Let There Be Light
Jon Porter
www.PorterLearningCenter.weebly.com [email protected]
Three years ago, I started experimenting with growing lettuce, sunflower and broccoli greens, and several pepper varieties indoors under artificial lights. During the cold season (more than half of the year in North Idaho), my mountain cabin stays nice and toasty warm. I might as well take advantage of the warmth, add a few lights and grow food during the winter. If you are into gardening, why not set up to grow a few plants indoors? Why not have fresh pick-it-and-eat-it foods available all year.
Grow lights have been improved over the decade. T-5 HO (high output) Fluorescent lights are now available that provide increased light (measured in lumens) at lower cost per watt of power than standard fluorescents. The T stands for tube and the 5 stands for 5/8 of an inch in diameter. I now use 4 foot T-5 HO 54 watt lights for all of my indoor growing. One light will accommodate 2 standard 11“ x 22“ flats. They provide nearly 5000 lumens of light, the most bang for the buck for inexpensive grow systems. If you are just starting out with indoor growing, consider using the Jump Start 4 foot T-5 grow system available at the CO-OP in Sandpoint and can be purchased online. Note that these lights have a 6500k color temperature.
So, what is a 6500k color temperature? The K (Kelvin), in the context of lighting systems, is a measure of the color of a light source relative to a black body at a particular temperature. Well, that’s nice. What is important to us gardeners is that a color temperature of approximately 6000k is required to match "daylight". 2700k to 3500k bulbs provide higher output in the red spectrum of light which promotes flowering. 5000K to 6500k bulbs are full spectrum with much of the light in the blue spectrum which promote overall green plant growth. So if you are going to have only one bulb, it makes sense to use one that has a high color number between 5000k and 6500k. This year, I intend to purchase several 2 bulb T-5 light fixtures and experiment with mixing a 3000k and a 6500k bulb in each fixture for growing flowering plants.
Garden books will teach us that different plants require different amounts of light, but don’t let that stop you from trying to grow any plant you like indoors. As a point of reference, direct sunlight provides up to 100,000 lumens of light at sea level on a clear day. A lumen is defined as the amount of light emitted from one candle that falls on 1 square foot, one foot from the source. So, here’s the deal. A 5000 lumen bulb one foot above a plant will provide the equivalent of 5000 candles of light. If you place the light closer to the plant you can maximize the amount of light the plant receives. I place my fixtures 4 inches above the plants and raise the fixtures as the plants grow in order to maintain this height. Here is the formula. Light intensity is calculated using the formula l = L/D2 or “light intensity equals initial lumens divided by distance squared.
If a plant is 4 inches (.33 feet) away from the light source, 9 times the initial lumens are available! Our 5000 lumen bulb is now providing close to 45000 lumens to the top of the plant! Note that T-5 lights give off very little heat so you can put them close to the plants without burning them.
How do you know if you are not providing enough light for your plants? According to www.guide-to-houseplants.com:
How much does it cost to run your 4 foot T-5 54 W light? I run my grow lights 16 hours per day. At 6 cents a kilowatt hour for 16 hours per day for 30 days works out to be $1.55 per month. So there you have it! Feel free to check my math.
I am also experimenting with growing wheat, barley, and oat grasses in trays without soil indoors under lights for use as animal fodder. How about that - fresh food for the critters in the dead of winter! Eventually, I intend to dedicate an entire unused room to growing edible plants. Why not? I will be able to harvest fresh pick-it-and-it food all year long.
This and related articles are available for viewing at www.PorterLearningCenter.weebly.com
www.PorterLearningCenter.weebly.com [email protected]
Three years ago, I started experimenting with growing lettuce, sunflower and broccoli greens, and several pepper varieties indoors under artificial lights. During the cold season (more than half of the year in North Idaho), my mountain cabin stays nice and toasty warm. I might as well take advantage of the warmth, add a few lights and grow food during the winter. If you are into gardening, why not set up to grow a few plants indoors? Why not have fresh pick-it-and-eat-it foods available all year.
Grow lights have been improved over the decade. T-5 HO (high output) Fluorescent lights are now available that provide increased light (measured in lumens) at lower cost per watt of power than standard fluorescents. The T stands for tube and the 5 stands for 5/8 of an inch in diameter. I now use 4 foot T-5 HO 54 watt lights for all of my indoor growing. One light will accommodate 2 standard 11“ x 22“ flats. They provide nearly 5000 lumens of light, the most bang for the buck for inexpensive grow systems. If you are just starting out with indoor growing, consider using the Jump Start 4 foot T-5 grow system available at the CO-OP in Sandpoint and can be purchased online. Note that these lights have a 6500k color temperature.
So, what is a 6500k color temperature? The K (Kelvin), in the context of lighting systems, is a measure of the color of a light source relative to a black body at a particular temperature. Well, that’s nice. What is important to us gardeners is that a color temperature of approximately 6000k is required to match "daylight". 2700k to 3500k bulbs provide higher output in the red spectrum of light which promotes flowering. 5000K to 6500k bulbs are full spectrum with much of the light in the blue spectrum which promote overall green plant growth. So if you are going to have only one bulb, it makes sense to use one that has a high color number between 5000k and 6500k. This year, I intend to purchase several 2 bulb T-5 light fixtures and experiment with mixing a 3000k and a 6500k bulb in each fixture for growing flowering plants.
Garden books will teach us that different plants require different amounts of light, but don’t let that stop you from trying to grow any plant you like indoors. As a point of reference, direct sunlight provides up to 100,000 lumens of light at sea level on a clear day. A lumen is defined as the amount of light emitted from one candle that falls on 1 square foot, one foot from the source. So, here’s the deal. A 5000 lumen bulb one foot above a plant will provide the equivalent of 5000 candles of light. If you place the light closer to the plant you can maximize the amount of light the plant receives. I place my fixtures 4 inches above the plants and raise the fixtures as the plants grow in order to maintain this height. Here is the formula. Light intensity is calculated using the formula l = L/D2 or “light intensity equals initial lumens divided by distance squared.
If a plant is 4 inches (.33 feet) away from the light source, 9 times the initial lumens are available! Our 5000 lumen bulb is now providing close to 45000 lumens to the top of the plant! Note that T-5 lights give off very little heat so you can put them close to the plants without burning them.
How do you know if you are not providing enough light for your plants? According to www.guide-to-houseplants.com:
- Growth is spindly, with long spaces between leaves
- New leaves are smaller than existing ones
- Lower leaves turn yellow and fall off
- No growth or slow growth.
How much does it cost to run your 4 foot T-5 54 W light? I run my grow lights 16 hours per day. At 6 cents a kilowatt hour for 16 hours per day for 30 days works out to be $1.55 per month. So there you have it! Feel free to check my math.
I am also experimenting with growing wheat, barley, and oat grasses in trays without soil indoors under lights for use as animal fodder. How about that - fresh food for the critters in the dead of winter! Eventually, I intend to dedicate an entire unused room to growing edible plants. Why not? I will be able to harvest fresh pick-it-and-it food all year long.
This and related articles are available for viewing at www.PorterLearningCenter.weebly.com