Welcome to Book of the Week – a weekly feature of an Acres U.S.A. published title offering you a glimpse between the pages! Get the Book of the Week email newsletter delivered directly to your inbox! This week’s Book of the Week feature is Made From Scratch, by Louise Placek.
The process of germination is truly one of the great miracles of nature. Against many formidable odds, these packets of genetic material and potential have covered the earth with new life year in and year out, century by century, millennium by millennium. The progression from seed to seedling to mature plant is nothing short of magic.
Only when the time is right does the seed begin the process of growth and development. The first thing that happens to start germination is the taking in of water by the seed. The seed coat is softened; easily in the case of a thin skin, or more slowly in a seed with a thick coat that needs mechanical or chemical help. Either way, there is eventually a break in the seed coat, allowing the internal components of the seed to soak up water and swell. This process is called imbibition (Pronounced: em bi bish’ yun) and is not unlike what happens when you put a dry sponge in a pan of water. The seed will usually swell to about twice its original size by the time the embryo begins to respond and grow.
Along with water, oxygen is needed by the seed to begin the conversion of all the stored nutrients (in the cotyledon) into usable form by the embryo. That is why a loose soil is best for germination, as it has plenty of air space to supply needed oxygen. The following are terms that are used to describe various aspects of germination:
Viability
This is a term describing the probability of a seed to germinate or not. If a seed is viable, then it is likely that it will germinate successfully if all the environmental factors necessary for this to happen are also in place. A small amount of moisture is needed inside the seed at all times (less than two percent of its weight) to maintain its state of viability. A seed can become non-viable (essentially dead) if it is allowed to dry out completely. Also, some seeds actually need extreme temperatures (either cold or hot) to make the embryo fully viable (developed) and ready for germination.
Dormancy
This is the suspended, non-active state of a viable seed before germination takes place. Many viable seeds can stay dormant for an indefinite amount of time as long as the seed coat remains intact. Seed banks around the world keep supplies of valuable and potentially threatened (almost extinct) seeds in cold, dry storage to maintain their genetic heritage. In nature, viable, undamaged seeds will stay dormant in the soil until conditions are perfect for germination.
After-Ripening
This is something that happens in many seeds after they leave the fruit vessel. It is sort of like the process an infant goes through in the womb. In animals, if a baby is born before it is developed enough, it will likely not survive. In some seeds, if the after-ripening process is not finished, then the seed may not germinate. After-ripening can be very fast or very slow, depending on the plant and environmental circumstances. Often, in a batch of seeds dropping from the parent plant, the after-ripening process happens at different times for each seed. This is an evolutionary precaution developed by plants to ensure that all their seeds will not germinate simultaneously, which could end in extinction if something happens to kill all those plants at once. In some cases, the after-ripening process can take years.
Scarification
This is the process of thinning the thick, tough seed coats of some seeds. As mentioned before, the layer can be removed over time via decomposition from bacteria and fungi, or mechanically by having it ground off by coarse soil granules, assisted by rain and wind. It can also occur when the seed travels through the gut of a bird or mammal. By being exposed to digestive enzymes as it travels through the alimentary tract, it softens and thins the seed coat, making it perfect for germination, leaving the body in a pile of ready-made fertilizer. Some plants have this planned out perfectly by offering their seeds in bright colored, delicious berries, irresistible to birds or other foraging animals.
Scarification can also be done manually by growers trying to germinate these seeds. Tough seed coats can be scored with a knife, sanded with sandpaper or a nail file, boiled in water and even soaked briefly (one to five minutes) in sulfuric acid. Another method is to paint the inside of a jar with glue and pour sand into the jar, rotating it until all the surfaces are covered with a layer of sand (this can be repeated to give you a good thick layer of sand). When this dries thoroughly, put your seeds into the jar with a lid and shake the jar until the surface of each seed is sufficiently scratched. Horticulturists all have their favorite, foolproof way to break down the skin of these seeds.
