants when one of them stepped on the landmine resulting in the explosion near a police check post in Mardan district of Khyber Pakthunkhwa, police said.
Police rushed to the spot and initiated search operation in the area. The bodies were shifted to Mardan medical complex for postmortem.
Meanwhile, Peshawar police today arrested two suspected terrorists during a raid on a house here and seized huge cache of explosives.
The security officials also seized explosive material weighing 320 kg from the hideout of the miscreants.
A large number of connectors, remote controls and suicide jackets were also recovered from the house.
The neighbours said that the two had a white Suzuki van which they used for illegal activities.