Mixed Hydrangea Seeds Grow stunning blue, pink, and purple hydrangeas with these carefully selected seeds. Hardy perennials that are easy to grow and perfect for garden color or cut flower arrangements. Sowing: Direct sow in spring by pressing seeds into soil surface (they need light to germinate). Keep soil moist; germination occurs in 10-14 days. Or start indoors in peat pots with indirect sunlight. Growing: Needs consistent moisture and well-draining soil. Tolerates clay and rocky areas. Deadhead spent blooms to encourage more flowers. Cut back to 8-10" in winter dormancy. Harvesting: Cut stems when flowers just open and place in water immediately. Strip lower leaves. Excellent for fresh or dried arrangements—hang upside down in a warm, dark, well-ventilated space to dry.