Seed Storage Basics

Before storing seeds, they should be dried but not over-dried. For long-term storage, well-matured seeds with a strong shell are best. Store seeds in a dry, cool place without fluctuations in temperature and humidity. Containers (such as bags, jars, etc.) should be labeled with the variety name, date, and other relevant information.

Humidity

Even when dormant, seeds continue to undergo life processes, though at a much slower rate. Moisture absorbed from the air, combined with the nutrients inside the seed, forms a soluble “food” that reacts with oxygen, releasing water and heat. If the air is too humid, seeds will use up their nutrient reserves and hormones too quickly, generating excess heat, which reduces their ability to germinate. Therefore, it’s important to minimize these metabolic processes during storage to extend the seed’s lifespan.

The ideal humidity level for long-term storage of hemp seeds is 6–9%. At higher humidity, seeds may start to rot, which is a common problem. A simple test: after drying, place the seeds in a sealed glass container. If condensation appears on the inside walls after a few hours, the seeds need further drying. Tests at different humidity levels show that seeds with a hard shell, such as hemp seeds, do not flatten but crack when struck with a hammer on a concrete surface if their moisture content is 8%.

To maintain stable humidity in a storage container, you can use silica gel or well-dried rice grains. The amount of silica gel should match the weight of the seeds. Typically, hemp seeds weigh between 0.01 and 0.02 grams, and our packets contain 0.5 g of silica gel. It’s recommended to store seeds in aluminum grip-seal bags, which should then be placed in jars along with the necessary amount of silica gel to keep humidity low. Be aware that excessive dryness can also harm seeds, so don’t overuse desiccants.

Temperature

Thoroughly dried seeds can withstand low temperatures that would be fatal to living plants. However, chilled seeds are very sensitive to temperature fluctuations and can be deactivated by brief exposure to warmth. Excess moisture in seeds can cause significant damage if they freeze.

Low temperatures slow down seed activity inside the shell, making them optimal for storage. You can also use very cold liquid nitrogen and cryogenic technology to store seeds for decades or even centuries.

Seeds should be stored in a cool or cold place. It’s better to keep them closer to the floor rather than the ceiling, where it’s usually warmer. However, the best place for long-term storage is a refrigerator or freezer, provided the seeds are dry and the container is airtight. The ideal temperature for storing seeds in a refrigerator is about 39°F (4°C).

A freezer is also excellent for long-term storage, but two important rules must be followed:

• Do not take seeds out too often or for too long, as temperature changes can damage them.
• If you want to use seeds stored in the freezer, do not open the container until the seeds have warmed to room temperature—otherwise, condensation may form on the seeds.

Light

Light can trigger the germination process. Additionally, the viability and health of seeds can suffer if they are exposed to light during storage.

Air

The protective shell or outer coat of seeds is never completely sealed and allows moisture and air to enter. Once air penetrates the outer shell, the seed receives a signal to start germinating. Viable seeds last longer in vacuum packaging, where all oxygen is removed.

Seeds with poor external protection almost never go dormant, as air and moisture are always present inside. This moisture and air cause hormone levels to drop, so these seeds do not store well for long periods.

Pests

Mold and Fungi

Mold and fungal spores (such as Pythium or Rhizoctonia) become active when moisture exceeds 10–15% and temperatures are above 59–68°F (15–20°C).

Insects

Surviving insects can seriously damage seeds during storage. A few pinches of diatomaceous earth is a safe, inexpensive, and non-toxic way to protect seeds from insects. Simply dust all seeds lightly before sealing them for storage. Diatomaceous earth is available at most garden supply stores.

Rodents

If not stored in glass or metal containers, seeds can become a feast for mice and other small rodents. Make sure to store seeds in metal or glass containers with proper labels.

Germinating Seeds After Storage

Most fresh seeds are highly viable, with about 95% germination. Seeds that have been stored for more than 1–2 years or have been transported often take longer to germinate or have lower germination rates, resulting in a higher percentage of weak plants or those with reduced immunity. Some seeds remain viable for five years or more if stored properly. If 50% or more of your stored seeds do not germinate, their average storage life has expired.

Do not disturb containers with seeds stored in the refrigerator until you are ready to use them. Allow them to warm to room temperature for at least 12 hours before soaking.