We buy a LOT of seeds around here. Of course, that’s because we grow a lot of stuff. We do buy many of our seeds in bulk to save some money but don’t always plant all of it by the end of the season. So, when those seed catalogs start rolling in at the beginning of the year I do an inventory of what’s left from the previous year before ordering anything. Sometimes I come across seeds in my stash from two or more seasons ago – varieties we didn’t use again right away or a veggie we skipped a year planting. Thankfully most seeds, if stored properly, will last several seasons. But their germination rate does drop over time and that’s important to know, especially if you’ve only got space for a few plants in your garden. Before deciding whether to include seeds as part of my inventory, or toss them and order new ones, I do a germination test. If you’ve got seeds laying around and you’re not sure whether to toss or keep, here’s some help.
Basic Seed Germination Test
What you’ll need:
How to test:
1. Tear a paper towel in half and moisten it with water. I soak it down, then squeeze most of the extra out. It needs to be moist but not dripping.
2. Fold the paper towel in half and lay flat on your work surface.
3. Count 10 seeds from the variety you’re testing. Spread those seeds out on one half of the paper towel so that they’re not touching.
4. Fold the paper towel over on top of the seeds and press down lightly, essentially sealing the seeds inside.
5. Mark the variety of seed, the date you started the test, and the number of expected days to germination on the plastic bag.
6. Slide the paper towel with the seeds inside the bag and seal. If using fold-over sandwich bags, just fold it under itself to keep the towel from drying out too quickly
7. Place the bag in a warm place out of direct sun. If you keep your house cool, like we do, use a seedling starter mat or heating pad to help. Be sure to put a couple layers of towels between the seeds and the heat source or you risk overheating the seeds and hindering sprouting (essentially cooking the seeds).
8. Check the bag every couple of days to be sure the towel stays moist. Spray the towel with water if it gets dry before sprouting.
Check your results
Once the expected days for germination have passed, count the number of seeds that sprouted. This will give you your germination rate. If 8 seeds sprouted you have a germination rate of 80%, which is good. Anything less than 60% is sketchy.
Generally if my germination rate is 50% or 60%, I’ll use the seeds but plant them more thickly than I would if they were germinating better. 70% or higher germination rate, I will plant as usual.
What you’re comfortable planting will depend on how much space you have and the number of seeds leftover. If you’ve got enough room and enough seeds to over plant, then go for it. But if you’ve got limited space and need what you plant to germinate with some assurances, you may only want to keep seeds that germinate at 80% or better and replace those that don’t. Either way, doing a simple germination test before placing your seed order may save you money and prevent more seeds from sitting around waiting to go in the ground next year. Happy planting!