Mullein seeds germinate best when exposed to a period of cold, moist conditions (cold stratification). Direct sow mullein seed outdoors in fall where they will germinate the following spring. Seed can also be started indoors in spring 6 weeks before the last frost. If started indoors, cold stratify seeds in a refrigerator for 4-6 weeks prior to planting. Mullein seeds require light to germinate. Sow seeds 8-12" apart on the soil surface and press lightly to settle. Seeds will sprout in 12-15 days. Transplant seedlings outdoors once danger of frost has passed. Thin seedlings so that mature plants are 20-24" apart.