Starting plants from seeds indoors is a great way to grow a wide variety of plants. If you are only going to start a few plants, a roomy window sill at a south-facing window may be all the growing space you need. However, window sills can be the coldest place in the house, especially at night, and the hottest during the day. Instead, choose a place safe from heavy traffic, pets, cold drafts, and excess heat.
Rather than solely relying on natural light, it is better to grow seedlings under fluorescent lights. Hanging lights from chains will allow you to raise them as the plants grow. Ideally, the lights should be about two inches above the tops of your seedlings, but no more than four inches. Plants need 12 to 16 hours of light a day, but do not leave the lights on continuously.
A constant heat source underneath can also be beneficial to seedlings. Seeds of most plants started indoors produce healthier roots when the potting mix is warm. Electric heating mats specifically for seed starting are available from most garden centers and available online.
Whether you use cell flat containers or small plastic pots, all seed starting containers need to have drainage holes at the bottom. Set the containers into a solid tray; fill them with potting mix and water. The potting mix will settle down into the containers, add more potting mix and water again, until the containers are about 2/3 full.
Once the seedlings start to outgrow the original pots, transplant them into larger containers. When transporting, be sure to lift seedlings by the root ball; never hold the seedling by its stem.
Plants started indoors have not been fully exposed to the outdoor elements. They should be gradually introduced to the outdoor environment, a process called “hardening off,” or their leaves may be damaged or the plant can wilt.
A couple of weeks before planting outdoors, start hardening off the seedlings by bringing them outside for increasingly longer periods of time each day. Start by putting them outside in the shade for a few hours. Be sure to bring them back inside for the night before temperatures drop. Leave them out a little longer each day.
Finally, once they have been hardened off, seedlings can be transported outside, preferably on a cloudy day or late afternoon.