Plastic bags can serve as seeding pots as easily as any other container. Use plastic sandwich bags for individual seed pots. For larger plantings, such as squash, use a plastic grocery bag. Plant three to five seeds per bag. Plastic bags are a quick and easy potting solution for locations with short growing seasons, which necessitate starting seeds early indoors.
Pour commercial potting soil into a plastic sandwich bag until it is no more than an inch from the top. Use bagged potting soil from a garden center, because it likely will be free of disease or weed seeds. Fill additional plastic bags for other seeds you are starting.
Press the bags into a tray made of a non-leaking material, such as plastic or metal, to protect your home from any spills or leaks. The soil in the bags should form a flat bottom, so they don't tip over.
Plant your seeds in the bagged soil. Always follow the directions on the back of your seed packet for the depth of planting, because each type of seed will be different. The rule of thumb is that you plant a seed three times deep as it is long.
Spray the top of the soil with water from bottle mister. You want to soil to remain moist, but not soaked. Check each day and spray more water if the soil begins to dry.
Zip the top, if you are using zip-locking bags, leaving just a tiny bit open to create a warm, moist environment for seed germination. If you are using flip-top sandwich bags, pull the flap over the top of the soil.
Place the tray filled with seeded plastic bags near a sunny window.
Open the top of the plastic sandwich bags when the seed germinates (green sprout comes through the soil). Continue to mist the soil when it starts to dry.
Plant your seedlings when they reach a height of 2 to 3 inches and the last frost has passed in your part of the country. Gently cut two sides of the plastic bag from top to bottom with a sharp scissors. After you have dug holes outdoors or in a planter, slide your hand under the bottom of the soil and place it in one of the holes. Work soil around the new seedling, gently patting it on top of the soil for structure.