Why do some seeds fail despite optimal temperatures?
Written by
Paul Reynolds
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.Having adequate warm temperatures does not equate to successful germination alone. While appropriate temperatures are important, seeds rely on optimum conditions beyond heat. Oxygen availability, light, and soil structure are equally important. Recognizing the interactions can alleviate much of the frustration when working in the garden.
Seeds are killed by *oxygen deprivation* in saturated soils. Water occupies the air pockets that roots require for respiration. I had my first failure with an entire crop of lettuce before I figured out how to get proper drainage. Use pots with holes drilled in the bottom. Mixing perlite into heavy soils may help. Allow the top of the soil to dry out slightly before watering again.
Light Management
- Surface-sow light-dependent seeds: Lettuce, petunias
- Bury darkness-preferring seeds: Tomatoes, peppers
- Use light meters: Ensure 200-400 μmol/m²/s intensity
Soil Preparation
- Screen soil: Remove clumps before planting
- Top-dress with vermiculite: Prevents surface crusting
- Maintain crumb structure: Add organic matter annually
Seed Viability Assurance
- Float test: Discard seeds floating in water
- Cool storage: Keep at 40°F with silica gel packs
- Germination trials: Test 10 seeds on damp paper towels
When soil is compacted, it squashes the roots that are trying to emerge. Heavy clay soils tend to form thick crusts that can become impenetrable, especially after it rains. I now add compost on an annual basis to maintain the loose texture. I try not to walk on the planting beds. Use vermiculite to cover seeds rather than using dense soil that will crust in a thick layer.
Seed viability deteriorates each year, depending on the specific storage method. For instance, tomato seeds will remain viable for four years, while onion seeds will last for only one year. If your seeds are expensive or valuable, it's a good idea to have them tested for viability. Store seeds in airtight jars with desiccants in a cool, dark location for the longest possible duration to maintain viability.
Regional factors exacerbate these challenges. Fungal diseases thrive in humid regions that exhibit damp soils, while arid areas frequently experience crust formation. Modify your techniques to fit your local conditions for reliable results. Observe the crop daily, and when problems arise, take prompt action to correct the issue.
Read the full article: Seed Germination Temperature Mastery Guide
