Propagating from seed gives you a greater choice of plants, as nurseries often only supply a limited selection of the most popular seedlings. Seed is also less expensive than purchasing seedlings, allowing you to add more plants to your garden for just a fraction of the cost of transplants. Start seeds indoors to ensure the best germination rates and to help ensure the health of the seedlings. Plant in late winter or early spring so that your plants have a head start on the growing season.
Prepare seeds before sowing if indicated on the seed packet. Soak seeds that require scarification (scratching, notching or wearing down hard seed hulls) in a bowl of warm water overnight or scuff the seed coat with a piece of sandpaper. Place seeds that require cold stratification in a plastic bag in the fridge or freezer for the time indicated on the seed packet.
Fill a seed-starting flat with a sterile, well-draining potting mix. Leave a ¼-inch space between the top of the flat and the soil. Use flats that have drainage slits in the bottom.
Set the flat on top of a drip tray. Water the soil until the excess moisture drains into the tray. Leave the flat to soak in the water for four to six hours so that the soil becomes evenly moist, then drain the excess water from the flat.
Sow seeds to a depth twice that of their width. Plant the seeds 2 inches apart in all directions. Some seeds may specify they require light for germination; plant these seeds on the soil surface.
Cover the flat with a sheet of plastic wrap, which helps retain soil moisture during germination. Place the covered flat in a dark, 65- to 75-degree Fahrenheit room unless the seed packet specifies light or a different temperature.
Remove the plastic wrap once seedlings emerge from the soil. Move the flat to a sunny windowsill in a warm 65- to 75-degree Fahrenheit room.
Water the seedlings when the soil surface begins to dry. Fill the drip tray with water and leave the flat to soak until the soil surface becomes moist, then drain the excess water. Bottom water prevents wet foliage and fungal diseases on the seedlings.
Fertilize the seedlings once every two weeks, beginning one week after they sprout. Apply a ¼-strength dilution of a balanced soluble fertilizer.