Plant the stem of a cutting or roots from a divided plant directly in the ground in an area that receives dappled sunlight or in a 12-inch pot filled with well-draining potting mix. Space cuttings at least 15 inches apart.
Keep the pot in an area that receives full sunlight except direct afternoon sun if you're growing Mexican mint as a houseplant. Water the cutting regularly and deeply until it roots, usually about two weeks.
Water the established plant when the soil feels dry at a depth of 2 inches. Mexican mint tolerates lower water levels, so it can be left alone when planted outdoors if it rains regularly.
Fertilize Mexican mint every two weeks with 10-10-10 water-soluble fertilizer mixed into 1 gallon of water.
Spray the plant weekly with insecticidal soap if it's affected by spider mites or mealybugs. Stop spraying when the pests are gone.
Pinch or cut off leaves as needed for culinary use and wash them thoroughly before use.