How to Germinate Coleus Seeds Successfully

Overview

Coleus (Plectranthus scutellarioides) dazzles with foliage ranging from pale green and white to fiery reds and deep purples. These versatile plants thrive in beds, containers, and window boxes, with cultivars suited to both sun and shade. Starting seeds indoors in early spring yields robust transplants ready for the garden after the last frost.

Step 1: Prepare Seed-Starting Mix

Fill seed trays or cells to ¼–½ inch below the rim with moistened seed-starting medium. This lightweight mix retains moisture while minimizing disease risk.

Step 2: Sow Seeds

Plant 2–3 seeds per cell and cover lightly with ⅛–¼ inch of medium. Gently firm the surface and mist to settle seeds.

Step 3: Create a Humid Environment

Cover trays with plastic wrap and place in a warm (70°F+/21°C+) spot out of direct sun. A heat mat accelerates germination.

Step 4: Monitor Moisture

Check daily. The plastic should appear foggy but not have large water droplets. If condensation is heavy or soil feels soggy, poke ventilation holes. Mist lightly to maintain even moisture.

Step 5: Transition Seedlings

Remove plastic once seedlings emerge (5–10 days). Move to appropriate light conditions for your cultivar—check seed packet for specifics.