Emmalea Ernest, Extension Fruit & Vegetable Specialist; emmalea@udel.edu
If you have excess vegetable seed that you would like to plant in the future, it can remain viable for next year, the next or maybe longer with proper storage. The longevity of carryover will depend upon the initial seed quality, the crop species and storage temperature and humidity.
Seed Quality
Seed lots with good germination and vigor are the best candidates for successful carryover. If a seed lot had low germination or low vigor in the current season, don’t plan to use it in future plantings. Seed that has been primed to promote even germination or heat treated for disease prevention is also not recommended for carryover.
Crop Species
Seeds of some crops last longer than others. The table below shows the relative seed longevity for some common vegetables and herbs. Short longevity crops should not be carried over for more than one or two years with room temperature storage. Seed of other crops can remain useful for five or more years with proper storage.
Relative Longevity of Seed for Common Vegetables and Annual Herbs
| Crop | Relative Seed Longevity |
| Basil | Long |
| Beet | Long |
| Muskmelon/Cantaloupe | Long |
| Pea | Long |
| Radish | Long |
| Spinach | Long |
| Tomato | Long |
| Cucumber | Medium Long |
| Okra | Medium Long |
| Squash (C. moschata) | Medium Long |
| Squash (C. pepo) | Medium Long |
| Watermelon (seeded) | Medium Long |
| Eggplant | Medium |
| Snap Bean | Medium |
| Squash (C. maxima) | Medium |
| Carrot | Short |
| Celery | Short |
| Cole Crops | Short |
| Dill | Short |
| Lettuce | Short |
| Onion | Short |
| Parsley | Short |
| Pepper | Short |
| Sweet Corn | Short |
Table classifications based on research reported in Walters, Christina, Lana M. Wheeler, and Judith M. Grotenhuis. “Longevity of seeds stored in a genebank: species characteristics.” Seed Science Research 15.1 (2005): 1-20.
Storage Conditions
Storage temperature and humidity impact seed longevity. The best storage conditions for most seeds are low temperature, low humidity and low light. Seeds stored at controlled room temperature (~70 °F) and humidity (~50%) will remain useful for 2 to 5 years. Seeds stored in low humidity and refrigerated temperatures (~37 °F) will last longer. Storing carryover seed in a freezer is not necessary to extend longevity under most circumstances.
Maintaining cool temperature and low humidity is important. Even brief exposure to high temperature or humidity, such as leaving seeds in a greenhouse, can reduce longevity. Airtight bags, containers or jars can help to keep seeds at low humidity. Seeds in paper packets can be stored inside larger airtight bags or containers to protect against humidity fluctuations.