Most gardeners end up with boxes of unused garden seed. Sometimes they are leftover from previous years and sometimes they were given to them. I’ve dealt with old seed from both scenarios. Years ago my wife’s grandparents gave me the last seed of a corn their ancestors carried from Ohio to Southern Illinois, by ox cart, in the 1800s. Their family had grown it, from generation to generation, until their generation. They stopped planting it 15 years before giving me the seed. Grandma pulled the sack out of of a chest which smelled of moth balls. It felt like I was in a dream when she handed it to me I couldn’t believe this gift, yet, when I tried to grow it, not a single seed germinated. These days I find packets of seed I misplaced a couple years ago and have to decide what to do with each one.
So, what should one do with old seed?
The first thing to do, if possible, is to determine the age of the seed. Generally, if the seed is in a commercial seed packet, one will find a date on the packet.
This is a very precise label. It means that the seed company packaged the seed with the expectation that it be used in 2012. That seed certainly did not come off the plant in 2012. It may have been produced in 2011 or it may have been produced earlier than that. Still, when a seed packet says that it’s packed for a given year, the customer can safely assume that seed should have a good germination rate if used that year. Most seed companies test their seeds’ germination rates before packaging. I just pulled the packet pictured above out of a box, and it has seed. Should I use it? This brings us to the next recommended step.
Determine the average viability of the garden seed.
“Average viability” means the average time that seed, stored in a cool dry place will remain usable, or in other words how long it will have an acceptable percentage rate of germination. Some seed within the batch may last several years longer than the average, but at some point the germination rate will be so poor that it is hardly worth planting. This is especially true if it’s being grown to produce food. Different species of plants’ seed stay viable for different amounts of time. Lettuce, for instance, is only good for about two years in storage, but squash and pumpkin may last 8 years. Beans and peas are generally good for about 4 years, and after that, their germination rate plummets.
Iowa State University Extension Life Expectancy of Vegetable Seeds
There is some variation in predicted viability among sources I’ve checked, but the differences can be accounted for by variations in atmospheric humidity and the meaning of “room temperature.” Here’s a link to a story which illustrates why one might go through the trouble to grow old seed: To Make An Heirloom: Story of Calico Willow Leaf Pole Lima.
Decide whether or not to use the old garden seed.
If the seed is well past the average viability and is easy enough to obtain, it’s probably best not to waste time and resources to use it. If one were simply to go out to the garden at the appropriate planting time, and plant this seed, they would then have to wait a week or ten days in order to know if it grows, and if so, if enough of it grows to make the planting worthwhile. In many cases, I’d just rather get new seed in a timely manner and go with it. But if there may be other factors which make growing the seed worth trying. Perhaps it may be borderline old and you wonder if it will grow or not. If so, why not do a germination test? Know beforehand whether it’s going to work.
How to do a basic germination test:
- Take a couple sheets of paper towel and fold them like a handkerchief.
- Wet the towels and squeeze them out until they no longer drip.
- Unfold them enough to make a place to put some seed.
- Put some seed on the damp towels and fold them into it, to keep them consistently damp.
- Place the seeds, in their towels, into a plastic bag, leaving it slightly open, to allow some ventilation.
- Place everything in a warm location (80-90 F.) and wait a few days before checking.
- Check on the seed for several weeks, keeping notes on how many germinate (send out roots).
By doing a germination test, one can count the seeds which germinate and divide that number by the number that were originally placed on the damp towels, multiplying by 100. This will give you the rate of germination. For example, if you place 25 seeds on the damp towels and five germinate. Divide 5 by 25 and multiply by 100. This gives a 20% germination rate.
What if the old seed is possibly the last of its kind?
As a seed saver, I don’t know how many times I have held “the last of its kind” being 10 to 20 years old or older. It is heartbreaking to see a piece of living history at “the end of the line.” There are some somewhat extreme measures which can be taken to germinate such seed (sometimes, not always). Some seed can retain a spark of life, albeit without the strength to fully germinate, for a long long time, in rare cases, for thousands of years. Should you be desperate to germinate some old seed, here are some possible techniques.
- Soak the seed for 15 minutes to an hour in a .15% hydrogen peroxide solution, before placing in growing medium (1 part grocery store peroxide to 20 parts water). This helps eliminate fungus spores which are likely to be harbored in the seed’s case.
- Place the seed, very shallowly in sterilized growing medium treated with a plant vitamin/fertilizer treatment. The product I have most heard about is called Superthrive. Here, also is a link to a post by a person who is really into growing old cannabis seed. The technique would work for for most garden vegetable seed.
- Keep the freshly planted seed tray under a grow light. Be sure the seed is so shallowly planted, that the light can reach it. This way, if a seed so much as cracks open, it can immediately start gaining strength from the light.
- Keep the old seed, in its tray on a heat pad set at 80-90 F. For most garden seeds, such as tomatoes, beans, corn or squash are benefited by the warmth.
- Cover the tray with plastic wrap to avoid drying out and contamination by airborne spores. Remove the plastic when/if seeds come up.
Such a techniques are laborious and can be costly. They are worth it if the seed is extremely rare, but you can obtain the same variety, fresh, today, it would be very much better to get new seed.