Author Topic: Grow Lights on Lemon Tree  (Read 721 times)

fifthsymphony

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Grow Lights on Lemon Tree
« on: December 10, 2022, 06:45:00 PM »
Hello from VA,

We've had this potted lemon tree for several years but decided for the first time to bring it in for the winter.  Previously wed just cover it with burlap and drag in into our shed.  Its managed to survive 3 winters here in northern VA even though we get plenty of weeks of well below freezing weather down in the teens and 20s often enough at night.  Likely, because of this, the tree has always looked a bit haggard and spindly - not very lush; it has six very slowly growing lemons.  In spring and summer, it sits in a good sunny location, but I think the cold winters have taken a toll.

This year we made the considerable effort of bringing it inside - about 3 weeks ago now - and to buy and put it under grow lamps.  I've been fussing with just where to put the lights, how far from the tree.  (I should note here that where the tree sits, in our basement, it gets very little natural light, almost negligible). 

I purchased two of these dual head grow lights from Amazon: "Grow Light with Stand, Lordem Full Spectrum LED Plant Light for Indoor Plants, 200W Dual Heads."
Here are the listed specs at Amazon:
Input Power: 60W
Lumen: 4500 lm
PF: >0.9
PPFD/1 Feet: 685μmol/m/s
Color Temperature: 4000K
(Beyond this, the manual simply says to keep the lights at least 9 inches away).

At first, I had the lights about 9 to 10 inches away from the top of the tree on one side, aiming down.  But I noticed what *appeared* to be sunburn on some leaves yellowing/ browning tips.  But from my research, this could also be caused by other things.  And oddly, some of that yellowing and even the browning tips occurred on leaves farther away from the lights.  (And the lumens from these lights drop off very quickly with distance).

Honestly, I think it just may take some time to get it dialed in.  I watered and fertilized it (first time it's ever been properly fertilized) with citrus fertilizer (Miracle-Gro Shake N Feed Citrus) a few days ago (it was finally dry down to about 3 inches into the soil after bringing it in).  Part of the problem is that the tree wasn't in great shape when we brought it in, and it took a bit of a shock in transition as well - a handful of leaves went yellow and dropped off.  It does appear to be perking up maybe most of the leaves are a light-green shade not awful looking, but not much deep green.  The tree did sprout 5 new buds down low at the rear and these have been exploding, really taking off one good, healthy sign.  But I'd love to get some advice about these lights.  So, there is a lot going on here: tree never really in great shape in first place/ survived several winters outside, shock of coming in from outside, now the grow lights, and fertilized for the first time (and because its slow release, it may take some time to take effect).

I was hoping to see or hear about other lime tree setups see how close others put their lamps of various wattages or lumens output.  I've moved the lights further away from the tree for now.  I have a light meter app (who knows how accurate).  And with the lights about 14 inches away, I measure about 9K lx at the closest leaves to *each* head.  But I have another dual-head lamp that sits by a jade box next to the lemon tree.  And one of its heads aims directly toward the lemon tree as well (but about 20 inches away) Im only reading about 3K Lx from it at the tree but still, basically I have three lights aimed at the tree, all told.  But the overall avg. covering the entire tree is prob. somewhere around 2K lx or less.  (For what it's worth, the jade plants don't seem to mind the lights being closer - in fact, seem to like it best with the lights about 9 or 10 inches away).

Is it even possible to burn this plant with these lights unless they are right up against the plant?  The lights themselves put off very little heat - you can put your hand right up on the face of the bulbs and leave it there, i.e., warm to the touch, but never hot.

Thank you very much in advance for reading and any advice, Gary in VA

(The pics:  In the first pic, you can see the current lamp placement with distances.  And in the second pic, a full shot of the tree with an arrow pointing to the new buds and another arrow pointing to a branch that broke at the bottom that I taped up thus the yellowing leaves on that branch.  It has a lemon at the end, and I hope there was enough skin left on the branch to heal up there appeared to be, but time will tell. 





