Heating seeds and seedlings indoors helps speed germination and increases the survival rate of the seedlings. Heating mats allow you to raise the soil temperature of the seedlings so they can grow before the actual planting season begins in your area. After the last frost, you can transplant strong, healthy seedlings to the garden. Electric blankets are an alternative to expensive seed heating mats and provide the same heating.
Lay the electric blanket on a flat surface, such as a table or the top of the refrigerator. Cover the blanket with a plastic shower curtain or other variety of plastic sheeting. The shower curtain will keep the blanket from getting wet or dirty.
Set the seedling tray on top of the plastic sheeting. Insert the soil thermometer into the soil of one of the seedling cells.
Turn on the electric blanket. If it has a temperature control, set it to 23.9 degrees Celsius. If not, leave it on until the soil thermometer reads 22.2 to 23.9 degrees Celsius. If the blanket doesn't have a temperature control, turn it off once it reaches the correct temperature range to avoid over heating the seedlings. Turn it back on once the soil temperature drops out of the desired range.
Remove the seedling tray from the blanket when you water the seedlings. Let the moisture drain out of the bottom of the tray, and then place the seedlings back on the warming blanket.
Each blanket brand has a suggested maximum use per day. Don't let the blanket run for longer than that suggested use or you may cause it to over heat. Consult your blanket manufacturer if you're unsure of your brand's maximum daily use.