Plant asafoetida seeds in seed trays using rich, well-draining soil. Plant two or three seeds per compartment and cover with a thin layer of soil. Keep the soil moist and in a sunny location indoors or in a greenhouse.
Transplant healthy asafoetida seedlings when they are approximately 3 to 6 inches tall into their own 4- to 6-inch planting pot. Plant the seedlings the same depth as before. Continue to keep the soil moist and in a sunny location indoors until spring.
Transplant the asafoetida seedlings outdoors in the spring when the danger of frost has passed. Plant them about 24 inches apart in a sunny location. Asafoetida tolerates most soil types provided it has good drainage. Allow the soil to dry out before watering the plants again.
Apply a 2- to 3-inch layer of mulch in the fall before the first frost. Mulch protects the roots, especially during the first winter. When new growth commences in the spring, begin to water it again. It will take at least four years of similar care before the roots can be harvested to make the asafoetida spice.