To promote germination and ensure healthy seedlings, you need to provide seeds with three fundamental elements:
This is the part that most new gardeners ignore because it doesn’t seem as important as water and light. But trust me: Unless your room is very toasty, you will increase the odds that heat-loving seeds like tomatoes and peppers will sprout (and sprout quickly) if you keep them warm with a heat mat. There are exceptions, so read the packets for instructions, but most seeds germinate between 60 and 80 degrees. Remember that wet soil is 5 to 10 degrees cooler than the surrounding air.
Related: How To Start Seeds On A Kitchen Table
Seeds won’t sprout without uniform, moderate moisture. Too dry and they stay dormant; too wet and they rot. Professional greenhouses use overhead misters rather than hoses, whose flows can pop seeds out of their compartments. At home, you can simulate a misting system with a spray bottle and a humidity dome, a ventilated plastic lid that keeps moisture in.
Once germination begins—and for some flowers, even before that— bright light is essential. Short days and a distant sun in late winter leave inadequate natural light in most of the Northern Hemisphere just as it’s time to sow seeds. Rely on artificial grow lights for the 14 to 16 daily hours of high-quality light that seeds need to become productive plants.