Great little poem! Here is the corrected punctuation and a simple explanation you can understand.
Original:
During the dry months the grasses turn yellow. But once the rains fall, the grasslands turn green.
Corrected (one clear way to punctuate it):
During the dry months, the grasses turn yellow. But once the rains fall, the grasslands turn green.
If you want it on separate lines (still correct):
During the dry months, the grasses turn yellow. But once the rains fall, the grasslands turn green.
Why we changed it:
- Put a comma after "During the dry months," because those words tell when something happens. A comma helps our ear know to pause a little.
- Keep a period at the end of "the grasses turn yellow." because that is the end of a sentence — a full thought.
- Put a comma after "But once the rains fall," for the same reason: it tells when, and the comma gives a small pause before the rest of the sentence.
Tip: Read it out loud. Pause a little where you see commas, and stop at periods. That helps the poem sound clear and nice.