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Reposted via Mother Earth News
The Germination Process
All seeds contain specialized cells that mobilize and grow when the germination process is triggered by moisture, temperature and sometimes light. Moisture and stored nutrients energize the embryo, which contains the latent structures for a plant’s root, stem and leaves. Most vegetable seeds that germinate quickly (such as cabbage and tomatoes) enter their dormant state with mature, fully formed embryos. The carrot family is at a disadvantage, however, because most Umbelliferae seeds (think parsley, fennel and dill) need time for their underdeveloped ovaries to grow before they can sprout. Other slow sprouters — spinach, for example — have compounds that inhibit germination in their seed coats. These compounds have to break down in the soil before the root and sprout can burst forth into the world.
Oxygen is vital to the germination process. Until seedlings have leaves to enable them to use solar energy, they rely on the food reserves in the seed combined with oxygen found in the soil to grow new cells. This is why you should always use a light-textured potting medium to start seeds, and why over-watering can cause seeds to rot instead of grow.
Appreciating the hard work that seeds must do during the germination process will likely enhance your seed-starting experience. You can watch time-lapse videos online of fast-growing bean seeds germinating, but watching them in person is even more amazing. The seeds that impress me most are squash. By the time the seedling leaves shed the seed coat, the little plant is already supported by a small mountain of roots.
From the day they germinate, vegetable seedlings face challenges from fungi and bacteria in water, soil and air. The fewer troublemakers they face, the better they can grow, which is why using fresh seed-starting mix each winter is so crucial. Quality seed-starting mixes are formulated to discourage common soilborne pathogens that cause seedlings to rot, and to retain both water and air with ease.
You can make your own seed-starting mix by using either peat moss or coir as a base, and then blending it with compost that has been heated to 150 degrees Fahrenheit to kill any pathogens and weed seeds. Small amounts of vermicompost can be a beneficial addition when added to a seed-starting mix, but use no more than 10 percent by volume.
As a 2005 study from North Carolina State University revealed, it’s not the precise mixture but what’s on top of the soil that counts most. Differences almost disappeared between commercial organic seed-starting mixtures and various homemade mixtures after all of the seeds were covered with vermiculite instead of a planting medium.
Made from two naturally occurring minerals, vermiculite has unmatched natural talents in seed-starting mixtures: It can absorb and retain several times its own weight in moisture while still holding some oxygen. (Regulations that require regular inspection of processing facilities have addressed concerns about possible asbestos contamination in vermiculite. The Organic Materials Review Institute has approved the use of the Therm-O-Rock brand.)
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