Planting tomatoes when one is planting seeds, appears to be a metonymy or synecdoche. Because the word “seeds” is replaced with the word “tomatoes”, a component of the plant could be a form of synecdoche.
But I believe it to be a metonymy. The tomato is the fruit of the plant Solanum lycopersicum, a member of the nightshade family, the plant itself is poisonous but its fruit is edible.
In my limited knowledge, I found a parallel example in the phrase "making babies", for sexual intercourse where the "result of the action is stated in place of the action" which would be metonymy so comparing "making babies" to "planting tomatoes" appears to be parallel.
So I am caught between metonymy and synecdoche. Does what I am saying make any sense?
Thank you for your time and assistance.