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How many hours a light a day?

I deemed the little light from my kitchen window wasn't giving adequate lighting.  So I got a twin 48" setup, a timer with 15 minute increments and two 90 CRI, 2200 Lumen lights.  These plants are getting expensive...I'm going to need more plants to bring my cost per plant down.

I'm wondering how many hours of day of light is optimal?  I'm considering using sunrise and sunset data from Wilimington to get a more natural lighting duration.
Weather.com Sunrise and Sunset Data

My question is, because my light setup is only say 90% that of sunlight, do I need a 11% longer duration to make up for it?  Is nature's sunlight duration optimal or do the plants do better with 13-18 hour days?  Anybody have any experience with this or can point me to an expert?
fwiw, i run my lights from about 6 am till 10 pm.

this is over a 55 gallon fish tank. lights are 4-4' "cool white" bulbs. i forget the specifics on the bulbs. the tank also has acrylic lids on it.

keep in mind, that when using flouresent lights, the light levels change with distance. the further away your plants are from the bulbs themselves, the less intense the light will be.

have you read the acticle on lighting in the terrarium forum yet? there's some really good info there!

Yes I read their lighting post.

I put the Weather sunrise and sunset data into a spreadsheet, created a spreadsheet with scheduled 15 minute increments of lighting. I extended roughly 11% and rounding to the next 15 minute interval since I do not have real sunlight. My calculations revealed between 11-16.25 hours durations to be used. I believe if you have artificial lighting that is further from sunlight, you will need even longer durations.

Oh well, graphs are neat
I would say that about 14 hours a day would be suffecient. I dont grow mine with artificial light so unfortunately I dont have any hard data to offer you on this. One thing to keep in mind is in the fall (like now) you need to start gradually cutting back the ammount of light you give them to trigger dormancy. I would start cutting back 15 mins a week untill you see the plants have produced their dormant leaves/traps. Then you can put them into the fridge or whatever you have planned for dormancy for them.

Good luck
I can do better than 15 minutes a week.

This is my duration time based off of day of the year.


At least that is based off of scientific data, I'm not sure if optimal growing conditions reflect nature's growing conditions.
I am looking over the chart of sunrise/ sunset times and it looks like you only lose about 1 or 2 mins a day naturally. I would try to mimic that as much as possible. So that would work out to approximately 15 mins a week. Any more than that would not be what they would get in nature. Would this have a negative effect on the plants? I don't know. But imo duplicating natural conditions as closely as possible is probably the best way to go.

While I have a more exact schedule to follow, on average it is roughly 12 minutes a week (although thats over the year). So 15 minutes a week is a good approximation. I opted to give the plants more artificial light to make up for the fact that it is not true sunlight.

I'm just pretending to be a botanist.