Divide an existing mint plant or acquire root cuttings from a friend, neighbor or nursery. How many you use is up to you; as a rough guide, try one mint plant every few feet in the moth-afflicted patch.
Fill up medium-sized plant pots with garden soil and plant the mint cuttings in them. The pots stop the mint plants overgrowing but allow free drainage and nutrient uptake.
Sink the pots into the ground between the afflicted vegetables or flowers. Water well the first day and during dry spells thereafter.
Snip leaves off the mint plants, crush them slightly and distribute in your pantry or closet. Replace the leaves every few days as the leaves wither and lose their aromatic, and repellent, scent.