<img height="1" width="1" style="display:none" src="https://www.facebook.com/tr?id=915327909015523&amp;ev=PageView&amp;noscript=1" target="_blank"> Skip to main content
You have permission to edit this article.

Stop squandering seeds! Before tossing out last year's leftovers, test them to see if they'll still germinate

seeds in a packet

Test leftover seeds to see how they will perform in a container or the garden.

I am the despair of my thrifty wife. Each year I place huge orders for flower and vegetable seeds, orders based as much on dreams and aspirations as on actual need. I can see in my mind’s eye the way the garden could be, and order accordingly, ignoring the small internal voice that’s asking me if I will really have time to plant all those seeds.

Of course, I find over the subsequent months that in fact I don’t have the time to plant all of the dozens of packets I purchased. Many languish in the refrigerator, never getting into the soil before winter rolls around and I get ready to place new year’s orders. That’s when my wife suggests we recycle some of the seeds we already have on hand. In the past, I’ve resisted, pointing out that we can’t know if the seeds are still viable, if they will still sprout satisfactorily if planted. In fact, that’s not true, according to Michael Ruggiero.

Are those plants really native to the ecotype you live in?

The former senior curator at The New York Botanical Garden, Ruggiero has been mentoring me since I was a student horticulturist at NYBG back in the 1970s and he was the native plants gardener. He subsequently rotated through almost all the departments at the Botanical Garden, mastering the skills of each before moving on to the next. He’s retired now, but still teaches classes to the students and to the public, including an introduction to plant propagation.

Ruggiero recently recommended to me that I test leftover seeds to see how they will perform in the pot or the garden. To do this, he instructed me to spread 10 seeds from each packet on a separate moist paper towel. Then roll the paper towel up and seal each one in a separate zip-lock plastic bag with a label identifying the type of seed. Store the bag in a warm spot (around 70 F.) out of the sunlight. In two to three days unroll each paper towel and check to see if the seeds have sprouted. If not, roll up the paper towel again, re-moisten it if it is drying out, reseal it in its plastic bag, return it to its warm spot and check again the next day. Repeat as necessary.

When the seeds do sprout, Ruggiero pointed out, you will have learned two things. First, the number that sprout, when divided by 10, will give you a fair idea of the percentage that will germinate when you plant them later in the spring. The second thing you will have learned is how quickly the seeds will germinate. This, according to Mike, is often quite different from the interval indicated on the seed packet.

In support of Ruggiero’s recommendations, I found a useful online article about the typical lifespan of different kinds of vegetable seeds. You’ll find this, “Life Expectancy of Vegetable Seeds” by James Romer, of Iowa State University, at hortnews.extension.iastate.edu/1999/4-2-1999/veggielife.html. This reveals that something as seemingly insubstantial as a lettuce seed will typically germinate even after six years of storage, while a tomato seed will likely still be viable after five. Some seeds are less long-lasting: onions and leeks, for example, stay viable only a year, according to Romer.

Crucial to longevity is that the seeds must be stored under what Romer calls “favorable conditions.” This means cool and dry. Essentially, I (and you, too) should be storing unused seed packets in a jar with an air-tight lid, and to keep the seeds dry, you should add an envelope with a couple of tablespoons of powdered milk to the jar before you cap it. Once sealed, keep the jar in the refrigerator until you are ready to plant the seeds.

A haiku a day can help you get in touch with your garden

With all of this good advice, I’ll be ordering fewer new seeds this year, but planting as many or (who knows?) more. A seed, after all, is a miracle, a promise of new life. It’s certainly nothing to be squandered.

Thomas Christopher is a volunteer at Berkshire Botanical Garden and is the author or co-author of more than a dozen books. He is the 2021 Garden Club of America’s National Medalist for Literature. His companion broadcast to this column, Growing Greener, streams on WESUFM.org, Pacifica Radio and NPR and is available at his website, thomaschristophergardens.com/podcast.

Get up-to-the-minute news sent straight to your device.