1. Talking and singing to the vegetables is good for the vegetables.

Question

2. Talking and singing to the vegetables is good for the vegetables and produce.
3. Talking and singing to the vegetables is good for the produce.
4. Talking and singing to the vegetables is good for themselves.
5. Talking and singing to the vegetables is good for them.
[Which ones are grammatical? Which ones are commonly used? Do we have to use 'is'? How about 'are' instead of 'is'?]

Answer 1

#s 1 and 5 are correct.

Since "produce" was not mentioned earlier in the sentence, I wouldn't use 2 or 3.

#4 is incorrect since the vegetables didn't sing to themselves.
http://english-zone.com/members/grammar/reflex01.html