Growing Lobelia Erinus from seed is very rewarding! If starting Lobelia seeds outdoors, it will not begin to flower for two months after seed is planted. For quicker flowering, start the ground cover seed indoors 10 - 12 weeks before the last frost is due. Since the Lobelia seeds are very small, plant them on top of finely prepared soil without covering them. Transplant Lobelia seedlings after all danger of frost is passed, spacing them 6 inches apart. Remove flower spikes after blooming to produce further growth.