Q: I have leftover seeds from last year and prior years; should I throw them out? I wonder if any of them are viable and will germinate and grow?

A: If you have some seed left from past gardening seasons, you may not have to buy new this year. Reflect upon the storage conditions, inspect the seed, and run a germination test to check the seed viability. You may end up having extra money in your gardening budget to buy additional seeds.

Seeds, according to their habits in the wild and moisture content, have differing life spans. Some, especially fleshy seeds, die very quickly so need to be sown as soon as they ripen; others, particularly seeds, such as those of beans or tomatoes, can be kept for up to ten years.

Most seeds stored in a cool [below 39 degrees], dry place will still be viable for five years or more. Even after that you can plant the old seeds successfully by simply sowing a bit more thickly. Plump, healthy seeds produce the most vigorous new plants.

Seed saving is an easy way to grow your favorite plants from year to year and save money. Use the “ragdoll test”, a simple method to find out how well your seeds will germinate, and know approximately how many seeds you should plant to get the total seedlings you need.

You can check the germination of old seeds (vegetable, herb, flower) by using the “ragdoll test”.

Here’s how in 8 simple steps:
1. Count out a number of seeds and place them on a paper towel. The more you use the more accurate your results; test at least 20 seeds [ideally 50 or 100].
2. Fold the paper towel so that the seeds won’t fall out.
3. Moisten it.
4. Squeeze out any excess water.
5. Place it in a jar or plastic bag to keep towel moistened.
6. Place on a warm windowsill or a warm place that is 70-80 degrees.
7. Label each roll with name and date.
8. After a week, remove and unfold the towel and count how many seeds germinate.

How long will vegetable seeds last if stored properly? Here are some examples of approximate longevity of vegetable seeds.
1 year – Onions; 2 years – Corn; 3 years – Asparagus, Beans, Carrots, Peas; 4 years – Beets, Peppers, Pumpkins, Squash, Tomatoes, Watermelon; 5 years – Broccoli, Cabbage, Cucumbers, Lettuce, Muskmelons.

Any shelf life estimate is approximate and assumes cool, dry home storage conditions. Seed viability decreases over time and under poor storage conditions, so expect reduced germination of old seeds compared to fresh seeds. You may need to plant more seeds than usual to yield the desired number of plants. Use your test results as a guide. Divide the number of seeds germinated by the number of seeds tested to find out your germination percentage. For example, if only half of your test seeds germinate, you now know to take that into account at planting time and plant twice as many as usual. If very few of the seeds germinate in the test, you should probably buy fresh seed.

Perennial Flower Gardener Alert: Stratification of Perennial Seeds

Caution flower gardeners. The above test works well with annual flower seeds and with vegetable seeds. The test is not as useful with perennial seeds because many perennial seeds require stratification before they will germinate.

Contributed by Nadine Salmons, Certified Colorado Gardener

Review CSU Fact sheets 7.221, 7.409, and 7.602 for more information.