Seed Germination

Seed Germination

Late winter is the time of the year to dig out those old seed packets and see if the seed is still good. You may use up a whole packet of beans, carrots or lettuce in one year, but usually there are enough seeds of tomatoes, cucumbers, squash and peppers to last for several years. Just because you have seed left, however, doesn't mean that it is good seed.

Before I launch into a description of how to test the seed, let's talk about seeds a bit. We have all planted seeds, but how much do you really know about them? Learning more about seeds can help improve your success with them.

Seed Parts When you look at a seed you are looking at the seed coat. As people wear coats for protection from foul weather, seed coats perform much the same function. They provide protection against entry of parasites, against mechanical injury and, in some seeds, against unfavorably high or low temperatures.

Inside the seed coat is the embryo, an immature plant with all the parts of the adult plant. A close look shows leaves and a root -- they may be tiny but they are the beginnings of a plant. The seed's embryo leaves are called the "cotyledons." The seed is filled with "endosperm," food that will nourish the embryo during its early stages of development.

Germinating Seeds Germination is a fascinating process. Seeing a tiny seedling emerge from a dry, wrinkled seed and watching its growth and transformation, is observing the mystery of life unfolding. The first sign of germination is the absorption of water -- lots of water. This activates an enzyme, respiration increases and plant cells are duplicated. Soon the embryo becomes too large, the seed coat bursts open and the growing plant emerges. The tip of the root is the first thing to emerge and it's first for good reason. It will anchor the seed in place, and allow the embryo to absorb water and nutrients from the surrounding soil.

Some seeds need special treatment or conditions of light, temperature, moisture, etc. to germinate. Seed dormancy is very complex, but it protects that living plant material until conditions are right for it to emerge and grow.

Practical lessons can be learned from the seed:

Seeds with bigger amounts of endosperm can feed the embryo plant longer, while it works its way toward light. Therefore, big seeds can usually be planted deeper.
Seeds must absorb water to get germination going. Therefore, presoaking seeds may speed up the process.
Available water is important to the newly emerged root. Therefore, you should plant seeds a little deeper in the middle of summer, when the top of the soil dries out quickly.

You get the picture; so now let's talk about germination testing. Whether left-over seeds will germinate (sprout) and grow depends on how old they are and how they have been stored. With proper storage conditions, the average useful life of some common vegetable seed is much longer than some others.

1-2 years:	3-4 years:	5-6 years:
corn onions and leeks parsley parsnips peppers	asparagus beans and peas beets cabbage family carrots eggplant squash and pumpkins tomatoes	cucumbers lettuce melons spinach

If you keep your seeds cool and dry, they will last longer, but can you be sure that they are still good? If they are, you can save yourself some money. Before you order your new seed, do a germination test on any seeds more than just one year old. Here's what to do:

Put exactly ten seeds on top of a damp, folded paper towel.
Put the towel and seeds into a plastic sandwich bag and seal.
Label the container with the date and seed variety being tested.
Leave at room temperature for a week or so. (Leave parsley, carrot and celery longer; they're slow.)
Count the number of seeds that sprout:
- 10 = 100% or perfect germination
- 9 = 90% or excellent
- 8 = 80% or good
- 6-7 = 60-70% or poor -- sow more thickly
- 5 or less = 50% or less -- throw the seed out!

By Holly S. Kennell, WSU Extension Agent, King County

For more information contact your local WSU Extension Office.