Mary's Veggie Garden

March 3, 2011

Will My Seed Grow? Germination Testing

Filed under: Beets,Carrots,Gardening,Parsnips,Seeds,Vegetables — marysveggiegarden @ 9:11 am

In January, it’s fun to curl up under a cozy quilt and browse the seed catalogs. While snow falls outside, I dream of my next garden. Of course there is also the practical part: sorting through my seeds, tossing out the nearly empty packets, and making a list of varieties to purchase. I always have several packets with plenty of seed even though I planted the seed for the past year or two so I must figure out whether the seed will germinate another year.

Results of 12/2011 cucumber seed germination test. Seed on the left, from 2008 is no longer vigorous and will be discarded.

Several times other gardeners have asked me the question, “If I plant this old seed, will it grow?” My usual answer is, “ I don’t know. It depends on the variety, and the conditions where it was stored. Some seeds, like parsnip, are good for a single year, others, such as basil, may sprout after 5 or 6 years.”

You can get a definite answer to the question “Will my old seed grow?’’ by germinating a few seeds indoors. If it grows during the test, it will grow later, given the proper planting conditions.

The test:

  • Remove some seeds from the packet to test. If the seed is tiny, and there is a lot in the packet, take 10 or even 20 seeds. For very large seeds, 5 is enough.
  • Take a small piece of paper towel, a quarter or half sheet. Using a pencil, label one edge with the variety and number of seeds
  • On a separate sheet of paper, write the variety, seed year, number of seeds, and the start date of the test.
  • Moisten the paper towel, place the seed on one half, then fold in quarters to cover the seed.
  • Place the damp, folded towel in a small plastic bag and put it someplace warm, where it won’t be forgotten. I put mine on top of the micro-wave.
  • After 4 days check for tiny sprouts which look like short white threads curling from the ends of seeds. Check every day thereafter. Most seed of a given variety will germinate within a 48 hour period, although older seed may take 6 or 7 days to start germinating and continue for 3 or 4 days.
  • If the test seed has not started growing within two weeks, stop the test, and throw the seed packet into the trash.
  • If the seed germinates, count the number of sprouted seeds and figure the percentage. This is the germination rate. Then discard your sprouted seeds.

Note: some flower seeds need light to germinate. The packet will have that information. If light is needed, put the towel in the bag without folding it over the seeds, then keep it in a well lighted place during the day.

Once you know the germination rate, you can decide whether or not to plant the remaining seed. If 80% or more sprouted, it is safe to plant. Seed with a germination rate of less than 80% can be planted more thickly, and seedlings can be transplanted to fill gaps. I tend to trash anything with a germination rate of 50% or less, unless it was very expensive seed, then I’m more willing to fuss with it. Here are the results of my testing in January 2010:

Variety Seed Date, from packet Number of seeds tested Germination, day 5 Day 7 Day 8 Day 9 Day 10 Verdict
Beets, Lutz 2007 10 0 10/10 100% Plant in 2010
Parsnips, Hollow Crown 2009 20 0 1/20, 5% 2/20, 10% 4/20, 20% no change Buy fresh seed
Carrots, Ingot 2007 20 0 9/20, 45% 12/20, 60% 15/20,75% no change Plant thickly

The Cornell Growing Guides at how long most vegetable and some flower seed can be saved. Click on the plant type, then scroll to the “Growing Information” topic, section “How to Plant”.

VarietyTest Dec. 2011 Seed Date, from packet Number of seeds tested Germination, day 6 Verdict
Cucumber Marketmore 2009 10 8 Plant in 2012 very vigorous
Cucumber Straight 8 2008 10 8,but not vigorous, barely sprouted Discard seed
Soy Shirofumi 2011 7 6 OK
Peas Cascadia 2010 5 5 OK

Soy seed left, Cascadia Snap peas right, sprouted for germination test.

The freshly germinated cucumber seed smells wonderful!

For the soy test I deliberately tested the smallest, ugliest seeds in the envelope figuring if those grew, the rest will be OK.

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