Seed Viability

Seed packets1

Seed packetsIs the seed you have on hand still viable–will it germinate?

A seed contains an embryo–a partly developed root and stem, a supply of stored food, and a protective coating.

Seeds sprout through a process called germination. Germination–depending upon the type of seed–requires just the right conditions for growth–usually an abundant supply of water, an adequate supply of oxygen, and the proper temperature. Water causes the seed’s tissue to swell and break through the seed coat. Oxygen supports respiration, the burning of food stored in the seed necessary to supply the energy to grow. The correct temperature provides the optimal environment for growth.

A seed is viable if it is able to germinate under the proper conditions for that seed. Seed viability can range from a few weeks to 50 years. Most vegetable seeds are viable for up to three years, but not all.

If you have seed leftover from last season or the season before or if you have been given seed and are unsure how old the seed might be, testing seed viability can save you time and effort in the garden. Seeds can require a few days to more than a week or two to germinate; if you sow seed today and it later fails to germinate in a week or two you have lost time and wasted effort.

Seed more than a year old or seed that has been improperly stored–usually in a warm or humid place (seed should be stored in a dry place at temperatures just above freezing) may have lost some or all of its viability–the energy stored within necessary for germination. Old seed can also produce plants that are weak.

A simple check of seed viability can save you time and effort. Here’s a simple way to test germination and also estimate the rate of germination for the seed you have on hand:

Take a paper towel and write the name of the seed on it and the number of days to germination (you can get this number from the back of the seed packet or from a grower’s guide). Moisten the paper towel and count out 10 or 20 seeds onto the towel. Fold the moist towel so that both sides make contact with the seeds. Place the folded towel in a plastic bag or food storage baggie and seal it. Place the bag in a bright, warm (70°F) place and wait the number of days required for germination. Then open the bag and unfold the towel and count the number of seeds that germinated. If no seeds or only a few seeds have sprouted, you can put the seeds back in the bag and wait a few more days and then check again.

If the germination rate is low, buy new seeds or plant more of the old seeds than you would normally to make up for the low rate of germination. (Divide the number of sprouted seeds into the total number of seeds to get your germination rate for the total batch of seeds.) Seed packets–in addition to listing the number of day to germination–will often state the expected rate of germination.

Some seed needs light, not dark, to germinate. To test seed that is supposed to sown on the soil surface, place the seed on the moistened paper towel but do not fold it. Just slip the moist towel and seed into the plastic bag and count the number of days to germination.

Buying new seed each year will ensure optimal germination and stronger plants, but the large amount of seed in seed packets is usually more than a gardener will need in a given year. Extra seed can be put away until next year and should remain viable. Store extra seed in dry jar with a tight fitting lid and place it in the refrigerator away from the freezer section.

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. has more than 10 million visitors each year.

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