Starting Seedlings: How to Test Germination Rates

Have you been hanging on to some seed packets for several years? Or, have you made any semi-questionable seed purchases at the dollar store (I'm guilty of that). If so, you should probably check the germination rates on your seeds. There's nothing worse than sowing a whole row of seeds in your garden, or a whole tray of seedlings in your greenhouse, and having low (or no) germination. Sometimes I get zero germination with seeds I have collected from my own garden. Usually this means the seeds are not viable (for example, gourd seeds will not germinate if they get frozen out in the garden before they are fully mature).

Get yourself a roll or paper towel, and some sandwich bags. Cut a section of paper towel (fairly small, you don't need an entire sheet for each seed variety) and get it wet. Lay out 10 to 20 seeds of one variety in a line (don't go crazy getting them perfect). Fold over the paper towel, so the seeds are covered and in contact with the moist surface. Put the seed/paper package in a plastic bag and label with the variety, date, and number of seeds. Put the bag in a warm spot, but out of direct sunlight (you don't want to cook the seeds).

Tomato seeds on moistened paper towel

Bag it and tag it!

Start checking the seeds after 3 or so days. Germination may take a couple days to a couple weeks, so be patient. Most of your seeds will germinate within a day or two of each other. Once this flush of germination is over, count the total number of seeds that germinated. Divide this by the total number of seeds to get your germination percentage. For example, if 17 out of 20 seeds germinated, you germination percentage is 85%.

I would consider a germination percentage of 80% or higher to be sufficient (90% or higher is even better). However, acceptable germ % can be lower for plants that are known for low germination (like certain gourds, parsnips, and some flowers).