Farmer Murders & Plants Victims In Garden

Hi, I think this movie was in the 70's, where a girl gets hurt & recovers in an old farmer's house...he is played by a movie star of yesteryear and he is tall & thin. In the film, he runs the farm with his very fat sister. The girl marries him, unaware that bro & sis murder people and plant them in their garden...can anyone identify this film ? Thanks !