Sow these seeds or throw them out?

Should I sow seeds that were a left-over from last season, or is it best to discard left-overs and always use new seed? This blog post may help you make up your mind.

 

For the most common vegetables I found ....

In short:

• Onion, Parsley and Parsnip seeds stay alive for less than a year
  
• Most other vegetable seeds remain viable for around three years
• Cucumber, Celery, Lettuce, Radish, Tomato and Turnip remain viable for five years or more.
  

This information came from ....

These estimates came from ten seed growers, seed merchants, university researchers and home gardeners who were confident enough to put their viability-estimates on the internet. I also took into account my own experiences over a 30+ year period of food gardening. It turned out that the estimates by all these people were often quite similar, and that is what the table above represents. You will find my list of sources at the end of this blog post.

These estimates will be correct if ....

These estimates will be correct if the seeds were treated well from the moment they were harvested until the moment you put them in the ground.

The best storage method, for instance, is in above-zero but below-10 degree Celsius temperatures, in low or no light, in stable low humidity. Sealed packets in airtight jars or containers, with a sachet of silica or dried rice in each container, in a fridge, is ideal!

But don't forget to take into account where seeds were before they were yours. If once, not so long ago, they were displayed in a shop or nursery, then, if they were in a light bright spot that wasn't cool, then they may not be worth buying!

Always check Best Before dates on packets and don't buy seeds if there is no date. These Best Before dates sometimes are a too-cautious attempt by the seed merchant to predict viability. I found that seeds are often still viable past that date.

If you yourself harvest seed from your garden, always write the date of harvest on your seed packet. You count the sseds' Best Before date from the time of harvest.  This blog post may help you determine those dates.

Checking and testing seed 

You can get an idea of how viable your seeds are in the following ways: 

• A visual inspection - A basic assessment to differentiate healthy, plump (viable) seeds from seeds that are shriveled, affected by insects, or immature (green or pale). 

• A float test - Determines if a seed is full or empty. Empty seeds will float.  After this test make sure to thoroughly dry the seeds (not in the sun) or plant them immediately.  This method may not work for tiny very light seeds.

Most of these seeds have passed the float-test

• A cut test - Determine the internal state of a few seeds you are willing to sacrifice. Are they full, shriveled or empty? Again, this method may not work for tiny seeds.

• A seed-viability test - You need a sealable plastic sandwich bag, paper towels and a sunny window. Now do the following:

1. Moisten the paper towel enough so seeds will receive moisture at all times. 
2. Fold 10 seeds into the towel (10 seeds makes it easy to determine germination percentage. If 8 seeds sprout, you have 80 percent viability). 
3. Seal the seed-filled paper towel in the bag and then mark the bag to identify the seeds. 
4. Place the bag in a location where the temperature is around 20 degrees Celsius. 
5. Wait 7-14 days (even for slowly germinating varieties there should be some change by then). 
6. Be sure the paper towel or filter does not dry out during this time. 
7. Count the number of seeds that germinate and calculate the percentage. If less than 70%, you could still use these seeds, but you would sow a lot thicker. 

With some seeds (peas for instance), if you carefully sow the seeds at the end of the test, they will continue to germinate, and you have not lost any time doing the test. 

There is of course no guarantee that a seed that germinates will grow into a healthy plant. If only 20% of seeds in your test germinate, the ones that do, may be weak and plants may not reach maturity. 

What to do with seeds that you decide are past it?

Save them up, mix them all together and sow them somewhere in your garden as a green manure. What is a green manure? - see Food Garden Group blog post Why Green Manure?.  It will be an interesting thing to do because you will find out which seeds were actually not past it, and that will help you become better at determining which seeds to throw out next time.  

A green manure mix of Past Best Before seeds

 

Autumn is often the time of year that I have a few months between crops, an ideal time to sow expired seeds that might give me some green manure. This season I sowed a mix not unlike the photo above, and after a fortnight got mostly beans, some peas, and a few other things coming up. Interesting!

There is lots more interesting stuff about seeds ....

You will find more interesting info about seeds in blog post The Life Expectancy of Seeds on the Food Garden Group blog. It discusses the oldest seed that ever germinated, reasons why seeds may not germinate, sow by dates on seed packets, and what seeds I use. 

 

Happy sowing!

Max Bee

Where most of my info came from:

• The Seed Collection
• Seed Collecting Guide by Stefan Mater
• A seed viability chart at High Mowing Seeds
• Seed Viability on a page of Iowa State University 
• How long do seeds last by four sources at A Way To Garden
• Seed Viability Times at Reading Food Growing Network 
• Knott's Handbook for Vegetable Growers