How Long Does It Take Seeds to Grow Using a Warming Pad?

Moisture and Heat

• Plants need moisture and the proper soil temperature to sprout. Nature provides both through rain and sunshine, but the indoor gardener has to supply his own. Water is easy, but getting the right temperature is harder. Too little heat and not enough seeds will sprout, too much and none will. When the seeds are kept in the preferred temperature range with a warming pad they normally sprout in six to 14 days. Temperatures lower than the preferred range cause the sprouting time to be longer.

Cool-Weather Seeds

• Each type of plant requires temperatures a little different, which means that using one warming pad may not work. Seed packages come with the preferred temperature ranges on the back. Lettuce, peas, spinach, carrots and radishes all tolerate cooler temperatures down to almost 40 degrees Fahrenheit. They are often planted earliest in the garden, and when started inside may not even need a pad. Parsley, parsnips, Swiss chard and beets prefer a little warmer soil and might need a warming pad.if the house temperature is kept cool.

Multiple Seed Planting

• Peppers, tomatoes, squash and pumpkins are good examples of plants that will sprout when a single warming pad is used to keep them all at the same temperature somewhere between 70 and 95 F, but for optimum yield each should really be kept at what they prefer. Peppers and tomatoes do best at 85 F, while pumpkins do best at 90 F and squash at 95 F.

Soil Temperature Considerations

• The depth of the soil in the pot, the pot material, the strength of the warming pad and the air temperature all influence the soil temperature. The only sure way to keep track is to use a soil thermometer placed 3 inches below the surface. If you need to put different seeds that need different temperatures on the same pad, then adjust the temperature for the highest level, and use padding or larger pots to keep the temperature at a lower level for the other seeds. Warm the soil several days beforehand to ensure it is the right temperature.