Germination is the process in which plant seeds sprout their first root and stem. Germination begins when new growth bursts from the seed coat and ends when seed sprouts emerge at the soil's surface. Exact germination time varies among different plants; peppers take one to two weeks while watermelon seeds germinate within three to five days. Several specific conditions must be met for successful seed germinating.
Water starts the germination process. Before introduction of water, seeds contain less than 10 per cent water content, which keeps the seed dormant. Water absorption causes an enzyme in the seed's embryo to activate, resulting in increased respiration and duplication of plant cells. Presoaking the seeds before planting starts germination. Wrapping the seeds in a saturated paper towel allows the seed to absorb water and receive oxygen. When planted, water the seeds, but do not soak the soil.
While water activates the seed's embryo, oxygen starts the seed's respiration. Over-watering, planting too deep and soil compaction prevent seeds and future roots from receiving the oxygen that promotes germination and growth. Tilling your flower garden by hand with a pitchfork or mechanical garden tiller aerates the garden or potting soil to aid germination.
Even when water and oxygen are available, many types of seeds refuse to germinate if soil temperatures are too low. Most seeds germinate at soil temperatures between 20.0 and 30.0 degrees C. Cool-season plants and some warm-season plants may tolerate lower germination temperatures. Few plants germinate at temperatures lower than 10 degrees C.
Not all seeds need light to germinate. Light may prevent the seeds of centurea, larkspur and pansies from germinating. Determine the hours of sunlight needed to encourage and continue the process of germination.
Plant seeds at depths recommended for their type. Those depth recommendations ensure that seeds receive the amounts of sunlight and oxygen necessary to encourage germination. Some seeds have thick coats that water and oxygen cannot penetrate, so presoaking and scratching the seed coat help to break it down. Some seeds may not germinate if they are more than 1 year old, although some seeds grow successfully when planted 5 to 6 years after purchase.