Heated propagators can overcome this by keeping your seeds at a conformable, ambient temperature. They can be used to grow seeds early in the season, to give them a head start or to raise more tender plants originally from warmer climates.

Plants like tomatoes, bell peppers and squashes need a long growing season in our cooler temperatures to ensure they have time to grow, produce fruit and for those fruit to ripen. Germinating them indoors in a heated propagator early in the year, when outside it would be much too cold for them to grow, ensures they get the long growing season they need.