This research investigated why the medicinal mushroom Ganoderma lucidum cannot produce good quality mushrooms in second harvests from the same growing material. Scientists discovered that the mushroom releases organic acids during its growth that make its environment too acidic for healthy second growth. This self-poisoning effect helps explain why farmers must use new growing materials for each crop. Impacts on everyday life: • Helps mushroom farmers understand why they need fresh growing materials for each crop • Could lead to more efficient and sustainable mushroom cultivation methods • May reduce cultivation costs and waste in medicinal mushroom production • Provides insights that could improve the availability and affordability of this medicinal mushroom • Could contribute to developing methods for multiple harvests from the same growing material