Plot · field guide
How to Store Seeds Long Term: Building a Survival Seed Bank
A survival garden runs on seed. If the store shelf is empty and your seed rack is empty too, you have a lawn, not a food supply. The fix is a seed bank you control: the right seeds, stored the right way, tested so you know they still grow. This guide shows how to store seeds long term, how many to keep, which crops last and which do not, and a two-dollar test that proves your stock before you bet a season on it.
Photo: Photo: ShebleyCL (CC BY)
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The four things that kill stored seed
A seed is alive but resting. Every seed is a tiny plant on pause, and four things wake it up or wear it out early: heat, light, moisture, and air. Control those four and a packet that would fade in a year can hold for several. Ignore them and even fresh seed dies fast.
The rule to remember is cool, dark, dry, and sealed. Seed storage experts often use a rough guide: the temperature in Fahrenheit plus the percent humidity should stay under 100. A cool closet at 60 degrees and 30 percent humidity clears that bar. A hot garage at 90 degrees does not, which is the single most common way home seed dies.
- Cool: aim for a steady spot under 60 degrees Fahrenheit. Every drop of about 10 degrees roughly doubles storage life.
- Dark: light triggers some seeds and degrades others, so store in an opaque box or tin.
- Dry: moisture is the biggest enemy. Toss a silica-gel desiccant packet in the jar to pull down humidity.
- Sealed: an airtight jar or Mylar bag keeps out damp air and pantry pests. Keep seed in its labeled paper envelope inside the sealed container.
Cool, dark, dry: how to actually store them
Start simple. For a year or two of storage, paper packets inside a sealed glass jar or a lidded plastic tote, kept in the coolest, driest room in the house, is enough. Add a silica-gel desiccant packet to each jar and label everything with the crop and the year, because you will not remember in eighteen months.
For the long haul, put the seed in the fridge or freezer. Cold, dry storage is how seed banks hold varieties for decades. Two hard rules make it work: the seed must be dry first, because moisture that freezes will rupture the seed, and the jar must be fully sealed so it does not pull damp air as it warms. When you take a jar out, let it come to room temperature before you open it, so water does not condense on the cold seed.
- Fridge (about 40 degrees F): adds years to most vegetable seed. Best all-purpose long-term spot.
- Freezer (0 degrees F): best for the longest storage, but only with fully dried seed in an airtight jar.
- Desiccant: a silica-gel packet or a tablespoon of powdered milk in a tissue keeps the inside dry.
- Let sealed jars warm to room temperature before opening to stop condensation on the seed.
How many seeds to stockpile, and which kind
The kind of seed matters more than the count. Buy open-pollinated or heirloom varieties, never hybrids. Open-pollinated seed grows true to the parent, so you can save seed from your own harvest and replant it next year for free. Hybrid seed, labeled F1, does not come back true, so a hybrid stockpile runs out the day you plant the last packet. Open-pollinated seed turns a one-time purchase into a supply that renews itself.
For quantity, think in full seasons, not single plantings. Plan enough seed to plant your whole survival garden at least twice over, because a late frost, a flood, or a pest wipeout can force a full replant. A packaged open-pollinated survival seed vault is the easy on-ramp: it bundles a balanced set of non-hybrid staples in one sealed kit. Then let your saved seed take over so you stop depending on the seed rack entirely.
- Choose open-pollinated or heirloom seed so you can save and replant. Skip anything labeled F1 hybrid.
- Stock enough to plant your full garden two to three times over to survive a failed planting.
- Lean on high-value staples first: dry beans, peas, squash, tomatoes, greens, and root crops.
- Rotate your stock. Grow some out each year, save fresh seed, and refresh purchased packets every few years.
How long seeds last, by crop
Not all seed ages at the same rate. Onion and parsnip seed fade fast, while tomato and squash seed can outlast a hard year with margin to spare. The ranges below reflect university extension seed-viability tables for seed kept cool, dark, and dry. Stored warm or damp, cut these numbers roughly in half.
These are planning numbers, not promises. Seed slightly past its range often still grows, just at a lower germination rate, which is exactly why the germination test in the next section matters.
- Onion, leek, parsnip: about 1 year (university extension seed-viability tables).
- Corn, okra, pepper: about 2 years (university extension seed-viability tables).
- Bean, pea, carrot: about 3 years (university extension seed-viability tables).
- Tomato, pumpkin, chard: about 4 to 5 years (university extension seed-viability tables).
- Cucumber, squash, melon, lettuce: about 5 to 6 years (university extension seed-viability tables).
Test your seed before you bet a season on it
Old seed is not dead seed, but you should never guess. A germination test tells you exactly what share of a packet will sprout, so you can sow thicker to make up for it or replace the packet before planting season. It costs almost nothing and takes about a week.
Do the math on the result. If 8 of 10 seeds sprout, that packet is about 80 percent viable, which is fine. If only 3 come up, that is 30 percent, and you either sow three times as thick or buy fresh. Run this test every spring on your oldest packets and you will never lose a planting window to seed you assumed was good.
- Count out 10 seeds from the packet so the math is easy.
- Space them on half a damp paper towel, fold the other half over, and slide it into a labeled zip bag.
- Keep the bag somewhere warm, around 70 degrees F, like the top of the fridge. Keep the towel damp, not soaked.
- Check daily for 7 to 10 days. Count how many sprout: that number times 10 is your percent germination.
Questions, answered straight
It depends on the crop and the storage. Kept cool, dark, and dry, university extension seed-viability tables put onion and parsnip at about 1 year, corn at about 2, beans and peas at about 3, tomato at about 4 to 5, and cucumber and squash at about 5 to 6 years. Stored warm or damp, expect roughly half those ranges. A germination test tells you what a given packet can still do.
Get them fully dry, then seal them airtight and keep them cold. Put labeled paper packets in a glass jar with a silica-gel desiccant packet, and store the jar in the fridge at about 40 degrees or the freezer at 0 degrees. The seed must be dry before it freezes, and the jar must warm to room temperature before you open it so water does not condense on the seed.
Enough to plant your whole survival garden two to three times over, so a failed planting or a wipeout does not leave you empty. Just as important, buy open-pollinated or heirloom seed instead of hybrids, because you can save and replant your own seed each year. That turns a one-time stock into a supply that renews itself instead of running out.
A simple check of how many seeds in a packet will still sprout. Lay 10 seeds on a damp paper towel, fold it over, seal it in a labeled zip bag, and keep it warm at about 70 degrees for 7 to 10 days. Count the sprouts: if 8 come up, the packet is about 80 percent viable. Low results mean sow thicker or replace the seed before planting season.