Series 2, pg 2 – brightness, color, intensity

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This series will help you have happy, healthy plants to enjoy all year round in hour home.  Series #1 began with providing the proper growing medium and Series #2 will focus on the different things to balance that will give your plants the best lighting conditions in your home.

by Mary Sue

 Let’s talk light… pg 2

          Time to find your balance

3 things – brightness and intensity, duration, color

Now that you know something about your plant and the natural light in your home from page 1 you can find the location your plant will need to thrive in your home by balancing these 3 things.

Brightness and intensity

This is the amount of light you supply for your plant for photosynthesis, fruiting, and flowering.  Humans and plants ‘see/use’ light differently.  Light for humans is measured in lumens and light for plants in micromoles.  For the home gardener reading packaging at the store you will most likely look for lumens.  More lumens does not directly translate to more useable light for your plants but it is a good indication for you.

A low light houseplant may survive with 500 lumens and prefer 1500 but a high needs houseplant will survive with 1600 (for a short time, winter months) and prefer 5000-8000 lumens.  The closer you place the bulb to the plant the more intense the light will be.

A low light plant may survive with 500-800 micromoles and prefer 1500 but a high needs plant will survive with 1600 but prefer 2000 micromoles. A T5 high-output fluorescent will give 400mm, a cloudy spring day 500-800, and a clear spring day 1500-2000 micromoles.


Once again you should know your plants natural habitat.  A flowering plant like an African violet will need the light to be closer and on for more time than a philodendron which grows well in shade.  You must also be careful of the heat given off by the bulb(s) you use.  Some, incandescent and HID bulbs, are very hot and will burn a plant if placed too close.  Fluorescent and LED are much cooler and can be placed closer.  More about long day and short day plants here.


The color spectrum (CCT, or correlated color temperature) is measured using the Kelvin scale.  You will see these numbers also on the packaging of bulbs you purchase.  Plants need both red and blue light which are at opposite ends of the spectrum so it is best to provide both.  A “warm” – more yellow/red light will be labeled from 1000K to 5000K with 2700K being common.  Plants use this light to promote growth and flowering/fruiting.  A “cool” – blueish appearance will be labeled from 5000K to 10000K+ with 5000-6500K being common.  Plants use this light to keep the foliage compact, a nice green vegetation.  Plants considered to have high light needs should get plenty of blue light.

PAR – photosynthetically active radiation – will be on some fixture and bulb packaging and is a measure of the wavelength needed for photosynthesis.  Plants need 400nm-700nm for maximum growth and 450nm when at the seeding stage and 650nm at the flowering stage and are some good starting points to look for.

On to page 3 for light choices.





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