It’s that time! While winter slooooowly leaves us here at Maggie’s Farm, we’ve been seeding in the greenhouse each week since early March. Maybe you’re thrifty like me and you like the idea of using up all the leftover seed from last year (Side note: Check out previous post on garden planning to figure out how much seed you’ll need). If that’s you, I’d recommend doing a seed germination test before planting. This is especially important when you’re using older seeds and you are not quite sure what the germination rate might be.
As we’ve learned in class, there can be a significant difference in the germination of seeds after storage. According to “Growing Garden Seeds,” an onion seed stored with no special storage conditions (like a cool and dry environment) might not even be viable the very next year that you want to plant it. Meanwhile, a radish seed may last up to two years and a cantaloupe seed may even last up to three or four years. Of course, if you maintain a cool and dry storage area, pretty much all of the seeds will be viable for much longer.
A germination test helps you determine how to best use your old seed. By knowing the previous germination rate when the seed was purchased, you can then do a test to determine the new germination rate, and therefore have more information about how to best plant the seeds in your garden. It would be such a shame to plan out your beautiful garden and then end up with holes in the rows where seeds never even germinated. By doing this very simple test, you can adapt your seeding rate based on the outcome of the germination test.
You’ll want to do a separate germination test for each type of seed that you’re unsure of. Here’s info about a germination test that I did on Jacob’s Cattle Bean seeds:
Start with a double layer of paper towels and divide it up into four quadrants. Ensure that the paper towels are quite damp; they should be well saturated but not dripping wet. If you have a lot of seeds to work with, count out 100 seeds to ensure a good sample size as I did for this test. If you don’t have that much leftover seed, choose an appropriate amount based on the quantity you have. If you only have 50 seeds to begin with, maybe just choose 15 or 20 seeds.
Next, place the seeds in a single layer divided up into each of the four quadrants, with equal numbers in each section to make them easier to count (in this photo there are 25 seeds in each quarter).
Cover seeds with two more equally saturated paper towels and carefully and gently roll up the whole thing like a burrito to make it easier to slide into the plastic bag where you will then spread it back out.
Label each plastic bag with the name of the seed, the old germination rate percentage (look on the seed packet/bag for this information), and the date of your germination test. Carefully place your paper towel seed burrito into the plastic bag and unroll it so it is flat.
Get as much air out of the bag as possible. You should place the bag(s) in a fairly warm space, but you can leave them stacked on top of one another, as most seeds do not require light to germinate. We stored ours in a cardboard tray in our office space so they could be warm but out of our way.
Keep an eye on your seeds; they will likely need about a week to germinate depending on how warm it is, although some might need more/less time. I checked on these Jacob’s Cattle Beans exactly one week later and found that due to how big these seeds are and how much water they absorbed, the paper towels had dried out. There were no signs of germination but the outside of the seed was wrinkly from absorbing all the water. I decided to re-moisten both the top and bottom paper towels and to give them a bit more time.
Three days later, and 10 days since I began the test, the seeds started to germinate. I did a quick count to get an idea of the rate at this point and determined the germination rate was about 80% for this three year old seed. Not bad!
Just for the sake of experimentation, I let the seeds go a bit longer just to see if the rest would germinate. Typically a seed company would have guidelines they were following very closely—creating certain standards of temperature, moisture, and length of time as parameters for their test. But it was easy for me to just allow them a few more days to see what would happen.
By giving the seeds a couple more days, I was able to see about a 92% germination rate! Again, it’s not that I somehow improved the germination rate by keeping this old seed, but more so it’s likely that the seed company’s test was looking for a certain percentage of germination within a certain number of days.
The takeaway—my Jacob’s cattle bean seed is still good to go! I can pretty safely expect an 80% germination within about a week if conditions are right, and it might even be better than that with a bit more time. I would not need to change the sowing rate when planting and would just follow what is on the packet as far as how thickly I can sow these seeds.
However, some of the other seeds in our germination tests were less than ideal and would greatly affect the seed sowing rate. If you test a seed from 2014 and the old germination rate on the packet was 92%, and now there is only 60% germination, you would likely want to sow the seeds more thickly than the package suggests.
Happy Germinating! ~Amber
Source: Johnston, R., Jr. (1983). Growing Garden Seeds: A Manual for Gardeners and Small Farmers. Albion, ME: Johnny’s Selected Seeds.