Ask them how they know this, and they will tell you that they learned (or their ancestors learned) by directly communicating with the spirit of the plants.
उनको प्रश्नले मलाई पछिसम्म लखेटिरहयो, के साँच्चै मलाई काँठबाहेक अन्य ठाउँको विषयमा ज्ञान छैन ?