Seeds are living organisms that require specific storage conditions in order to remain capable of producing healthy, vigorous plants. High quality seeds are essential to successful vegetable gardening.
While seeds begin losing their viability from harvest, with proper conditioning and storage, some may last years. Many vegetable types will maintain germination rates of at least 50% for ten or more years. For commercial vegetable production, the following list provides some guidance:
1 year - Onion, Okra
2 years - Beet, Pepper, Leek
3 years - Asparagus, Bean, Carrot, Celery, Lettuce, Pea, Spinach, Tomato
4 years - Cabbage, Cauliflower, Brussels Sprouts, Swiss Chard, Kale, Squash, Pumpkin, Radish, Turnip, Rutabaga
5 years - Cucumber, Muskmelon, Watermelon
When storing your seeds, be sure to keep them consistently cool and dry. Temperature and moisture are the primary factors that cause seeds to lose their ability to germinate.
Excessive seed moisture increases its respiration rate, can contribute to the growth of micro-organisms, attract insect attack, and reduced viability. Most commercial seeds are dried to less than 10% moisture soon after harvest and held in dry storage during packaging and distribution.
Like moisture, temperature has an influence on the seed's respiration rate. As the temperature increases, so does the respiration rate.
For short-term storage (one year to eighteen months), storing seeds at 35 to 50 degrees Fahrenheit and an air relative humidity of 30 to 40% is desired. The rule of thumb for good seed storage conditions is when degrees F + RH >= 100; the further you can go below 100, the better.
Aside from the conditions mentioned above, here are a few more guidelines:
Store in the coolest, driest location available to you avoiding temperatures over 70 degrees Fahrenheit. These conditions are easily met by placing a small packet of desiccant (which maintains a dry environment) into a tightly sealed, airtight (not airless), glass container and placed in your refrigerator.
Make sure that the storage containers are moisture-proof.
Maintain a fairly constant temperature.