Starting seeds indoors has a ton of advantages -- starting from seed is cheaper than buying seedlings, you can harvest a plant's bounty earlier, and if you use uncontaminated soil, your seedlings can be stronger and healthier than factory-raised specimens. Plus, if you save your own seeds over the years, you can create one-of-a-kind varieties that will be the envy of heirloom gardeners the world over.
To get started, fill a clean container, such as an egg crate, seed starter box, peat pot or deep ice cube tray, with uncontaminated growing medium. The container must drain well, so punch holes if necessary. Plant the seeds according to package directions and place the container inside a large, loose, transparent plastic bag. The bag will raise the temperature and humidity of the growing atmosphere. If the seeds require sunlight to germinate (not all do), place them in a warm sunny spot and turn the container often to make sure stems grow straight. Check the soil frequently and ensure that it's moist (but not sopping wet). Add fertilizer once the seedling has four or more leaves. Cool season crops such as broccoli, cabbage, celery, leek and a variety of lettuces can all start indoors from seed in the winter months.
To give tender seedlings their best chance for survival, you'll need to harden them off in a cold frame or a cloche before planting in the ground. Learn how to create a cloche in the next section.