Factors Affecting Germination of Seeds

Soil

• Seeds need an appropriate growing medium in order to emerge and develop. According to the North Carolina State University Extension, the best growing medium for seed germination is soil that's fine-textured and has an even consistency, as well as loose and well-aerated. Your growing medium also needs to be free of any harmful pathogens. If you make your own soil mix, the Iowa State University Extension recommends pasteurizing it in order to destroy pathogens. Lightly moisten the soil, place it in a baking pan and bake in the oven for 30 minutes at 180 degrees Fahrenheit.
  
  

Light

• Light requirements for germination vary by plant species. Some plants, such as verbena, portulaca, petunia, phlox and pansies, require dark conditions in order to germinate. Others, such as begonias, coleus, geraniums and impatiens, need a good amount of light. Others aren't picky and will grow in either light or dark conditions. Seeds of plants that need light should be planted near the surface of the soil so they receive adequate light. If you germinate seeds indoors, be sure to provide supplemental light if plants require it.
  
  

Water

• Water absorption is the first step in seed germination, according to the North Carolina State University Extension. Soil should be kept moist at all times for best germination results. Be careful, however, that you don't drown the seeds or flood the soil, since this may cause seeds to dislodge from the germination site. If you germinate seeds in a seed starting kit, you can cover the kit with plastic wrap to trap moisture. Poke several holes in the top, though, to keep air circulating inside.
  
  

Temperature

• Some seeds are very sensitive to soil temperature, whereas others can germinate in a wide range of temperatures. Tomato seeds, for example, have a minimum germination temperature of 50 degrees Fahrenheit and a maximum of 95 degrees. According to the North Carolina State University Extension, most seeds germinate at 65 to 75 degrees. Excessively high or low temperatures will prevent germination or slow it down significantly. If you start seeds indoors, be sure to move them to a cooler area once the plants have emerged.