All credit for the following goes to u/stack_man on r/BugFables



I bequeath to thee forbidden knowledge of the Golden Seedlings. Spoilers ahead. You have been warned.

Requirements:
- Ice Rain
- Seedling Affinity

Recommended:
- Lots of TP
- Victory Buzz
- EXP Booster (If grinding EXP)
- Quick Flea

First, gain access to the Seedling Haven. It is west from the explorer's association and north, across the river. Defeat the boss here and you'll be ready for farming.

If you only want Tangy Berries:
1. Encounter a seedling. If there are any Golden Seedlings, defeat it with Ice Rain, otherwise, flee and re-encounter.
2. Once all seedlings are defeated, use the ant compass, teleport to the ant plaza, and walk back to the haven.
3. Repeat steps 1-2

If you also want EXP:
1. Encounter a seedling.
2. Repeatedly flee and re-encounter the seedling until all seedlings are golden. (Any that appear golden once will remain golden every encounter)
3. Defeat the golden seedlings with ice rain (each icicle can hit two enemies)
4. Once all seedlings are defeated, use the ant compass, teleport to the ant plaza, and walk back to the haven.
5. Repeat steps 1-4

Level ups will easily fill up your TP, eat Tangy Berries or use the inn if you need to.

Bonus tip: Leave berries on the ground. After fleeing, touch one to immediately cancel invincibility frames and get another encounter.