One topic that many people find overwhelming when deciding whether or not they want to grow their own tomato starts is lighting. There are so many sources nowadays, and the addition of LED lighting at a more affordable price point has caused even more confusion.
Natural lighting from a sunny southern exposure window is one source. While it’s not impossible to grow tomato seedlings using natural light, it can be very frustrating and the results can leave a new gardener feeling inadequate and may even cause some to give up. The sun’s strength from indoors during the winter is not going to be quite enough to keep your seedlings happy. They will “reach” and bend toward the window wanting more light.

Another type of lighting is full-spectrum meaning there is light across the entire spectrum of colors from infrared all the way to ultraviolet. These types of lights are purple and what many professional indoor growers use as they provide the same spectrum the sun does. Will they work? Yes. But are they necessary? Not in most cases. This type of light is only needed if you are going to grow indoors, year-round because they provide the lighting necessary for all stages of growth-vegetation, flowering, and fruiting. If you are only growing starts that will be planted outside, this type of lighting is a waste of money.

Now that we have crossed off two types of lighting, let’s crack to code of watts, lumens and kelvin units so that you will be able to easily decide next time you are ready to pick out grow lights for your seedlings.
Watts signify energy use or consumption. This number can range widely, but the lower the number, the less power you will be using. LEDs are a newer type of lighting and use considerably less energy, so you might want to consider an LED fixture if it fits your budget because it will save money in the long run.
Lumens are related to the brightness or reach of the light from the bulb or tube. The brighter the better because seedlings grow at a rapid pace, soaking up light for plant cell photosynthesis. If your lumens are too low, your plants will begin to reach, just like they would in a sunny window. 1,000 lumens or higher is recommended.
Kelvin units are what gives a hint of color to the light source. Low kelvin will produce a yellowish light that can run too hot and burn your seedlings’ delicate foliage. High kelvin light will give off a cooler blue or “daylight” tone and insure that your bulbs are safer and can be placed nearer to the plants without causing burn damage. A kelvin rating of 5,000 or higher is best.
Once you have your lights picked out and have seedlings growing, make sure to keep your light source around two inches from the tops of the seedlings to insure a steady growth rate with minimal stretching.