In Jain Dharma, potatoes and onions are generally avoided because they are root vegetables.

Main reasons:

• Ahimsa (non-violence): Root vegetables contain many small living beings and can harm more life when uprooted.
• Uprooting kills the whole plant: Unlike fruits or leaves, taking a root vegetable removes the entire plant from the earth.
• Stimulate harmful passions: Onions and garlic are also considered to increase restlessness, anger, and desire, which is not helpful for spiritual discipline.

Jain view:

Jains try to eat foods that cause the least harm to living beings and support a calm, pure, and disciplined life.

That is why many Jains avoid:

• potatoes
• onions
• garlic
• other root vegetables

If you want, I can also explain the Jain reasons in very simple Hindi or Gujarati.