What You Need To Know About The Germination Process
Knowing a little about the seed germination process can make a difference in the quality of crops or the health of a plant you are starting from seed, and can a lack of knowledge can sometimes result in no germination at all.
The germination process is quite similar for most seeds, although some seeds require rather specific conditions to successfully germinate. Most of the seeds you plant in your garden require oxygen, water, light and the right temperature. For certain seeds however, darkness is required if the seeds are to sprout. Other seed types have very hard outer shells, which must be scuffed or scored to ensure germination. Seeds such as apple seeds need to be kept cold for an extended period if they are to sprout, and some seeds remain dormant for years until touched by fire, which gets the germination process started.
Whether the seed in question is the size of your fist, or as small as a typical poppy seed, or smaller, the inner structure is somewhat similar. Each seed is made up of a hard shell, designed to protect the interior, in which there is an embryo and endosperm. Endosperm consists of a food supply for the embryo, and is somewhat equivalent to the egg white in an egg. When the germination process starts and the embryo begins to grow, it could be considered comparable to a fetus growing in a human womb. The embryo contains all the parts found in the adult plant, though obviously very, very tiny. Under a microscope however, the presence of leaves and roots can be detected.
Moisture Is A Necessity - For germination to get underway, moisture must first penetrate the outer shell. This is an easy process in some types of seeds, and can be very difficult or time consuming in others. Some seeds we plant have a germination time measured in a very few days, for other seeds the germination process may not occur for months once they have been placed in the soil.
Once moisture penetrates the seed shell, an enzyme is the released which causes the embryo's cells to begin to duplicate, and growth of the tiny plant begins. As weak as the tiny plant may appear to be, and as tough as the seed shell is seen to be, once the embryo reaches a certain size and things begin to get crowded, it manages to burst through the shell, usually roots first, and shortly thereafter the plant becomes visible as a tiny sprout.
Soil Depth Is Important - A seed contains sufficient endosperm to provide nutrition for the young plant until it can start drawing nutrition from the soil and through its leaves. The supply of endosperm has definite limits of course, which is one reason why when seeds are planted too deeply they may never sprout. The depth of planting instructions found on seed packets are there for a reason. As a rule of thumb, the larger the seed, the deeper it can and should be planted.
Seed Age A Factor - The age of a seed can also be a factor in its ability to germinate. As mentioned previously, some seeds can lie dormant for years, waiting for the right conditions to occur before they will germinate. Other seeds, such as many garden seeds, may only have a shelf life of a year or two. Some flower garden seeds need to be sown shortly after they are harvested as their shelf life is a matter of a few weeks or months. Seeds for vegetables such as corn, onions, and peppers will often not germinate if they are more than 2 years old, while bean seeds, carrot and tomato seeds, and seeds of the cabbage family have a shelf life of 3 to 4 years, and with most melon seeds, cucumbers and lettuce, the germination process will be successful to 6 years after the seeds were harvested if kept under the right conditions, the right conditions usually meaning a cool and dry place.