Seed Storage
Alvin Yoshinaga, UH CCRT
Watch this video on Vimeo.
The following materials are also available for download:
Powerpoint Presentation: Home Seed Storage for Hawai‘i's Gardeners
Seed Storage: Internet Resources
How to make a miniature home seed bank
Longevity of seeds stored in genebanks: Key to Common Names
Guidelines for Successful Seed Storage
Storing Seeds in a Home Refrigerator
I work entirely on wild plants, but the principles I use are the same as those used for storing cultivated seeds.
Through proper seed storage techniques, you can get decades of life out of your stored seeds. Keeping seeds dry is key for successful seed storage.
There are three categories of seed: orthodox seeds, recalcitrant seeds, and intermediate seeds. Orthodox seeds can be dried down to very low moisture content and can be frozen and stored for decades. Recalcitrant seeds cannot be dried or frozen, and intermediate seeds are somewhere in between orthodox and recalcitrant seeds.
Most large seeds are recalcitrant, for example, coconuts, avocadoes, coffee, and papayas.
Worldwide, 93.2% of all seeds are orthodox and 5.4% are recalcitrant. In tropical climates, 70.2% of seeds are orthodox and 27.5% are recalcitrant.
Seeds don’t like hot or moist conditions. Drying 5–10% of seed moisture content greatly increases seed longevity. Reducing seed temperature from 25 C – 77 F to 20 C – 68 F increases the shelf life of seed by a factor of 11.
Refrigerating seed greatly increases shelf life. In an experiment which compared three storage techniques: dry storage over silica gel, vs. refrigeration, vs. freezing—all of the cold seeds were still viable after 10 years.
If you’re going to store seed, collect good, healthy seeds and store them at the right time.
Collect seeds when fully mature to maximize seed longevity.
Most countries have seed banks. The U.S. seed bank at Fort Collins stores seeds at 0 F, which is the same temperature as most home freezers. Freezing seeds allows for decades of storage.
Refrigerated storage works great for time spans of up to a few years. Store the seed in glass jars sealed with rubber gaskets, and replace the seals when they crack.
20% relative humidity provides ideal conditions for seed storage. A simple technique is to store newly saved seed in the refrigerator in a plastic container without a lid to dry. In about a month, put the lid on tightly, take the seeds out of the refrigerator, and let them come to room temperature. Then put them back into the refrigerator in a Ziploc bag. For freezing, use glass jars with rubber gaskets to ensure an airtight seal.
You can germinate a few of the seeds after drying to test if they are viable. Leave these seeds out for a couple of days, place them on a wet paper towel in a container and leave them for a week. Then they should be wet enough to germinate properly.
If you need to dry your seeds at room temperature, you can use a home garden kit—Regenerations Botanical Gardens offers such a kit. Some people also use various household dessicants or baked rice, though you need 5–10 times more rice than dessicant to dry the seeds properly.