Seed viability duration ranges from just one year to over eight decades depending on the crop. Onion seeds may fail after 1-2 years even with perfect storage. Tomato seeds can sprout after 80+ years when kept in ideal conditions. Knowing these numbers helps you plan when to use or replace your saved seeds.
I grew strong tomato plants from seeds I'd stored for five years in my basement. They sprouted at nearly 90% rates and produced a great harvest. But my two-year-old onion seeds from the same storage spot gave me almost nothing. Only a handful of seeds germinated out of the whole packet.
Seed longevity by species varies so much because of differences in seed structure and oil content. Seeds with more oils tend to go bad faster. Onions, parsnips, and corn have shorter storage lives. Tomatoes, peppers, and beans can last for decades when you treat them right.
USDA research shows that temperature and moisture control how long seeds last in storage. Every 10°F (5.5°C) increase in temperature cuts seed life in half. The same goes for moisture levels. Cool dry storage gives you the longest possible seed storage lifespan for every crop you save.
Scientists measure seed life using something called P50 values. This tells you how long until half the seeds in a batch will die under ideal lab conditions. Real-world storage usually gives shorter results but the rankings stay the same between crops.
Test your older seeds before planting season to avoid wasting garden space. Fold ten seeds into a damp paper towel and keep it warm for a week. Count how many sprout to get your germination rate. If less than 70% come up then you should plant extra or buy fresh seeds.
Replace short-lived seeds every year no matter how well you store them. Onions, parsnips, and leeks belong in this group. The cost of a new packet beats the risk of bare spots in your garden. Buy fresh or save new seeds of these crops each season to stay safe.
Long-lived seeds like tomatoes and peppers make great choices for building a seed collection. You can save them once and use them for years without worry. I still have pepper seeds from six years ago that sprout just as strong as they did the first season.
Read the full article: How to Save Seeds: A Complete Guide