1rainman

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Re: Grow Lights on Lemon Tree
« Reply #1 on: December 10, 2022, 09:03:14 PM »
My dwarf meyer lemon was a thick bush and maxes out at six feet tall. I put it outside for summer and brought it in when temps go below freezing. It did really well and got lemons. It might be too big of a tree in a small pot which will cause it to grow weird the dwarf meyer is the smallest and best suited for containers.

They can go in shock switching from natural light to artificial and vice versa. I tried to keep mine near a window even though I used artificial light. Every thing did better outside in the summer than inside in winter but I kept them healthy enough in winter so that they were healthy. Seems to be a lot more spider mites or bug problems indoors too.

The plant looks fairly healthy in the photos. Usually long skinny growth means not enough light but you said it was out doors.

I use a full spectrum florescent bulb and you can put them a few inches from the plant and not burn it. Then mix it up with a sunlight florescent made for reptiles. That one needs to get a smaller dose further away but seems to help mixing different bulbs with slightly different spectrum. Led I don't know if it will burn them. I don't give them too many hours of light in the winter it seems to stress the outdoor plants. I guess they expect shorter days in winter I don't know but I do 12 hours max or sometimes they stress. It's really finicky with artificial light. That's why I try to rely on a window and just use artificial light to supplement it.

Of course if you never put the plant outside it will eventually get used to the artificial light. But just taking it in for the winter there's natural rythems and cycles does best without a lot of artificial light. 8-12 hours up high not super close. One leaf might get a lot more light than another and confuse it so have to cover the whole plant in about the same light hence moving the light source up. Though mirrors and aluminum foil can be put around it to reflect more of the light on the plant.

And I don't fertilize when indoors for the winter. I just try to keep it healthy then in spring when it goes outside fertilize and it takes off.

I did have tiny almost invisible slugs sucking sap without me knowing and the plant was sad looking at one time. I sprayed the whole plant with neem oil and the dirt a few different times and got rid of them but I took it outside so rain and hose can wash the oil off don't want it sitting on the plant too long. Takes several rains to wash off as it is. So could be insects.

vnomonee

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Re: Grow Lights on Lemon Tree
« Reply #2 on: December 10, 2022, 09:07:07 PM »
LEDs should not burn plants unless the diodes are physically touching the leaves. The only concern I have is that your plant looks like its potted deeply, should not have the trunk buried that high up. Biggest issues you might experience indoors are overwatering and spider mites/other pests.

fifthsymphony

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Re: Grow Lights on Lemon Tree
« Reply #3 on: December 11, 2022, 11:27:59 AM »
Thanks guys!  Your comments and notes help.  I did think maybe it was some sort of insect I couldn't see so I gave it a spray with Sevin Fruit, just to be safe.
I wish I could get it closer to natural/ sun light while inside, but I just don't have a spot for it.  It sits in the back corner of the basement across the room from the sliding glass door (facing east and with a porch) so very little sunlight reaches the plant (and no direct sunlight at all).  It has to be just the grow lamps for the winter.
I fear that leaving it outside for the last three winters just took a serious toll on the tree and it's going to take some time for it to recover and adjust to the grow lights. 
I forgot to say, I've been leaving the lights on for 12 hrs a day.  I think I will just leave it alone for another month and reassess.  At that point, I should hopefully know more and either back the lights further away, cut down the time, or even bring them in closer.   We'll see.  And I should give the fertilizer time to do its thing too.
Thanks again, Gary

Vegan Potato Man

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Re: Grow Lights on Lemon Tree
« Reply #4 on: December 11, 2022, 02:19:42 PM »
Lux is intended to measure visible light to the human eye. Horticultural lighting needs to be measured with a PAR (photosynthetically active radiation) meter that measures usable light for the plants. With a PAR meter you can calculate PPFD (Photosynthetic Photon Flux density) as well as Daily light integral.

That said, I'd imagine a PAR meter is likely outside what you'd like to spend. They usually run 400-500 bucks for the basic ones.

