riverofwind
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Artificial Lighting For Various Plants

Hi I have an indoor garden of mostly cacti and succulents. I'm looking to find an optimal lighting cycle for my 4 T5 fluorescent tube lighting fixture (high output 54 W full spectrum agrobrite hydrofarm). This is complicated by my sleeping patterns; I have my computer desk light on from 8:20 PM or so until 11:00 PM. Also I don't open the blinds until 11:30 AM. I have been trying to give my plants more darkness because of my computer desk light by not turning on the grow light until it is 8:30 AM even though the sun usually comes up earlier. So currently the lights run from 8:30 AM to 8:30 PM. What would be an optimal lighting cycle given these conditions? Also should I change the cycle depending on the season and natural light cycles? I'd like the plants to go into dormancy in the winter and come out of dormancy in the spring and summer. I live in San Francisco area in California. And is it best to have the lights on the same period as the natural sunlight or is there a better way?
Thanks!

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applestar
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I've moved this topic to Cactus and Succulents forum since you said that's what you mostly have and their light needs should probably take precedence. Unfortunately My experience with these plants is limited. My few live on benign neglect on mostly available sunlight from SE windows, though my Thanksgiving "cacti" and some of the aloe get additional light from supplemental daylight CFL which is turned on at dawn and off around 11pm.

But what are your other plants?

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rainbowgardener
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I can't answer all that, sounds complicated. But re: "And is it best to have the lights on the same period as the natural sunlight or is there a better way?" Artificial lighting is so much less light intensity than sunlight, that usually to make up for that, you have them on a longer period of time. For seed starting and for my pots that I bring in for the winter, I usually have lights on 16 hrs a day.

I think you are complicating it more than you need to. If your plants are not right next to your computer desk, then the desk light is going to make no difference one way or the other. Light intensity varies by the inverse square of the distance. So if you have a light that is four inches away and you move it to eight inches (twice as far), the plants are then getting one quarter the light. If you move it to 16" (four times as far), the plants are getting 1/16 the light or about 6%. So you can see, lights that are more that a foot or so away from the plant are contributing very little.

riverofwind
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@applestar I also have a couple ferns and club moss and a pony tail palm but they don't need as much light and sit to the side of the lighting fixture. If going from dawn to 11 pm do you hold that cycle year round without worrying about if the plants will enter dormancy? Does it give enough darkness to let the plants "sleep"?

@rainbowgardener The desk light is 6+ feet from the side of the fixture. I can also block some of it with a piece of cardboard. Will the plants "sleep" through that? Also if I run the fluorescents from dawn to 11 pm like applestar the desk light doesn't even matter since it goes off at 11 pm.

What's an optimal light cycle with my 4 T5s (20,000 lumens total over about 6-8 square feet)? What time to turn on and what time to turn off? I want to make sure they get enough 'sleep'. Can I hold the same cycle year round or should I modify it? If so how to modify?
Thanks again

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applestar
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I expect warm-climate plants like cacti are more used to the shorter day length year-round -- 12/12 along the equator. My dawn to 11pm cycle follows the sunrise/first light -- which is as early as 5am in the longest days of the summer and as late as nearly 8am in the depth of the winter, so that transition probably helps.

But more so to emulate dormant period, I believe you are better off controlling the moisture levels and temperature.

My succulents are on the windowsill or on a table just below the windowsill which can get really cold during the winter months -- when it;s coldest (negative single digits °F) condensation on the inside of the double, double windows can freeze at the bottom, so I do move the ones that are frost sensitive away from the window glass. They are nearly dried out -- not quite.

For maximum brightness -- for blooming, I position plants about 4 inches from T5 tubes. I use 6500K daylights. Thanksgiving cactus is the one that is most sensitive to day length for blooming and I put those in a room without artificial supplementation until they set flowerbuds.

riverofwind
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Re controlling moisture levels and temperature - my plants are from 0.5-4 feet from the window. I leave the window open a crack from 12:00 PM to 12:30 AM. Should that suffice to stimulate dormancy?

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Gary350
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I don't think you can force plants to do something unnatural like go into dormancy.

When I lived in Phoenix BIG SKY country the summer Sun started coming up at 5:00am and it was light at 5:15am. It was dark at 8:30pm. No clouds in the sky, no trees, no shade, full sun all day really was full sun for 14 1/2 hours.

Cactus can tolerate the worse weather conditions possible but they thrive at 70 degrees and 4 hours of cool early morning full sun per day. My cactus garden was outside house and fence provided shade for 10 1/2 hours.

My Succulents were outside in full shade all day, no direct sunlight all day. They did best 70 to 85 degrees. Irrigation gave they 10 minutes of water once every day.

Cactus and Succulents grow good in Arizona winter when it is 70 to 75 degrees every day and 30 to 35 every night most of the winter.

I had plants in pots and in the soil too. Plants it pots were very hard to grow they do not like uneven soil moisture, dry, wet, dry, wet, over and over every day from being watered once a day. My plants kept dying in flower pots so I moved them all to the soil then they grew good, I hardly every needed to do anything to them in the soil. Plants multiplied very fast too fast to keep up with so I ran ads on Craigslist, FREE plants come dig them up your self. Most people only wanted a few plants but some people hauled plants away by the truck load.

If you don't give your plants sunlight cactus will turn yellow and die, succulent will turn white and die.

Cactus and Succulents both grow best in winter in cooler weather. I don't think you can make these plants go dormant in winter outside that is when they grow best. These plants are basically dormant in summer when it is 114 degrees they do not grow in extreme hot weather they survive until weather cools down in the 70s. Best thing you can do for your plants is keep them inside air conditioned at 70 degrees. If you want them to go dormant put them in an incubator at 114 degrees but they still need sunlight.



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