This will ensure good distribution of water throughout the container while minimizing the chance of washing or splashing small seeds away. Water freshly seeded flats or trays gently. A strong force of water is likely to wash the seeds out of the growing medium. Watering should be evenly distributed across the flat. There is a tendency to miss the corners of flats, especially at the corners of benches.
Little water is needed before seedlings emerge.
Too much water will promote damping-off organisms. Once seedlings emerge, check them for dryness at least two or three times per day and water as needed. Never allow seedlings to wilt. Do not allow the greenhouse to get too hot. Too high a temperature will produce leggy plants.