By: Darcy Larum, Landscape Designer
If you have ever read the labels on seed packets, you’ve probably noticed their recommendations to store unused seeds in a cool, dry place. These instructions are a little vague. While your garage, garden shed or basement may stay cool, they can also be humid and damp during certain times of the year. You may wonder how cool is too cool, and whether freezing kills seeds. Continue reading to learn more about storing seeds in the freezer and properly using seeds that are frozen.
Seed banks store rare, exotic and heirloom seeds in refrigeration units or cryogenic chambers to ensure the survival and future of specific plant varieties. As a home gardener, you probably don’t have a cryogenic chamber in your garden shed, and you also probably don’t need to store thousands of seeds for decades. That said, the kitchen refrigerator or freezer are sufficient for storing leftover seeds, as long as they are stored properly.
Improper freezing can kill some seeds, but other seeds may be less fussy. In fact, many wildflower, tree and shrub seeds actually require a cold period, or stratification, before they will germinate. In cool climates, plants such as milkweed, Echinacea, ninebark, sycamore, etc. will drop seed in autumn, then lay dormant under snow through winter. In spring rising temperatures and moisture will trigger these seeds to sprout. Without the preceding cold, dormant period, though, seeds like these will not sprout. This period of stratification can easily be simulated in a freezer.
The key to success when freezing seeds is storing dry seeds in an airtight container and keeping consistent cool temperatures. Seeds should be thoroughly dried before being frozen, as the freezing process can cause moist seeds to crack or split. The dry seeds should then be placed in an airtight container to prevent them from absorbing any humidity and taking on any damaging moisture.
Seeds stored in a refrigerator should be placed near the back of the fridge where they will be less exposed to temperature fluctuations from opening and closing the door. Storing seeds in the freezer will provide seeds with more consistent temperatures than refrigerator storage. For every 1% increase in humidity, a seed can lose half its storage life. Likewise, every 10-degree F. (-12 C.) increase in temperature can also cost seeds half their storage life.
Whether you are storing seeds for just a few weeks for succession plantings or to use a year or two from now, there are some steps you must take when using seeds that are frozen.
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A little powdered milk can help you grow your favorite plants again and again.
You've harvested your summer seeds and now it's time to store them to help you get a jump-start on next season — but storing them improperly could make your dreams of a bountiful garden fall flat. Follow our easy guide to storing your saved seeds that will save you time and money and give you your best harvest yet.
This is very interesting. How long were the seeds stored after freeze drying before they were reconstituted and used? I save seeds from the garden every year as well as purchasing seeds. If this process helps them last longer then the normal 2-5 year viability window it would be great to know. Anyone that does actual tests on this please post your details. Thanks
I think this would have a good impact bug/pest wise. No chance of seeds bringing unknown parasites INSIDE!
how long were the freeze cycle and the dry cycle times -thanks
I want to know if the seeds were already dry before putting them in the freeze dryer or if they were pulled from the plant and immediately put into the freeze dryer. i will likely try both ways with my freeze dryer to test it out.
The article said that the seeds need to be normalized first by standard drying techniques and then freeze-dried.
I just wanted to drop a link here for everyone to reference. Someone actually tried getting a patent to do this commercially in 1973, with instructions and results listed on this page. They successfully tried flash-freezing as well as putting the seeds directly in the freeze-dryer. Not necessarily a brand new technique, but still relatively new, and from this patent information, is shown to produce healthier seeds than traditional drying methods. https://www.google.com/patents/US3950892
And, you can have seeds that last 20-30 years!
Thank you for the link Becky! I read it and understood most of it at the “kinda-sorta” level. I think it said that the seeds need to be dried to the normally acceptable level of moisture before being freeze dried? I guess what I am trying to figure out is if I buy heirloom seed packets, and then freeze dried the seeds, when rehydrated thru planting, would they still be viable? Would it help to soak the seeds first or do I just need fresh seeds? Thanks to any and all that can enlighten me!
I am very interested in the idea of freeze drying seeds. I had a giant pumpkin last year that weighed perhaps somewhere on the order of 600 pounds. While this is nowhere near the record for giant pumpkins (2,624.6 pounds in 2016). I wanted to dry my pumpkin seeds. I made a mistake of bagging them to soon and they molded. All ruined. So, this year I am going to freeze dry my giant pumpkin seeds. What would be most helpful for me is info/suggestion on technique. Should I dry them as best I can before freeze drying?. Or, should I simply take the seeds directly from the pumpkin to the freeze drier?. Any suggestions would be greatly appreciated. Thanks very much for any and all suggestions and comments.
Pumpkins make a LOT of seeds. Why don’t you try both methods?
They’ll last longer and taste fresher.
It’s not a bad idea to keep a variety of nuts and seeds on hand. They’re healthy, tasty, and useful for snacking, baking, breading, and enhancing salads. But whether you buy them in bulk bins, in the baking aisle, or online, you shouldn’t store them in your panty. Here’s why.
We all know nuts contain fat. The good news is that it’s primarily the “good” unsaturated fat that’s helpful for lowering cholesterol and keeping your heart healthy. The bad news is that these fats are delicate and can turn rancid when exposed to light, oxygen, and heat—the kind of heat that settles in your cupboards all summer. Moisture can also be a threat in humid climates.
Refrigeration—and better yet, freezing—battles each of these hazards and can slow down the deterioration of the oils so the nuts won’t spoil. As is the case with most foods you keep cold, nuts will also simply last longer at cooler temps: about 6 months in the fridge and about a year (or more!) in the freezer.
Bonus: because of all that oil, nuts are less susceptible to freezer burn. (There are two exceptions: fresh coconuts and chestnuts, which have a higher moisture content and can hold for only about 2 weeks in the fridge and should not be frozen.) Nuts and seeds are also usable right out of the fridge or freezer—no thawing required.
While eating nuts or seeds that have seen better days won’t necessarily make you sick, their assault on your tastebuds will be pronounced. Therefore, it’s also a good idea to transfer nuts into an airtight container—not store them in the bag you brought them home in—because they can pick up lingering odors in your fridge or freezer.
And if shelf life and freshness aren’t reasons enough to store your seeds and nuts in your freezer, consider this: various species of moths, beetles, and weevils love nuts as much as you do and can think of no better place to start their families.
Lest you’re left with that unwholesome image burning in your brain, here’s another tip for preserving nuts: keep them as whole as possible. Once shelled, they can lose up to 50% of their shelf life, and chopped nuts have about half the shelf life of whole, shelled nuts.