From Longman Dictionary of Contemporary Englishplant an idea/doubt/suspicion (in somebody’s mind)plant an idea/doubt/suspicion (in somebody’s mind)BELIEVEto make someone begin to have an idea, especially so that they do not realize that you gave them the idea Someone must have planted the idea of suicide in his mind. → plant
Examples from the Corpus
plant an idea/doubt/suspicion (in somebody’s mind)• Their conversation had planted doubts in Dennis' mind about the partnership. 