[Seth Gregory]

I am Seth Gregory I am doing a senior project on how light spectrum affects plant growth and these are my question for you.

How well do colored growing lights work for growing plants?
How fast does colored growing lights allow plants to grow?
Do colored growing lights affect growth rate of plants?
How long do the growing lights need to be on the plants a day?
How long will it take the plant to start growing if i put the lights on for 3 hours a day?
Do you have any experience with what colored growing lights work best?
Do cool growing lights work better than warm?
What color growing light works best to grow plants faster?
How well does red and green growing lights grow plants?
How well does orange and blue growing lights grow plants?

[Eric Vinje]

Hi Seth –

Most growers tend to favor florescent or high pressure sodium lighting systems (HPS). Florescent lighting systems tend to be a bit more wallet friendly for seed starting or small vegetable growing systems. HPS works well for larger growing set ups or indoor farming production. Some growers utilize LED lighting, though I’d say it’s quite rare (at least in Montana) to see a grower using solely LEDs outside of the research field. LED and HPS are very comparable in terms of plant growing habits, and you’ll see a similar return on investment as far as wattage and plant growth are concerned. A LED system can cost 2-4 times the amount of money an HPS system will cost upfront. However, LEDs are quickly gaining popularity due to their energy saving capabilities and long lifespan. For a bit more in-depth descriptions of different plant lighting systems, check out info pages here and here.

As a general rule of thumb, a red spectrum of light is prescribed for flowering or fruiting plants, a spectrum that is more blue works better for vegetative plants. Individual LED lights usually come in seven colors: red, magenta, purple, blue, white, ultra violet (uv) and infrared. Some system’s such as the Kessil LED utilizes just one targeted light spectrum. Other LED systems will house many different targeted spectrums, such as this California Light Works System. Plants grow best under natural sunlight. With this fact in mind I would recommend a “broad spectrum” LED that offers multiple different colored lights within one light board.

Daylength and growth habits will vary between plant species. Photoperiod is the term used to describe how day length affects plant growth. Plant species are classified into three different photoperiod groups, short-day, long-day, and day-neutral plants. These three groups require different lengths of daylight in order to thrive and eventually flower. For your experiment, I would suggest focusing on one type of plant, such as tomatoes, herbs, or salad greens. A little bit of research will help you decide which species of plant will work best for your experimentation needs.

I hope this is a nice starting point for your research. Peer reviewed scientific studies pertaining to LED lighting will be of immense help to answering specific questions. Good luck with your senior project!

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