Surface Sowing Seeds

How to sow seeds that require light to germinate by placing them on the soil surface.

What is Surface Sowing?

Surface sowing is a planting technique where seeds are placed on top of the growing medium rather than buried. This method is essential for seeds that require light to trigger germination ΓÇö a mechanism evolved to ensure seeds only sprout when they are close enough to the surface to reach sunlight.

Which Seeds Need Surface Sowing?

Many small seeds have evolved to germinate only when exposed to light. Common categories include:

  • Herbs: Basil, oregano, thyme, lavender
  • Flowers: Petunias, snapdragons, coleus
  • Trees: Birches (Betula), some maples
  • Shrubs: Some rhododendrons, azaleas
  • Wildflowers: Many native species

Step-by-Step Surface Sowing

  1. Prepare the medium: Use fine, sterile seed-starting mix. Moisten thoroughly before sowing.
  2. Fill containers: Use shallow trays or pots with drainage holes.
  3. Sow seeds: Sprinkle seeds thinly and evenly on the surface. Do not cover with soil.
  4. Press gently: Use a flat board or your fingers to press seeds into contact with the medium.
  5. Mist gently: Water with a fine mist spray to avoid displacing seeds.
  6. Cover with plastic: Use a humidity dome or plastic wrap to maintain moisture.
  7. Provide light: Place under grow lights or in bright indirect light.
  8. Remove cover: Once germination begins, remove plastic to allow air circulation.

Important Considerations

  • Temperature: Most surface-sown seeds germinate best at 18-24┬░C (65-75┬░F)
  • Moisture: Keep consistently moist but not waterlogged
  • Light: 12-16 hours of light per day for best results
  • Airflow: Good circulation prevents damping off disease
  • Thin seedlings: Once true leaves appear, thin to prevent overcrowding

Common Mistakes to Avoid

  • Burying light-dependent seeds ΓÇö they will not germinate
  • Using heavy soil that compacts and blocks light
  • Overwatering, which can wash seeds away or cause rot
  • Placing in darkness before germination occurs

Transplanting Surface-Sown Seedlings

Surface-sown seedlings are often delicate. When they have 2-3 true leaves, gently transplant to individual pots. Handle by the leaves, never the stem. Keep in shade for a few days to reduce transplant shock.

Applies to