KC Gardens

To start plants from seed, let your light shine

Transplants such as these zinnias flourish with the right amount and intensity of light.
Transplants such as these zinnias flourish with the right amount and intensity of light.

Many of us had our first experience of starting plants from seeds when we were children. Think back to the marigold in a milk carton on the windowsill. The result was a long, lanky plant that did not look like anything grown professionally in a greenhouse.

Starting high-quality transplants at home where low light is an issue is not difficult. Stocky transplants require more light than even the brightest window. Once you know the trick you can grow a wide range of garden plants with just a little care.

Light it up

Growing transplants requires bright light that is not available in the home. The secret is to provide artificial light. Shop lights are widely available and economical.

Standard shop lights have fluorescent tubes, and newer models come in a wide range of LED styles. Either style works for growing transplants if a few rules are followed for getting the most out of the light source.

Let it shine

There are two keys to using shop lights. The first is duration: For the developing seedlings to get enough light the fixture must be on at least 16 hours a day. Better yet, leave it on nonstop.

Sunlight does not last that long, of course, but sunlight is far brighter than the shop lights. Compensate for this lower intensity by lighting up the plants longer.

Growing seeds with lights
Keep the shop light 4 to 6 inches above the tops of the transplants. Adele Wilcoxen

Keep it close

The second key to success is brightness. As the light moves away from the source the intensity decreases. Short, stocky transplants are produced under the highest intensity of light. Remember the school project when the result was long and straggly? That is because the plants were stretching for the light.

The light source should be no farther than 4 to 6 inches away from the top of the growing plants. The supports for the light fixture need to be mounted in such a way that the lights can be lowered at first but then raised as the plants grow. An adjustable chain or some other system works fine.

Skip the expensive “grow lights”

This combination of long periods of light and high intensity allows basic shop lights to serve as grow lights. There are more expensive grow light fixtures and bulbs on the market, but they provide little added benefit. In order for them to be effective, the same rules apply.

The only advantage of grow lights is they provide a wider color spectrum, which is important for flowering and fruiting. This spectrum is not necessary for short term crops like transplants.

Now is the time to begin starting your seeds. It is a great way to get new plant varieties and have a little fun during the winter months.

Dennis Patton is a horticulture agent with Kansas State University Research and Extension. Got a question for him or other university extension experts? Email them to garden.help@jocogov.org or visit KCGardens.KansasCity.com