Great sentence! It is correct.
Original: Bees pollinate flowers, so apple trees have juicy apples in summer.
Why this is okay:
- There are two complete ideas: (1) bees pollinate flowers and (2) apple trees have juicy apples in summer. The word "so" connects these ideas and the comma before "so" is fine here.
- "Pollinate" means bees move pollen from one flower to another so the flowers can make fruit.
- "In summer" tells us when the apples are juicy.
Small improvements (optional):
- Clearer: Because bees pollinate flowers, apple trees grow juicy apples in the summer.
- Shorter: Bees pollinate flowers, so apple trees grow apples in summer.
Both your original and these versions are correct. Nice work!