Lecture 14: Plant Propagation Part 2

Seed Storage

  • Importance of proper seed storage after harvest.

  • Recommended conditions for seed storage:

    • Cool and dry location.

    • Refrigerators are often a good option.

Seed Selection

  • Awareness of healthy seeds:

    • Research specific plant species to understand what healthy seeds look like.

    • Use terms like "Acer palmatum seed" in internet searches for visual references.

  • Collect both good and bad seed samples for testing.

  • Conduct a germination test:

    • Importance of testing seeds to determine viability.

    • Referencing reading for detailed germination testing instructions.

  • Consideration of seed dormancy:

    • Understanding dormancy types when selecting seeds.

Germination Testing

  • Performing a germination test:

    • Essential to understand viability and avoid non-germinating seeds in the future.

Seed Storage Techniques

  • Proper seed moisture levels:

    • Ideal moisture level for seeds to withstand impact (light tapping should shatter, not mash).

    • Techniques for checking moisture:

      • Seed moisture meters.

      • The "bite test": hard seeds vs. those that indent when bitten.

  • Use of plastic bags:

    • Effective for proper storage.

    • Risks of moisture accumulation leading to mold if seeds are not adequately dried.

  • Ziplock or vacuum sealing:

    • Prevents moisture ingress and excessive drying.

  • Prevention of excessive drying in refrigerators:

    • Explanation of dehumidifying systems in modern refrigerators.

  • Freezing seeds:

    • Not recommended due to cellular destruction and creation of mush.

  • Paper bags:

    • Use of wax-coated paper bags as a forgiving storage method.

    • Importance of labeling and dating seeds.

Dormancy Types

  • Definition of dormancy:

    • A mechanism to prevent germination until conditions are optimal.

  • Types of dormancy:

    • Physical Dormancy:

      • Characteristics: hard, waterproof seed coat (e.g., acorns).

      • Mechanism: moisture must penetrate the seed coat.

      • Scarification methods:

      • Sandpaper or light abrasion to weaken the seed coat.

      • Commercial acid baths (not for home use).

      • Hot water soaks as a practical home method.

    • Temperature-Dependent Dormancy:

      • Chilling requirement for seeds that need exposure to cold temperatures to germinate (typically below 40°F).

      • Stratification:

      • Process of exposing seeds to moisture and cold to fulfill chilling requirements, can be done naturally or in refrigerators.

      • Chilling duration:

      • Typically 6-8 weeks, can extend to 12 weeks for certain species.

      • Some plants require heat from natural forest fires for seed release (heat-induced dormancy).

    • Underdeveloped Embryo Dormancy:

      • Content: seasonal factors can delay embryonic maturity.

      • Mechanism: warmth induces growth but may regress due to subsequent cold spells.

      • Example species requiring long-term warmth for embryo maturation.

    • Chemical Dormancy:

      • Common in fleshy fruits, seeds need to be cleaned of flesh and chemicals for successful germination.

      • Common methods include warm water soaks.

  • Combination Dormancy:

    • Many plants exhibit multiple dormancy types requiring tailored treatment approaches.

Germination Requirements

  • Germination Process:

    • Seed must absorb moisture, require oxygen, and optimum temperature.

      • Ideal soil temperature (around 65°F).

  • Soil moisture management:

    • Needs to be moist but not excessively wet to avoid drowning seeds.

  • Light requirements:

    • Small seeds typically need light for germination; surface sowing is preferred.

Seed Media for Germination

  • Clean and sterile media is vital for seed germination.

  • Recommended seed mix components:

    • Pulverized peat moss, vermiculite, perlite.

  • Importance of moisture retention without excessive wetness.

  • Labeling and tracking seed metadata for consistency in growth.

Planting Techniques

  • Recommended planting depth:

    • Follow specific seed packet instructions or general rules:

    • Plant 2-4 times the seed diameter or thickness.

  • Importance of not planting too deep:

    • Small seeds must remain close to the surface to access light and germinate effectively.

  • Types of Germination:

    • Epigeal Germination (e.g., beans): cotyledons emerge above ground.

    • Hypogeal Germination (e.g., corn): leaves emerge below ground; the seed stays buried.

Damping Off Disease

  • Explanation of damping off disease: a common issue in seedlings caused by various fungal organisms.

  • Prevention strategies:

    • Using sanitized soil to mitigate disease risks.

    • Methods for home sterilization:

      • Microwaving seed media in Ziploc bags.

Seedling Care

  • Importance of maintaining ideal conditions during germination:

    • Keeping temperatures between 80°F-90°F.

  • Importance of transplanting at the right time:

    • Observe root development to determine transplant readiness.

  • Hardening Off: gradual exposure of seedlings to outdoor conditions to improve resilience.

  • Root development evaluations:

    • Healthy seedlings will have a mix of adequate and maximal root growth without being root-bound.