Grow lights often need to be closer to plants than you’d think.
Mariya Borisova
Grow lights or supplemental lighting sources are useful for starting seedlings and giving houseplants a boost.
This is especially true when natural light in your home isn’t very bright.
Credit:Mariya Borisova
But ifyour grow lightis too far away from your plants, it won’t be doing much good.
Why Light Distance Matters
Like sound, light intensity dissipates or gets weaker farther from the source.
And it does that rapidly.
Light intensity decreases as a mathematical function called the inverse square law.
You don’t need to know the equation, but you do want to know how it works.
But doubling the distance means the light received by the plant is only one-quarter as strong.
The bottom line to remember: As the distance increases, the light intensity dropssignificantly.
How Much Light Do Plants Need?
The old-school way is to let the plant tell us.
Flowering houseplants such as African violets that aren’t receiving enough light may also fail to bloom.
Light meters designed for plants are not the same as those for photography.
They measure only light of the right frequency to be useful for photosynthesis.
This light is called photosynthetically active radiation, or PAR.
They’re also not very available anymore.
Fluorescent Lights
Fluorescent lighting can be used as grow lighting, but it has limitations.
Forseed-startingand growing young veggie and flower plants, fluorescent lights need to be 2-4 inches above the leaves.
LED Lights
LED lighting is more powerful, even though it uses less electricity.
For starting young plants, 8-12 inches above the leaves is a good distance.
Houseplants can sometimes be 2-4 feet away, allowing you to group several plants under one light source.
Of course, higher-powered LED fixtures can be farther away than low-powered lights.
Industrial strength lights are available to purchase, although they are more expensive.
And watch for symptoms of too much or too little light.
Look for a mounting system that easily adjusts for height, allowing you to fine-tune thelight for your plants.
Putting the lights on a timer is the last key to providing the right light for your plants.
