Have you ever planted leftover seed from last year and had almost nothing come up? It happens to all of us, and most of the time the seed wasn't bad. It was stored in the wrong place. Seeds are living things, resting until conditions are right to grow. Treat them well and many will stay good for years. In this guide, you'll learn what damages seeds, how to store them, and how long different kinds typically last.
What makes seeds lose their viability?
Seeds slowly age no matter what, but three things speed it up a lot:
- Moisture: Humidity is the biggest enemy. Damp seeds use up their stored energy, and they can mold or even start to sprout.
- Heat: Warm temperatures speed up aging. A hot car, a sunny windowsill or a summer garage can cut a seed's life short.
- Swings in conditions: Going back and forth between warm and cool, or damp and dry, stresses seeds over time.
A simple rule: the cooler and drier you keep seeds, the longer they last.
How should you store leftover seeds?
- Keep them sealed. Our seed packets are mylar-lined and heat-sealed, which protects the seed until you open them. After opening, fold the top over and clip it shut.
- Use an airtight container. Place opened packets together in a glass jar with a tight lid or another airtight container.
- Add a desiccant. Toss in a silica gel packet, or a tablespoon of dry rice or powdered milk wrapped in a tissue, to soak up moisture.
- Find a cool, dark spot. A closet, a basement shelf or the refrigerator all work well.
- Label everything. Write the variety and year on each packet so you know what to use first.
Should you store seeds in the fridge?
The refrigerator is a great choice, since it stays steady at around 40°F. The key is keeping seeds airtight, because fridges can be humid. When you take the jar out, let it warm to room temperature before opening so moisture doesn't condense on the cold seeds.
Freezing works too for dry seed, but for most home gardeners, a cool closet or the fridge is simpler and plenty good.
Where should you avoid storing seeds?
- The garage or shed, where temperatures swing widely.
- A greenhouse or sunny windowsill, which get far too warm.
- The kitchen above the stove or near the dishwasher, where heat and steam build up.
How long do seeds last?
Even with great storage, some seeds naturally last longer than others. These are typical ranges for well-stored seed:
- 1 to 2 years: Onions, leeks, parsnips, chives and sweet corn. Buy these fresh most years.
- 2 to 3 years: Peppers, beans, peas, spinach and carrots.
- 3 to 5 years: Lettuce, kale, cabbage, broccoli, beets and squash.
- 4 to 6 years or more: Tomatoes, cucumbers, melons and radishes.
Older seed often still sprouts, just at a lower rate. If you're unsure, do a quick germination test before planting season.
How to test old seeds
Place 10 seeds on a damp paper towel, fold it up and seal it in a plastic bag. Keep it somewhere warm and check after the usual germination time. If 8 sprout, you have about 80% germination. If fewer come up, just sow a little more thickly or pick up a fresh packet.
Stock up with confidence
Stored cool, dark and dry, most seed will be ready and waiting when spring arrives, so it's safe to shop early. All our seeds are non-GMO and USA grown, and I pack and seal every packet myself here in Minnesota. A few favorites that store especially well are Brandywine Red tomato, Marketmore cucumber and Cherry Belle radish.
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