The beginning of spring usually sees me sprawled in the middle of the living room floor, with all my ammo boxes, laying out rows and rows of seed packets sorted by vegetable, and then by variety. Some are even color-coded… and I suddenly realize I have a rather strange obsession with collecting 12 different types of purple tomatoes (and counting).
Inevitably, a handful of seed packets get tossed in the compost pile as I double-check the dates… peppers from 2012, onions from four years ago. Yikes.
Some seeds I’ve only sown once or twice but still have half a packet left, some I’ve saved… and saved… and saved… because they’re so easy to save by the bagful every year (I’m looking at you, beans).
Others are rotated every few seasons as I try new varieties, and by the time I make it back to those Parisienne carrots, it’s already been a couple years. Are they still good? Should I get new ones? How long do seeds really last, anyway?
I’ve combed through countless seed sites and extension sites over the years, wondering this very question. And there seems to be no consensus, especially when you take into account the environment the seeds were stored in, the quality of the original crop the seeds were harvested from, and even the condition of the seeds themselves, as treated seeds will have a different lifespan than seeds in their natural state.
Seeds have a shelf life (as all living things do), and depending on where your particular shelf is, the viability of your seeds can vary by as much as a year or two. When someone asks, “How long do broccoli seeds last?” a safe answer is three years, but in ideal conditions your seeds could still actually sprout after five.
So, you see where our dilemma lies.
What are “ideal” conditions?
In a perfect world, we’d all have second refrigerators with perfectly controlled humidity levels in which to store our seeds. Our seeds would live in this cool, dark, dry environment and 10 years later, those very first tomato seeds we’d ever bought would still be viable.
In reality, our homes go from hot to cold at the turn of the seasons, we sometimes forget our seed packets outside overnight (or at least I do), and an old shoebox will have to do for storage. We can’t really fault ourselves either; who knows what the seed went through before it even reached the store.
Seeds store best below 40°F with less than 10 percent humidity, tucked inside airtight containers in a dark environment.
Every time a seed experiences less than ideal conditions, it suffers a decline in quality. It may not die right away, but it might take a little longer to germinate. Eventually, it will fail to germinate at all.
Using the baggie method with coffee filters (or paper towels) is a good way to test seed germination. By taking a sample of 10 to 20 seeds and pre-sprouting them in baggies, you can gauge how viable those seeds are before committing to potting or planting them. Less than 50 percent germination rate means it’s time to buy new seeds.
Then, there is the issue of seed vigor.
According to Oregon State University, vigor is the “ability of those seeds to produce normal seedlings under less than optimum or adverse growing conditions similar to those which may occur in the field.” That is, the ability of your plants to survive in the ground outside with all the elements working against them, as opposed to being coddled inside in a cozy baggie.
A bean seedling that sprouted within days of being sowed. The cotyledons clearly look healthy and vibrant.
While a germination test can predict viability, it can’t truly predict vigor: how well a seedling will grow in terms of health, strength, uniformity, and root system, not to mention its production of flowers and fruits. A seedling with compromised vigor may have a missing cotyledon, look stunted or scrawny, or seem overall slower to develop than seedlings from fresher seeds.
A bean seedling (sprouted from a three-year-old seed) with missing cotyledons. This seedling will never develop into a normal productive plant.
Try as they might, sometimes older seeds just don’t have it in them to go all the way to seed again. A will to germinate does not equal an ability to thrive.
Image: Oregon State University.
How long do seeds last?
The cheat sheet below takes the average life expectancy of seeds from a variety of sources, including the cooperative extensions of Oregon State University, Colorado State University, Purdue University, and Virginia State University. Consider it more as a guideline, as the longevity of your seeds ultimately depends on the date on the packet and how carefully you’ve stored them since then.
|Brussels sprouts||4 years|
|Corn (sweet)||2 years|
|Oriental greens||3 years|
|Squash (summer and winter)||4 years|
|Herbs and Flowers||Shelf Life|
|Annual flowers||1 to 3 years|
|Perennial flowers||2 to 4 years|