Can I use my old garden seeds?

This is the time of year when sowing seeds for transplants is beginning to kick into high gear. Gardeners are looking through their seeds they saved from past years and are trying to decide which ones they can use.

Seed packets have a “packed for” date that sounds like it is an expiration date. It actually indicates that the seed was grown the previous season for use in the current season. They are fresh and meet certain minimum germination rate requirements required by federal law.

The definition of the term “germination” according to the Federal Seed Act is: “… the percentage of seeds capable of producing normal seedlings under ordinary favorable conditions (not including seeds which produce weak, malformed, or obviously abnormal sprouts)." This is tested by using federally prescribed methods so that seeds grown in various states can be accurately compared.

Because not all species of plants produce seeds that have the same natural germination rate, different kinds of seeds must meet different requirements. Pepper seeds, for example, have a 55% minimum germination rate requirement, onions are at 70%, while cucumber, lettuce and several others have an 80% requirement.

Keep in mind that these are only minimum requirements. Most reputable seed sellers voluntarily exceed the federal minimums.

Every year, I get asked by gardeners about the viability of their old seeds. Each vegetable seed has a typical longevity, meaning it has an acceptable seed germination rate at a certain age. As seeds get older the germination rate decreases over time, so more seeds may be needed to get the same number of plants.

Moisture, especially in the presence of heat, is the enemy of stored seeds. Stored seeds exposed to moisture can begin to germinate in the package, then stop once they dry out again. By that time however, the seeds are weakened and the germination rate will be lower. So seeds must always be stored in a cool, dry location in well-sealed containers.

Here is a chart of seed longevity that I put together from a number of different sources. It’s one I like to put out every year since so many people ask about this subject.

Copy it to your phone so it is handy when you need it, or print it off and stick it on your fridge.