how fresh are leftover seeds? viability, and vigor
THE SEED CATALOGS are here, and I’m getting organized. Step 1: taking inventory of what’s on hand. But how many of the seeds I have left over are still not just viable, but also have sufficient vigor to perform well start to finish?
That’s the sort of “advanced” question I’m wondering about now, after a little episode with a packet of leftover collard seeds that I was feeling so smug about—a feeling that quickly changed to dismay a couple of weeks into their sorry time outdoors.
When taking inventory, first I refer to the general guidelines for how long seeds last, summarized generally in the chart above, and detailed in this article on estimating seed viability. I always suggest a germination test of any packets older than about a year (assuming there are enough seeds left for one).
The collards in question, which were in their third year with me, sailed right through; virtually all of them germinated. But in the ground, things were different: They came up, yes, but then just stood there, like miniatures, never developing.
Germination tests predict viability (the ability to germinate), but they don’t accurately predict vigor—the seeds’ potential for uniform, fast germination and subsequent development in outdoor conditions, not the cozier, controlled conditions of a germination test. Life in the field isn’t the same as life wrapped in a piece of paper toweling in a plastic bag indoors on the kitchen counter, or in the special refrigerator unit of a seed-company testing lab (above).
“Seed vigor is a measure of the extent of damage that accumulates as viability declines,” says part of a class curriculum on seed biology at Ohio State University. “Eventually the seed dies, but first vigor declines gradually.”
Like my unfortunate collards.
If I’d had a second packet of fresher collards seeds on hand, and tested it at the same time as the three-year one, I might have seen some differences (emphasis on might, since I am not trained). Perhaps the roots of the older seed would have been less developed, even stubby or non-existent, or the cotyledon (first leaves) might have been in some way visibly deformed, perhaps with one missing, or over all the tiny plants on that paper towel might have looked more crooked or scrawnier than those from the fresher lot.
Maybe like the examples from the Oregon State University seed laboratory bulletin on the importance of vigor testing in agriculture.
There’s no home test for vigor (there are several kinds used in agriculture, where the subject is the focus of continuing fine-tuning). But knowing a little more than I did about vigor when I failed with those deceptively high-germinating collards serves several purposes for me, and that’s why I mention it now.
It makes me think about storing my seed more carefully, and about replacing seed more frequently rather than pushing it. Also—small comfort, but something at least—it makes me realize that last summer’s collard failure wasn’t something I did wrong in the planting or aftercare. Try as they might, those seeds just didn’t have it in them to go all the way to harvest.
Remember: The chart up top of viability in years assumes that you’re storing seed in optimal cool, dry conditions. And also remember: The seed company you bought it from might have stored it for one or more of those years already!
I’m now clear: Just because seed germinates, doesn’t mean that it will thrive.
- read my more in-depth seed viability article, with extra links to explore