Using Older Seeds

This is the time of the year when thoughts turn to seed saving – at least, that’s the case around here. Veggies are getting ripe, lettuce is bolting under the pressure of the heat and the beans are plumping up their pods. I’ve written a number of blogs about the why of seed-saving and a bit about the how. One thing I haven’t really talked about, however, is seed storage and the use of older seeds.
What are older seeds? Depends on your definition. If you look up the issue of seed saving, you’ll see most sources tell you that seeds are almost never good past five years. In the case of onions, the standard is supposed to be one year. And that’s assuming they’ve been properly stored. Tell that to the onions currently sprouting in my garden from seeds that were at least three years old. Or the summer squash from seeds saved in 2011. These seeds didn’t have any special storage conditions, either. They were in the plastic totes I keep in the bottom of the bedroom closet, which has neither heating nor cooling vents. That means summer temperatures as high as 90°F and winter temps around 60°F.

Seeds have much better potential longevity than people give them credit for. Nita Wilton recently noted in her Throwback at Trapper Creek blog that she had Red Russian Kale seeds sprouting in a recently cleared lawn area. Kale had not been planted there for at least 15 years. Anasazi beans come from seeds reliably dated to be at least 1,500 years old. They were stored in a clay jar sealed with pitch found in the southwestern American desert. And scientists have been able to germinate wheat seeds stored in the Egyptian pyramids. In the latter two cases, a big factor in seed longevity was probably the dry environment.
The basic keys to seed storage are temperature, light and humidity. Makes sense, when you consider that those three factors are what encourage seeds to sprout. Of the three, humidity rules. Once moisture penetrates the seed coat, even if temperatures aren’t ideal, that seed is going to try and sprout. I store my seeds in paper envelopes, sorted into categories in old cardboard shoe boxes, and in plastic totes with locking lids. I scatter desiccant packets throughout the boxes and the closet in which they are stored is not exposed to moisture. Although the light is turned on inside the closet at least once a day, my seeds are well-protected. The ideal temperature is supposed to be between 40 to 50°F. Obviously, I don’t achieve that ideal…

Now that you’ve read this, I suspect you’re going to use those older seeds. If you’ve been growing your own for a while, you usually have a pretty good idea of how many you need to plant. Since you do save your own seeds, you aren’t constrained by the cost. I usually have at least three times as many seeds as I need for this year’s crops, plus enough left over for next year. Plant thickly – if I’m supposed to seed every four inches, I seed every one-and-a-half or two inches. With onions, I pretty much carpet the row; the seeds are usually touching each other. You can do germination testing ahead of time, if you want to be precise, and I often do test just to see what I can expect. But with my plant-them-close method, even if germination is 30%, I should have enough plants to make a crop. Older seeds may take a week or more longer to germinate, so be patient. I note which ones germinated first and looked healthiest at germination. I try to make sure I include seed from those plants when I save for next year.
So, Grasshopper, go forth and sow older seeds. They don’t really have expiration dates.