The best tips for seed germination apply to almost all seeds, but their effectiveness will depend on how old the seeds are and what type they are. The primary ways to aid in seed sprouting are to introduce the presence of water; create a flaw in the seed shell, if possible, such as a nick, crack, or cut; and to alternate temperature levels. The embryo of a seed is sustained by endosperm, a form of food source that keeps it alive in a dormant state. Though some seeds can seem to last forever before use, such as varieties of lotus known to survive for over 2,000 years, others such as maple seeds need to be germinated within two weeks or they will die.
Pre-soaking seeds overnight in water prior to planting them is an effective first step in seed germination. For small seed or those that tend to sprout easily, placing them inside several layers of wet paper towels will provide enough exposure to water. If the seeds are old and seed germination is questionable, other steps should also be taken before they are planted in the ground or in a container.
Larger seeds will benefit in seed germination success if you nick the seed coating slightly prior to planting it. The testa, or seed shell, should be gently breached with fingernails or a fine piece of sandpaper on a side of the seed away from where it sprouts. Soaking them in water or wet paper towels after this will give the embryo inside an easier time at penetrating the testa.
Temperature changes can help with seed sprouting as well because it mimics the processes of nature. Seeds that normally are dormant in the ground during a cold winter season can benefit by being placed in the freezer for a few days prior to planting. Other seeds of plants native to warmer climates that get wet and cold in the winter, but not extremely so, will benefit by being placed in a wet environment in the refrigerator. Refrigerated seeds can be planted first and watered as long as the surface of the pot is covered so that the moisture doesn't evaporate away.
Some gardening experts also recommend adding a small amount of dish detergent into the water that the seedsare soaked in. This changes the composition of the water slightly, allowing it to more easily penetrate the seed testa. Basic liquid soap, if diluted, has no adverse effect on most plants, from seed germination to mature stages, as long as they continue to receive adequate water and sunlight.