Some seeds have an inhibiting chemical attached to their seed coat that must be washed off before they can germinate. This is often coordinated by the plant so that a specific amount of water (rain) is needed to wash away the chemical, which incidentally is the same amount needed to germinate the seed, and usually occurs at the optimum time of year (fall through winter). This is to prevent the seed from germinating after a brief shower at times like the middle of summer, when high temperatures and mostly dry conditions would quickly diminish the seedling’s chances of survival.
Stratification
Many seeds from native plants require specific conditioning called stratification, to be ready for germination. In the temperate part of the world (where hot and cold temperatures are generally not extreme), scores of native plants shed their seeds in late summer or early to mid-autumn to allow them to go through this conditioning process before spring. The seeds are moistened by the usually ample rains of fall, seasoned by the cold winter temperatures (a sort of afterripening that helps them develop), so when spring brings warming conditions, they are ready to germinate.
Conversely, many desert seeds fall in the spring so they can be conditioned by the very hot temperatures of the desert floor (up to 120° F or 50° C) through summer, before germinating in late summer or fall when the autumn rains come. A rare few desert seeds actually need the scorching of fire to ready them for germination when the monsoons come. They grow in areas where wildfires from lightning are not uncommon. The parent plants burn to the ground, raining their nutrient-rich ashes onto the desert floor giving the scorched, ready seeds a perfect environment to come to life.
If you want to germinate native seeds artificially, then you have to mimic the conditions they require to ripen. In the first case, they can be placed in a moisture-proof bag between moistened paper towels or mixed into moist vermiculite (peat moss may be too acidic) and kept in a refrigerator or freezer (depending on the type of seed) for a month or two before attempting to germinate. In the case of the desert seeds, they may be heated in an oven (for up to a week at 120° F) before attempts at germination will be successful.
If you are going to germinate wild, native seeds, it is a good idea to find information on the stratification needs of the individual seeds before embarking on this method of growing. There are now good books available on native plants and information about specific plants can often be obtained on the Internet, from the USDA, or from universities that have strong botany or horticulture departments. Most U.S. states and Canadian provinces now have native plant societies that present a wealth of information about the needs of endemic plants. It is a fascinating and challenging endeavor.
Light Requirements
To germinate, most seeds have specific requirements for light. Some need light, some need darkness, and some are not particularly picky either way. A general rule of thumb for planting seeds is to cover them with an amount of soil that does not exceed the size of the seed. Basically (although there are exceptions), the bigger the seed, the deeper it should be planted. Very tiny seeds (the ones that look like grains of fine soil) need only be sprinkled on top of the soil and gently misted with water to settle them in. Covering them with any soil would be too much. Most seed packets have planting depth on the label so there is no mistake what the light requirements are.
Soil Temperature Requirements
Seeds are also fairly picky about soil temperature in order for germination to begin. Commercial growers of bedding plants often have heating mats on large benches where seeds are germinated early, to be sure plants will be ready when people want them in the spring. In the wild or in the garden, seeds will only begin germinating when they are good and ready. For the most part they can’t be fooled. The soil temperature is either right or it’s not. In Texas people are obsessed with tomatoes, and they always try to put them in the ground too early in the spring. I have told people repeatedly that tomatoes will not actually grow until the soil is warm enough, so they might as well wait until the time is really right.
Moisture Requirements
Seeds need water to germinate. The amount may vary, but a general rule is to keep the soil moist (like a wrung out sponge), but never soggy. Once germination has begun, do not let the seeds dry out. This is death for a tiny seedling. Even wilting can cause too much stress in the emerging plantling, causing it to die or become stunted. Read the directions on the seed packet for any special moisture requirements.
About the Author:
Louise Placek undertook the transition from a 20-year traditional career in nursing to the unknown world of owning and operating a small container plant business. With her husband Chris, she bought a hilly, 22-acre site with sandy loam soil, lots of prairie grasses, an oak and cedar woodland with wonderful wildflowers and a 50-mile view. Misty Hill Farm and the container business grew into a successful commercial venture all without the use of the standard industry chemical fertilizers and pesticides. Louise had a mission to grow outstanding plants commercially using only natural, earth-made products. A challenge at times – because there wasn’t a manual or mentor to turn to – it has become a very worthy cause.