Many people are aware that seeds must be kept dry and cool for their quality to be maintained in storage. However, the more critical questions are: What is the temperature, and how dry are the storage conditions required to be? While the responses to these questions differ among species of plants, some general guidelines can be applied to all seeds.
The two significant factors that impact the quality of seeds during storage are humidity and temperature. Sources must be kept in a storage environment that maintains a balance between moisture and temperature to preserve the quality of the seed and minimize the risk of seed degradation.
Scientists are also aware that the relative humidity ratio (as percent) along with temperatures (in degrees C) should be at most 100 to ensure secure storage of seeds. Therefore, if the temperature is exceptionally high, the relative humidity must be reduced and vice versa.
My master’s research at Oregon State University focuses on the most optimal preservation environment for hemp seeds ( Cannabis sativaL.) My advisor, Sabry Elias, and I are examining various ratios of relative humidity and temperature to see how they impact the quality of hemp seeds in storage.
Oregon researchers are examining storage conditions that will help hemp seeds grow the best. This is a typical hemp seedling that developed during the field Emergence test for vigor. The life tests will determine how plants will grow once they germinate. Credit: Grace Fuchs
Quality of seed refers to two aspects: viability and vigor. Viability refers to the seeds’ ability to germinate in ideal conditions. If you purchase a package of sources for your vegetable garden and find the percentage of germination on the bottom, this number was generated by a lab that created artificial “optimal conditions.”
We all know that weather forecasts and conditions before planting are perfect. Spilling hot coffee onto the seed packet before deciding to plant the seeds is possible. You may get an unexpected frost just a couple of days after planting. While your origins exposed to conditions that aren’t ideal may sprout, the seedlings may be malformed, uniform, or exhibit uneven and slow growth. Due to these variations, the viability of a seed does not always correspond with how the plant will develop.
Vigor is a measure of the capacity of seeds to develop into mature seedlings in an array of challenging conditions. It also affects the germination speed and the seeds’ consistency in a particular group. Thus, vigor tests can provide a more comprehensive overview of the seeds’ overall health and performance in the field compared to viability tests.
There is a lot of uncertainty among hemp seed farmers regarding maintaining high-quality seeds during storage. Many are concerned about the best conditions to store hemp seeds securely. They want to know how long hemp seeds can be kept.
I analyzed three storage facilities to provide the needed clarity to hemp seed farmers. Each of them had different ratios of temperature and relative humidity. We analyzed the differences in the quality of seeds over the course of 18 months.
Even though a seed may germinate, the storage conditions of the source can influence how well seedlings grow. A normal hemp seedling growing well on the left is shown here, with two abnormal seedlings on the right. This indicates that the seedlings on the right emerged from seeds stored in less-than-ideal conditions. This can influence the yield of hemp for farmers. Credit: Grace Fuchs
I also examined how different hemp varieties respond to these storage conditions over time.
I conducted seven initial quality tests (including viability and vigor tests) and then put the seeds into their respective storage areas. Each for four months, I took out the roots and analyzed their quality with those same tests. I repeated this procedure every 18 months (to gather enough data to allow an analysis of statistical data.)