Seed Preparation Techniques to Maximize Germination of Pacific Northwest Conifers

Stratification, the historical name for moist chilling seeds to mimic natural processes, is the primary means of releasing seed dormancy in most Pacific Northwest conifer species. This treatment removes internal, or physiological, dormancy, the main dormancy mechanism, but can also address external, or seed coat-imposed, dormancy by leaching chemical inhibitors and weakening mechanical restraints of the seed coat. Nursery personnel intentionally move seeds through the three stages of germination: hydration, activation, and emergence. To fully release dormancy, technicians target specific moisture contents during the activation phase. Maintaining seed in a surface dry condition for part, or all, of the activation phase allows for removal of dormancy while minimizing risks such as excess respiration, mold development, and premature germination. Several “advanced” techniques to maximize germination parameters include: extended stratification, delayed dryback during stratification, mid-stratification grading, and thermal priming (seed warming). These techniques do not involve specialized equipment but require close attention to detail to realize their potential. This paper is based on a webinar presentation given September 16, 2020 as part of the 2020 North American Forest and Conservation Nursery Technology Webinar Series, which can be viewed at https://vimeo.com/458771879. An accompanying online bulletin board is at https://padlet.com/nabilkhadduri/seedgermwebinar.

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Author(s): Nabil Khadduri

Publication: Tree Planters' Notes - Volume 64, Number 1 (2021)

Volume: 64

Number: 1