I have heard a lot of things about how much sun citrus really need but does someone really know? How much do they need to flower and fruit not just live? I have heard my south east windows are good enough. The windows are bright but only cover about 1/4 to 1/3 or the tree for direct sunlight.

I have pictures on a posting from a couple of days ago.

Since you live in Saint George, UT you can during the summer move them outside and they well get all the sun they need. Though like someone mentioned in one of your other post you should shade the pots so the roots keep cool. St. George can get mighty hot in the summer, and hotter still in a black plastic pot.

Then in winter bring them in to your window.

I live close to st. george, about 45 min but my elevation is about 3,700 feet higher. unfourtunatly i do not have the same good weather. It is like northern utah weather here. I am actually rated one zone lower than northern utah because I am just a little bit higher. I do plan on putting them out later in the summer but it is just to cold at night still. Is there a different pot I should put my tree in besides those black pots that they came in?
Thank you to everyone for your help

I'm in a similar area, high desert (6000'), with hot, dry summers. I got my first citrus (a couple Kaffir limes and Meyer lemons) in the winter of 2007. I babied them, and had them under fluorescent lights through the winter. They did great, with lots of lush, new growth.

I thought they'd do great outside in summer, but the intense UV, heat, low humidity, and wind was too much, too soon. They all lost a lot of leaves and just didn't seem to thrive.

This year I plan to keep them on the northeast side of my deck, under an awning, where they'll get early morning sunlight, and be a lot more protected from the intense mid-day and afternoon sun, wind, and all of that.

As for pots, I put mine in light colored plastic containers that I had drilled out for better drainage. But I'm thinking the location is more important than pot color.

I'm new to citrus, but those are my experiences, fwiw. Good luck!

Would there be a difference between potted and grown planted trees? If citruses can grow in hot dry Phoenix, Arizona then why would it matter about UV and dry heat? As long as they get plenty of water to keep the plant hydrated.

The wind could be a problem, increasing evaporation beyond the plants ability to replenish.

Instead of how much sun needed, we can try to read up on the effect of moderate shade:

link

Joereal do you know where i can read about the effects of moderate shade?
My trees get about 3-4 hours of direct sunlight but it only hits 1/3 of the tree even though it's a south/east window. I make sure that I rotate the trees but its a weird window. But I'm trying to decide if it needs a grow light also. Thankyou for everyones responses. ( :

Joereal sorry my computer is weird after I posted that question the link you put finally showed up.

I believe that Millet posted fact about citrus that said they reach their maximum photosynthetic rate at a light intensity of about 650 (micromoles/meter sq/second)-- that works out to be less than 1/3 of the maximum solar intensity that we get here in NW Florida. Although citrus trees can tolerate higher intensities, these higher intensities can do damage to the photosynthetic apparatus of the leaves and does not provide any additional benefits. Citrus trees evolved as an understory tree and are adapted to partial shade.

What does matter is time or duration of exposure--longer exposure does produce more growth.

I have for several years now been growing some seedlings under a shade cloth --they have done well. It even helps prevent winter leaf drop for container citrus. All of my inground trees get less that full sun, most less than 1/2 full sun.

> micromoles/meter sq/second
I doubt about the micromole.

When Skeet is talking about 650 (micromoles/meter sq/second)-- he is using a different terminology to state the phrase: ---- " 650 PAR" meaning Photosynthetically Active Radiation, often abbreviated PAR. Which designates the spectral range of solar light from 400 to 700 nanometers.

Millet (1,364-) Everybody is Somebody