Question
I have four orchids - 3 phalenopsis and 1 dendrobium under 2 grow lights which are both 24 inches long, 600 lumens and color temperature of 2700k a piece.  The fixture is timed for 12 hours of light exposure a day from 5:55 p.m. to 5:55 a.m.  I timed it at night so I am home in case something happens such as a fire due to the light fixture.  

I have had all four orchids under these lights for about seven months.  Not one orchid plant has bloomed.   Two of the orchids - phalenopsis - resided in a filtered south window, all year long, prior to the light fixture where they reside now and both bloomed wonderfully.  The other two have only been under the light fixture.  I am wondering, could it be I screwed up the timed lighting from natural day light and natural night sleep to the opposite - light fixture on from 5:55 p.m. to 5:55 a.m. - sleep or night being 5:55 a.m. to 5:55 p.m.?  But then why are the other phal and dendro not blooming, they have only been under artificial light since I purchased them?  

I water all every week - early morn - with a 19.31.17 orchid food.  Maybe it's the food now that all are under artificial light.  All are green and look healthy - the leaves are growing like crazy.  Any suggestions would be so much appreciated!

Thank you so much.

Molly

Answer
Hello Molly,

Sorry to hear your orchids are not blooming for you.  

You already have the solution in mind, turning off the lights at night and moving them back to the window.  Orchids need a period of darkness in order to grow and bloom, keeping them under lights all night is depriving them of this.  

You didn't mention where you live but you mentioned having grown the phalaenopsis in a south window, place them near it again so they will receive natural sunlight.  A word of caution if you live where the sun is very hot (such as the south), as hot sunlight can cause sunburn of the leaves.  A sheer curtain can help reduce the impact of the sun or you can try placing them off to the side of the window so they are in a semi-shaded area in the afternoon.  The dendrobium can withstand a little more sunlight than the phals, enough where the leaves are a light to medium green color.  Phal. leaves should be a medium to dark green color, if the leaf edges start to show red that would indicate it is getting a bit too much sunlight.  

While the 19-31-17 orchid food is fine, it may be better to use one that is more balanced where the 3 numbers are closer.  The food you are using encourages new growth at the expense of flowers, although your orchids may eventually produce blooms but it won't be very regular.  Also, most orchids produce blooms once a year, usually from late winter to spring.  To promote blooming, it may help to expose the orchids to night temperatures around 55 F for 2 to 3 weeks in the fall.

Hope this helps.  Good luck and good growing.

Jim Kawasaki
San Jose, Ca.