How to Store Seeds | Keep Them Viable For Years

Store seeds in a cool, dry, dark place inside airtight glass or metal containers with a desiccant to keep them viable for one to several years.

A jar of saved seed is a promise to next spring’s garden — kept with three conditions: temperature, moisture, and light. Get those right and your tomato seeds will sprout three seasons from now. Get them wrong and you’re planting dead weight.

Temperature: The 40°F Sweet Spot

Seeds store longest at 40°F (4°C) or lower, but anything 32°F–55°F (0°C–13°C) works. The refrigerator holds a steady 40°F and protects seeds from temperature swings. A cold basement or north-side closet works too, as long as it stays consistently cool year-round. Freezers are not recommended unless seeds are bone-dry; residual moisture turns into ice crystals that rupture cell walls. If you must freeze, dry seeds for at least two extra weeks and seal in glass first.

Moisture: Keep It Below 40% RH

Target relative humidity (RH) under 40%; 60% is the absolute ceiling. Above 100, mold, rot, or premature sprouting will find your seeds. Use a desiccant in every container. Silica gel packets work perfectly. No packets? Wrap 1–2 tablespoons of powdered milk in a tissue and drop it in. Replace desiccant once a year or when damp.

Containers and Light: Airtight and Dark

Glass Mason jars with tight-sealing lids are the gold standard. Metal tins work well too. Plastic zipper bags are acceptable if you squeeze out all air and check for moisture, but are less reliable over multiple seasons. Store containers in total darkness — light triggers germination, and even indirect daylight degrades seed quality. Opaque containers dodge the issue; if using clear glass, keep jars inside a cardboard box or closed cabinet. For long-term storage, see our tested containers for storing seeds.

Preparation: Dry Before You Store

Seeds straight from the garden are too wet. Spread on paper towels or screens in a warm, airy spot out of direct sun for 1–2 weeks. Tomatoes and cucurbits need fermentation first: soak seeds and pulp in water for five days, rinse, then dry. For peas, beans, and peppers, pick at full ripeness and air-dry. Rinse and dry again. The extra step is worth it if you’ve had disease trouble.

The Condensation Trap

The most common mistake: pulling a cold jar out of the fridge and opening it immediately. Warm air hits cold glass, moisture condenses on seeds. Let every container sit on the counter for an hour before opening. To plant, remove only what you need, reseal, and return jar to the fridge.

Exceptions: Seeds That Must Stay Damp

Walnuts, oaks, magnolias, and other “recalcitrant” seeds die if dried out. Store these in damp sand, coir, or a sealed plastic bag at 41°F (5°C). They’re short-lived — plant the following spring rather than saving for years.

Common Mistakes to Avoid

• Storing seeds before fully dry — test by bending; if it flexes instead of snapping, it needs more drying time.
• Using garages, sheds, or spaces where temperature and humidity swing with weather.
• Opening cold containers before they reach room temperature.
• Freezing seeds that aren’t 100% dry.
• Storing in clear containers on a sunny windowsill or bright room.

A quick germination test before planting old seeds: dampen a paper towel, sprinkle ten seeds on it, roll up, and keep in a warm spot for a week. If 7 of 10 sprout, your storage is working.