How to Test Leftover Seeds

Test seeds that you’ve saved from last season to see if they are worth planting.

Reader Contribution by The Natural Gardening Company
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by Adobe Stock/onamakela.com

Those of us who plant our gardens from seed nearly always have a stockpile of seeds from previous seasons. About this time each year we ask ourselves, “Should I use the seeds I have on hand, or buy new ones?” Tempting as it may be to use last year’s seeds, they are not free. There is a cost in time and effort that comes with planting seeds that fail. At the very least, last year’s seeds can throw you off schedule if they aren’t viable. The simple reality is that you don’t know if your seeds will perform at an acceptable level unless you test them. You can’t tell by looking at them, and you can’t tell by the date on the packet. There are too many variables in the way seeds respond to storage conditions and how long certain varieties remain viable. You need to test.

Testing seeds is easy and inexpensive. All you need are some petri dishes, filter paper, a pair of tweezers and your seeds. A medicine dropper also comes in handy. If you can’t find them locally, petri dishes and filter paper can be ordered online from Indigo Instruments.

In order to get an accurate test you need a sufficient sample of seeds. 25 will do. If you have fewer than 25 seeds, you need to test enough of whatever you have to get a meaningful result, at least 10. You simply put the filter paper in the petri dish, and then place the seeds one by one on the dry paper with your tweezers so they are separated from one another (this makes counting easier later on). Once your seeds are distributed over the paper, carefully drop water in different spots until the moisture spreads throughout the filter paper. You want it moist but not saturated. Too much water will make the seeds rot. Start with a few drops to see how they spread. Add more if the paper is dry.

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