Saving Old Seeds
Often, at this time of year, while gardeners enjoy their brief respite of downtime, they may begin taking inventory of the seeds they have stockpiled, ready to get them started in just a couple of short months. However, This begets the question, “How well will they grow for me?”
When determining seed viability, the two critical factors to consider are the length of time the seeds have been stored and the conditions in which they have been stored. Most vegetable and flower seeds will remain viable for at least one year if properly cared for. Depending on the plant type, some can last up to 10 years or longer.
Minimizing seed exposure to factors like moisture, heat, and temperature fluctuations is the key to successful long-term seed storage. Remember, just like your in-ground plants, seeds are still living organisms; they currently exist in a dormant state. Seed viability can be lost quickly under improper storage conditions, so it is essential to keep seeds dry and cool to preserve them.
Storing seeds in moisture-proof containers like sealed glass jars or vacuum-sealed bags provides an effective barrier against humidity, provided you have ensured thorough drying before sealing. However, even in optimal conditions, residual moisture can cause mold growth or lead to premature deterioration.
Once properly containerized, seeds should ideally be stored in a refrigerator at temperatures just below 40°F. Freezing can be particularly effective for long-term seed preservation, as it slows the metabolic processes within the seeds, but home gardeners should not commonly practice this. Extra care must be taken to ensure the seeds have internally dried enough before storage to mitigate rupturing and killing the seeds. Since this would then require finite measurements and recordings of liquid weight within the seeds with highly sensitive scales, the better (easier) option is to avoid freezing and keep the seeds at least at just above 32°F.
Despite following best storage practices, seed viability does still experience a natural decline over time. To test viability, one should start by selecting 15 or so seeds from a batch and placing them on a damp paper towel. Fold the paper towel to encase the seeds, then position it in a consistently warm spot like a sunny window. Check the seeds after 7-10 days to determine how many have sprouted and determine your germination rate. Seeds with high germination rates can be sown with little worry. Those with lower rates may require adjustments to your planting plan, with more seeds planted more densely.
Understanding seed viability can benefit both the novice and experienced gardener! Proper storage will preserve seed stock and reduce wasted time, effort, and money by eliminating the need to buy new seeds annually. For those who save seeds from their gardens, these practices can be followed as well; remember that the practice is usually not recommended for vegetables, as cross-pollination on non-self-pollinating plants can generate strange hybrid vegetable seeds untrue to the parent plant specimens.
In any case, by investing a little time and care into preserving previously purchased seeds, gardeners can ensure a thriving and productive garden year after year.
by Anthony Reardon, Horticulture Small Farms Agent,2024