Some plant varieties produce seeds with impermeable seed coatings. These hard coatings require softening before the embryo inside can germinate and break through the hull. This occurs naturally during the winter as the seeds freeze then later thaw--the moisture and stress weaken the seed coating. Other times birds or animals provide the necessary stress either by eating the seeds and weakening them with digestive fluids or pecking at them and scarring the seed coating. Seeds that require soaking include morning glories, moonflowers and strawberry seeds. Most seeds that require soaking also require cold temperatures to break dormancy.
Place seeds in a plastic bag filled with moist sand four weeks prior to the recommended planting date for the seed variety. Keep the bag in the refrigerator for four weeks to simulate cold weather.
Remove seeds from the bag and nick the seed coating with a sharp knife or rub with sandpaper. Only nick down to the white undercoating just under the hard outer coat.
Fill a bowl with hot tap water. Avoid boiling water as this will cook the seed inside the coating and kill it.
Place the seeds inside the bowl of hot water. Let soak overnight or at least 12 hours. Remove from water once seeds have noticeably begun to swell.
Sow seeds indoors or out according to the directions on the seed envelope for the particular variety. Seeds germinate within seven to 21 days, depending on the specific plant.