Question
I have been growing impatiens successfully in a small bed next to my porch for twenty years.  The area does not get a lot of sun and I water regularly.  About two weeks after planting this years plants ( they were doing well) I installed solar powered (LED) lighting around the perimeter of the flower bed.  Shortly after, they began dying.  Most are dead and the ones still there are not doing well.  Is it just a coincidence or is the 24 hour lighting killing the plants?

Answer
Believe it or not, you are right.  LED lights are sunlight as far as your plants are concerned.

I remember decades ago hearing about a desperate greenhouse owner who was about to lose his entire Christmas season Poinsettas business. He called in specialists, one after the other, to find out why this crop of plants had not formed their signature bracts.

Poinsettas are sensitive to day length.  They require total darkness for a certain number of hours, for a certain period of time.  Walk in and swicth on a light just once, and you break the cycle.  You're back to square one.

In the case of this Poinsetta grower, no one could figure out what was wrong. You know he was not the type to walk in and flip a switch at night to see how his plants were doing.  Then someone found the answer.

Across the street, a new business had opened.  There was a new, flashing neon sign right across the street from the greenhouse where these Poinsettas were growing.  These lumens that crept in made it impossible for all those Poisnettas to flower that Christmas.

Live and learn.

Now, I know an LED is not the same as a neon sign, or an incandescent bulb.  But the lumens are just as light-worthy.  Just look at some of the LED products that are being pitched to the green-thumb market:

www.htgsupply.com/Product-LED-Spotlight-Bulb-TriBand-Spectrum---ONE.asp.

http://www.led-grow-master.com/

http://www.growlightsupply.com/index.php?main_page=index&cPath=6_8

Why would your Impatiens die from LED lighting?

Look at these answers:

http://www.newton.dep.anl.gov/askasci/bot00/bot00333.htm

My favorite is Dr Anthony Brach, who writes: 'Most plants (C3) require time for respiration during dark hours. Some plants (CAM, e.g., cactus) actually carry on photosynthesis during the night to prevent water loss.'

Edward, what would it be like for you to always breathe IN and never breathe OUT?  What happens to people who don't sleep?  If you never put gas in your tank, does your car still run, and run, and run?

Those LED lights turn on magically at dusk, as the sun sets.  Your Impatiens never rest.  A man may work from sun to sun, but an Impatiens's work is never done, at your porch at least.

Pity, because those LED lights are great little gadgets.  They use little energy and really spruce up a patio.  Sir, you are going to have to make a choice.  Alternately, you can tuck your Impatiens in for the night, covering them with black plastic (Hefty begs work well) to make sure they are not disturbed by your LEDs.

A fascinating problem that I really enjoyed discussing this week.  Who knew?

Good luck, there,

L.I.G.