Flower seeds lose their ability to sprout successfully, a property known as viability. Seeds are living embryos in a state of suspended animation, and while they can remain dormant, they are not immortal. Over time, the internal biological systems degrade, and external environmental factors accelerate this natural aging process. Understanding these factors is the first step toward preserving your seed collection for future planting seasons.
The Science of Seed Viability Loss
Seed deterioration is a slow process that occurs even in the dry, quiescent state. Although a seed appears inactive, its cells gradually use stored energy reserves through low-level respiration. This slow metabolism, coupled with the accumulation of molecular damage, causes viability loss.
The primary mechanism of damage is oxidative stress, caused by reactive oxygen species (ROS) within the seed. These unstable molecules attack and degrade the cell’s macromolecules, specifically the DNA, RNA, proteins, and lipids. Damage to the lipid-based cell membranes disrupts the cell’s integrity and its ability to function properly when germination is attempted.
The rate of this internal decay is largely driven by moisture, temperature, and light. High moisture levels activate mitochondrial respiration, which rapidly increases the production of damaging ROS and can also encourage fungal growth. Elevated temperatures speed up chemical reactions, accelerating the consumption of stored food and the accumulation of molecular damage. Exposure to light contributes to seed aging and should be avoided for long-term storage.
Maximizing Longevity Through Proper Storage
Proper storage follows the principle of “cool, dark, and dry.” The two most significant factors governing longevity are seed moisture content and storage temperature. The general guideline suggests that the sum of the storage temperature in Fahrenheit and the relative humidity percentage should not exceed 100 for safe short-term storage.
A moisture content of less than 8% is beneficial for long-term preservation of many orthodox seeds. Seeds should be thoroughly air-dried before storage, potentially using a desiccant like silica gel packets or a small amount of powdered milk placed in the storage container. Storing seeds in temperatures between 35°F and 40°F is recommended, which corresponds to the temperature range of a standard refrigerator.
Since refrigerator environments often have high relative humidity, seeds must be placed in moisture-proof containers to prevent absorption. Sealed glass jars or airtight plastic containers are preferred over simple paper envelopes for this purpose. If using the refrigerator or freezer for long-term storage, the seeds must be completely dry and sealed tightly to prevent condensation when the container is taken out into warmer air. Storing the sealed containers in a dark location, such as a closet or drawer, protects them from light exposure.
Simple Tests for Seed Viability
If you have found a packet of seeds, you can perform a simple home germination test. This method, often called the paper towel test, provides a reliable estimate of viability. This test requires a representative sample of seeds, typically ten or twenty, which are placed on a moistened paper towel.
The paper towel should be damp but not dripping wet. This “seed sandwich” is placed inside a plastic bag or container and kept in a warm area, where temperatures are around 70°F. The bag should be left slightly ajar to allow for air circulation, which prevents mold growth.
After the expected germination period, count the number of seeds that have successfully sprouted. To calculate the germination rate, divide the number of sprouted seeds by the total number of seeds tested. A germination rate above 80% indicates viable seeds, while a rate below 50% suggests the seeds should be discarded.