Does Freezing Kill Seeds? – Information On Using Seeds That Are Frozen
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.
Does Freezing Kill Seeds?
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.
Using Seeds that are Frozen
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.
How to store grass seed over the winter to use in spring
Did you know that the viability of grass seeds depends greatly on the storage conditions? When seeds aren’t stored properly, they will fail to germinate when your turf is ready for spring lawn care services. Seeds that are stored well can be used the following spring in Calgary with your seasonal lawn maintenance.
Generally speaking, seeds that are stored in cool, dry conditions over the winter maintain viability the longest. If you’re storing grass seeds to use in spring, be sure to follow this guide to maintain their viability.
Storing grass seeds in winter
Where to store your seeds over the winter
Often, homeowners will store their seeds in a garage or a shed without knowing that this can expose seeds to excess humidity or freezing temperatures. The ideal storage place for your seeds is in an air-tight container placed in a basement or any cool, dry area in your home.
Seed viability relies on a few different factors, including:
- Temperature – The ideal temperature for most seeds is above freezing but under 15 degrees Celsius. In Calgary, where we experience cold winters and hot summers, a garage or shed may not allow seeds to hold their viability for very long.
- Moisture – Too much moisture negatively affects seed viability. Always store your seeds in an air-tight container or plastic bag so that they cannot absorb moisture. In general, the cooler and dryer the storage area is, the longer your seeds will remain viable.
- Humidity – Seed viability declines rapidly when exposed to humid climates, further highlighting the importance of storing seeds in an area that is cool and dry.
How to know if your seeds are still viable
Some seeds can last for several years, while others have a short life. When properly stored, the seed’s shelf life can be extended. Come springtime, you can do a couple of tests to check if your seeds are still viable.
The water test
Put your seed in a container of water and let sit for 15 minutes. If the seeds are viable, they will sink. Seeds that float will likely not sprout.
The germination test
We recommend waiting to do this test closer to the time of planting, so any seeds that sprout can be placed into your garden immediately. To do the germination test:
- Take your seeds and place them in a row on top of a damp paper towel.
- Fold the paper towel and seal it in a zip-up plastic bag.
- Place this plastic bag in a warm location away from direct sunlight, ideally on top of the refrigerator.
- Check once a day and carefully mist the paper towel with water if it requires more moisture, being careful not to overwater.
Your seeds should sprout in a few days, depending on the specific germination time of your seed species.
How long does grass seed viability last?
Grass seeds last between 10-18 months from the testing date when stored under ideal conditions. Keep in mind that every seed is different, and results vary. With proper lawn care services and seasonal maintenance in Calgary, your grass seeds can sprout and help your garden thrive.