Vermiculite is a mineral that is used in multiple applications, from home insulation to gardening. After mining, vermiculite is heated until it changes into the worm-like pieces familiar to many gardeners. Vermiculite can be mixed with potting soil, peat moss, sand, or any combination of substrate. Some commercial growers use a combination of equal parts of vermiculite and sphagnum peat moss for houseplants and hanging baskets and one part of vermiculite to three parts of peat moss for bedding plants. Vermiculite can also be used alone, to start seeds. It makes an excellent germination medium because it is sterile, free of weed seeds and holds water and air.
Pour vermiculite into the germinating container. You can use a pot or seeding tray. Run water over the container until it begins to drain from the bottom. Allow the container to sit until all of the water has drained.
Plant the seeds according to the package directions. Generally, small seeds are planted more shallow than large seeds. Some seeds, such as impatiens, are simply scattered on the surface of the soil and not covered.
Place the germinating container in a plastic bag, close the top and place it in the appropriate area. Most seeds require some warmth to germinate. The seed package will include instructions on ideal germination temperatures for your seeds. If you have a heat mat, place the bagged container on the mat, set to the appropriate temperature. Keep the container out of direct sun.
Remove the container from the bag when you notice the first sprouts. Fertilize them with an all-purpose fertilizer at 1/8 the strength recommended on the fertilizer package.