Cascading Plants That Spill Over Pots, Beds, Walls & Borders Gardening Know How Planting Instructions for Hibiscus Flower Seeds Nigella is one of those flowers that actually prefers the cool soil of early spring. In Zone 6b, I start sowing my nigella seeds in late winter and continue sowing through early Zone 9 Planting Schedule What to Start Each Month Gardening Know How Seed Plants: Angiosperms Introductory Biology