Sweet Peas: How to Plant, Grow, and Care for Sweet Pea Flowers | The ... After you dig the trench, make holes with a pencil, drop in the seeds, and press down on the soil to firm it and shut out any light. Before planting, soak the seeds in water for 24 hours. Then nick the seeds with a nail file before planting to speed sprouting. You do not need to soak seeds in a temperate climate.