Keep or Toss? How to Assess if Your Plant Seeds Are Still Viable

It’s hard to order just the right amount of seeds. Maybe you ordered a packet of 25 tomatoes when you only needed a few plants, or perhaps you bought a thousand beans to enjoy the savings that come with bulk pricing. No matter the case, you have access to seeds from previous years.

Planting them means you don’t have to spend money purchasing new ones. However, if you plant seeds with poor germination rates, you’ll end up with a sparse and disappointing garden.

Instead of tossing your whole seed bank and purchasing new ones each year, you can learn how to check if your seeds are still viable. By planting good ones and tossing bad ones, you can save money and enjoy a healthy garden.

Check the Packaging Date

All seed packets should have a pack date that indicates when the seeds were packaged. That’s why saving your seed packet is always a good idea, even if you transfer them to a new bag or container. Also, if you save your seeds, you should always label them with their year of collection.

You can use this date to determine whether your seeds are still viable. Although seed viability decreases as years pass, many vegetable and flower species are worth planting until three years after their pack date. However, the exact time varies by crop.

Consider Storage Conditions

Although you can expect a seed’s viability to match the length I listed above under ideal storage conditions, heat and moisture can decrease the shelf life. So, if you accidentally left your seed packets outside for a few days in the summer or spilled water on them, you can expect diminished viability.

The best storage conditions are cold and dry. Temperatures between 35-40°F (2-4°C) are ideal for most species, so keeping them at a standard household temperature can shorten their lifespan. High humidity can also decrease how viable seeds are, so keeping them in a waterproof bag or container is important.

Are you wondering how storage conditions affect shelf life? Let’s look at an example.

Beans should have good germination rates for about three years. However, if you keep them in your warm office, only 75% may germinate after a year. If you keep them in this warm room for two years, the germination rate may decrease to 50%. Therefore, it’s always a good idea to keep storage conditions in mind when investigating whether you should keep your seeds.

Check for Pelleted Seed

Another factor that impacts a seed’s shelf life is whether or not it’s coated. Most seeds are sold in raw form, but you can also find ones coated in an inert substance that makes them more uniform and easier to handle.

For example, pelleted lettuce and carrots are easier to handle than raw seeds. Their coating also makes them uniform in shape and easy to use in mechanical seeders. That’s why many commercial farmers choose pelleted seed.

However, it’s important to note that pelleted types have a shorter shelf life than raw ones. No matter what type of crop you’re growing, you should use your pelleted seed within a year. If you want to use viable seeds after a year, sow them in an open flat and then move any seedlings to individual cells.

Physical Assessment

Sometimes, seeds will let us know when they won’t germinate. If you notice they are crushed, cracked, or otherwise unusual-looking, it’s unlikely they’ll germinate well. Therefore, it’s best to toss any broken seeds.

If your planting material looks discolored or wrinkled, they may be fine! Since they are stored dry, some wrinkles are natural. However, if you’re unsure, you can always plant a few and see if they germinate.

When In Doubt, Test

If you’re still unsure whether your seeds are viable, conduct a germination test. If you have fewer than ten, you might as well plant them rather than test them. However, if you have a large packet, testing them in January allows you to decide whether you need to order more for the upcoming growing season.

While some people say you can test a seed’s viability based on whether it sinks or floats, this isn’t the most reliable method. Instead, you should conduct a germination test. To begin, select 20 (or more) seeds. The more you test, the more accurate the results.

Dip a paper towel in water and then wring it out until it’s moist but not wet. Set them in a line on the paper towel, then fold the towel over to cover them. Carefully place the towel and seeds in a plastic bag, then seal it. Place the bag somewhere between 65-80°F (18-27°C).

Check every day until you see some sprouts. It’s helpful to consult seed germination times to get an idea of how long it will take each type of seed to germinate. You can stop counting about a week after you see the first seed germinate.

Interpreting the Results

Divide the number of seeds that germinated by the total number planted to come up with the germination rate. For example, if 17 out of 20 germinated, you would divide 17 by 20 to reach a germination rate of 85%. If 14 germinated, the germination rate would be 70%.

You can use your results to determine whether you want to keep or toss your old planting material. A germination rate below 75% means you may want to order new ones. However, you can also use the germination rate to inform your planting practices.

For example, if you have direct-sown crops like radishes or carrots with a germination rate of 70%, you can keep them but plant them closer than you usually would. This tighter spacing accounts for the decreased germination rate. If you want eight broccoli plants but have a low germination rate, you may want to sow 12 or even 15 seeds.