Growing vegetables indoors allows you to get a jump on the gardening season, and in the long run, ensures that you will have a greater harvest as the season progresses. Planting seeds indoors versus direct seeding them into the garden has many advantages. Starting your vegetable seeds indoors, either in peat pellets or in cell trays filled with prepared soil, affords you the ability to control a large number of variables. Seeds, and especially certain vegetable seeds, need very specific treatment and environment in order to grow, and by starting these seeds indoors, you are able to control such elements as humidity, heat, and sun exposure much easier. It is often times also much more efficient to begin the seedlings indoors so that when it is time to transplant them outdoors into the garden, you have a large healthy plant to work with.
Seeds that benefit from being started indoors are any types of vegetables that can withstand the shock of being transplanted outdoors when they have matured. Not all vegetables like their roots being disturbed and can even die off if the shock to the plant is too severe. Some varieties of vegetables, however, like Onions, Parsley, Peppers, Tomatoes, Broccoli, Brussels sprouts, Cabbage, Cauliflower, Celery, Eggplant, and Leeks, are perfect candidates. Vegetables that do not like to be disturbed include many of the root vegetables such as Carrots, Beets, Turnips, and Parsnips. Many of the root vegetables are what is known as cold-hearty, and can withstand colder temperatures, and can therefore be directly planted in the ground as soon as temperatures do not drop below 4°C for the season. Several vegetables that are a bit trickier, include, Corn, Beans, and Peas. These vegetables have a much more sensitive root system, and benefit from being directly planted once the season is right, normally after last frost when temperatures become milder and the hours of sunlight increase.
When your seedlings have matured enough, and once the weather and temperature outside is right, it is time to start thinking about getting your vegetables outside and into the garden. Typically, after the last frost, and when the outdoor temperature is mild, about 15°C, it is time to transplant your seedlings. If temperatures drop much lower than this during the night, wait another week or two until milder weather comes. Cold weather can rot the seedlings, and can shock them, even killing tender crops. When you are confident that the temperature and weather outside is optimal, you can begin to harden your seedlings to be transplanted. To do this, place your seedlings outside in a shaded area with filtered light, and gradually over the course of a week, expose them to more and more sunlight. Seedlings grown indoors are often quite fragile and soft, never having been exposed to the outside elements like sun and wind, and need to be hardened before being planted in the ground.
Once your seedlings have been planted in the ground, ensure that they are watered immediately. Some may droop or wilt as a result of being transplanted, but most will rebound after they have had time to adjust to their big move. It is important to not over water new transplanted vegetables, because they will not be able to use all the moisture around them, and will rot.