Travis, sounds like a good science experiment :) We all have streetlights and other ambient lights in and around our homes and plants that I don't think impact them unless the lights are significantly bright. Plants are such great adaptive survivors, during summer further north in Canada and Alaska, they get 24hr sun and and have prodigious growth, so the light cycles are something that plants can adjust to for sure,

Can you putting them in full sun, but under a shade cloth or filtering structure? I've got a friend who has a in ground orange tree in Vegas which he gets huge harvests from and primarily just waters it uses a shade cloth over it if it's multi-day 100+.

That's a good point about our northern friends Ken, I hadn't thought about that. I'm encouraged by your optimism :)

Neither of my trees are fruiting right now (both are young, the lemon had several fruit which were all dropped after a few days of triple digit temps) so I'm not as concerned with the time spent in shade this season, I mostly want to keep them alive until the fall respite. It's also not a deep shade, they are about 1' from open sky. But I am very open to creating a filtering structure for the future. The heat came upon me so quickly this year and I didn't know how my trees would react so I wasn't prepared. The front porch was the best I could do at the time. The grapefruit was tolerating it better and stayed out in full sun longer but just started to show signs of sunburn so it got moved to the porch too. We will get months of uninterrupted daily highs in the triple digits, so I'd like whatever I build to be somewhat stable (i.e., something that can stay put for a stretch). Perhaps a PVC frame with shade cloth, or something like that.

Interesting question.

https://crec.ifas.ufl.edu/extension/trade_journals/2010/2010_Nov_supplemental_lighting.pdf

https://www.extension.purdue.edu/extmedia/FNR/FNR-FAQ-17.pdf

http://cescos.fau.edu/observatory/lightpol-Plants.html

Thank you for the resources, I'll drive into them. I read one such study which suggested trees have different levels of sensitivity to light pollution, but citrus varieties were not included in their tables, so ??.

there is no problem at all.

That's what I like to hear! 😃

Travis spent an hour and couldn't find a specific answer. Here is another piece of the puzzle. https://homeguides.sfgate.com/24hour-light-schedule-bad-plants-95954.html

"Because dark reactions do not require the absence of light, plants will remain healthy when exposed to light 24 hours a day. There are some plants, however, that will survive but not thrive without darkness."

I think because landscape lights are not intense they will have minimal affect.

Thanks Lemon Lime Orange! That was really helpful!

Shade

I can provide an answer. Giving them LED light will not negatively impact them at all. The only issue to be concerned about is whether they are getting enough light.

And keep in mind that in desert conditions, very often less light is much better overall for the plants than excessive sun. Plants almost always will do better in desert conditions under a tarp that shades out 60% of the light than no shade tarp at all.

However, when you're talking about near total shade, that can be a different story, and I would bet your LED lights are putting off far less light than you think. Everything looks brighter at night, and it's easier to overestimate how much light there is. If you're getting morning sun, that should be enough. And the LED lights could only help, but likely are not actually helping that much, less than you think.

You've got a lovely front yard LLO, all your trees look very happy!

Thanks for the clarification socal. I don't expect the LEDs are helping at all, I was concerned they were harmful by not letting the trees "sleep. " Your explanation cleared that up.

Hi Travis, is there a product in Arizona to spray on leaves to prevent sunburn? I see they paint the trunks in Southern States. I can't buy tree white wash in Canada but I can import it. I see recipes on the internet mixing half outdoor latex and half water. Not sure if the chemicals in big box store outdoor latex would negatively effect tree? Thanks.

Banana boat SPF 45 dilute and spray, Or

I'm not aware of anything that can go on leaves; if your leaves keep getting sunburned then I would recommend increasing the shade. Some sunburn on your leaves is okay but I try and minimize it. For the trunks I used 50/50 latex and water, however you do NOT want outdoor latex. Outdoor latex has chemicals to resist rot and mildew and that will be harmful for your tree. You want indoor latex. I got mine at my local big box store. I just looked for the simplest interior latex I could find (which was also the cheapest). I avoided the paint + primer in one formulations--I don't know if that will make a difference or not. Just a small pint of basic interior latex, I think cost less than $5. On previous trees I also painted some branches because I had lost a lot of leaves so there wasn't much protection. Your trees look good, I'm just sharing that because I had questions about whether the paint on branches would interfere with bud development, etc. Turns out it's fine.

Hi Travis. Thanks for the information. I have never found anything to block sun on leaves either. I did come across an article from Arizona that recommended using burlap as a shade cloth in a heatwave. I am still still an umbrella and the plants seem to like it. The plants face south. As the sun passes over they are getting a fair amount of shade. Not sure whether they are getting to much shade now.

They look happy to me! As long as they are getting several hours in the morning. It's probably too much hassle, but ideal would be an umbrella that allowed filtered light through :)

Travis, the clay I mentioned in your sunburn thread is commonly used to protect plants from sunburn (as well as certain insects). It's sprayed all over the plants (topside if only sun protection), or all over if used for pests. The downside is that is washes of easily. For dry sunny areas, it's particularly effective.

Hi Ken, can you share a picture of the packaging of the Kaolin Clay. Never heard of it before. Sounds like what I have been looking for. Can it be bought as an aerosol or do you make your own mixture with water? A quick Google and it says it also increase photosynthesis. Looks interesting. Thanks for the tip.

There are many variants of kaolin clay that are sold. smaller packages tend to be used for human use - cosmetics I think, but would suffice for hobby gardeners. One of the "u-pick" organic peach orchards in SC that I occasionally visit uses it for both anti worm primarily. I had to ask the farmer why the peaches and the trees looked like they had been covered in off white. He told me that he has some more temperate fruit trees that he uses to help moderate high temps. They have big bags (like 40-50lbs) that they put in a tractor sprayer of hundreds of gallons of water.

Unfortunately, I don't have a package to share a photo. I got a few pounds from the farmer a few years ago, he gave me a few pounds in grocery bag. I've found it useful to "hide" ripening fruit from birds and squirrels - as they look for color and a heavy coating camouflages berries well - but they'll smell the ripe fruit if they get close, but it helps save me some berries and cherries.

Thanks for the reminder Ken. I did a little more research and it sounds like it can be a very helpful product. Lowers leaf temps, assists in transpiration, prevents sunburn and deters pests. I could use all of those things :) The main product that most research papers mention is Surround WP and they only come in 25-lb bags, way too big for my needs. I'll see if I can find some sourced locally in smaller quantities.

https://www.arbico-organics.com/product/surround-wp-crop-protectant-omri-listed-kaolin-clay/natural-organic-plant-disease-control

One Green World lists a 5 and 25 lb size but both show OOS

Lemon Lime Orange, what kind of cacti are you growing outside in 6b? Do you bring them in over winter? They look really healthy.

LLO, I've been watching citrus videos on YouTube and the guy from IV Organics will dilute their 3-in-1 plant guard (whitewash paint that's supposed to be better than using latex) and then spray it on all the leaves.