Otherwise I'd say your plant looks healthy and will probably appreciate being inside more than out in the shed under burlap.

Best of luck!

fifthsymphony

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Re: Grow Lights on Lemon Tree
« Reply #5 on: December 11, 2022, 04:41:53 PM »
Yeah, thanks Vegan Potato Man,

I've been reading about those other important measurements in my research and your post finally gave me impetus to look for a PAR meter.  I found the "Photone" app for my android phone.  Has lots of great reviews, so gave it a shot.  It measures PAR, PPFD, LU and KELVIN. 

Even if it's not terribly accurate, it gives me a notion of what's going on and basically, there is no way in the world I can put too much light on my lemon tree with these grow lights. 

The leaves directly in front of each head and about 3 inches away might get 300 PAR and 10 PPFD (12 hrs), but just that small area because it drops off dramatically to the side with distance.  At center of canopy I measure about 150 PAR and 6 PPFD.

So, I'm fairly convinced that I can place these lights closer and not worry about burning the plant.  So, I've done just that - snugged the two main heads for the lemon tree about 4 - 5 inches away and the shared head that also points at the tree, about 10 inches away.

From what I've read, lemon trees like anywhere from 300 - 600 PAR and 21- 28 PPFD.  If I extend my light on time to 18 hrs, I can get close to 20 PPFD (but just in those areas directly in front of the lights and about 4 inches away.  Center of canopy, significantly less.

So, my plan is to keep the lights closer - 4 to 5 inches away on each side and the other light (shared with the jade) 10 inches away and extend to 18 hrs for a few weeks and see what happens.

Thanks again everyone. Gary

1rainman

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Re: Grow Lights on Lemon Tree
« Reply #6 on: December 11, 2022, 06:23:02 PM »
It's not as much that a plant likes certain light. It just adapts. If you take an indoor plant and put it outside you risk sunburn until it's used to the sun. Then going in from outside is an adjustment. It's just like a human if you work in an office every day then spend a day at the beach you get burned. If you spend every day at the beach and it doesn't bother you. Though the light does need to be usable the right spectrum and a certain minimum. The plant will adapt to different kinds of light it's mainly the switch to a new one which will cause some stress but not a lot in most cases.

Ognin525

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Re: Grow Lights on Lemon Tree
« Reply #7 on: December 12, 2022, 09:32:52 PM »
I agree with rainman just full spectum leds is what i run in my set up. Iv never measured any light intensity or anything. Iv fruited a bunch of different things with them just fine including citrus. With the low wattage thoes lights are you really shouldnt see burn iv only seen burn on 150watt+ led panels when they get about 2 inches away(running 70watt bars now bc of that).  I keep them 4-8 inches away on larger plants and 12" from seelings, if they are to far 16"+ they start to get lanky (these are solid nums for my set up might need slight tweeking for others). Your on the right path for sure good work!!!! My first year indoors was a mess haha even now on year 4 i still run into issues but thats why i love growing indoors its always interesting and you learn ALOT plus no chipmunks steal my fruits haha.
Bill

fifthsymphony

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Re: Grow Lights on Lemon Tree
« Reply #8 on: December 13, 2022, 04:21:38 PM »
Thanks Ognin, 

I've come to the same conclusion over the last several days, doing more research and trying to understand what a lemon tree needs and what these lights give me.  I moved the jade to another location so that I can dedicate all four of these grow lights to the lemon tree alone.

Your post gives me more confidence I'm doing the right thing.  These lights arent going to burn the leaves in fact, even with all four directed at the tree, it doesnt come close to what it ideally requires.  But Im hoping its enough to get it growing nicely.

Ive attached a few pics of the leaves - what I was talking about in my original post (should have included them there).  Whatever is happening, its not from the heat of these lights.  Weve had very wet summers and this plant probably hasnt had a good opportunity to dry out in ages (except for those three winters in the shed, where it got nothing at all no sun, no water, and well-below freezing temps for weeks on end).  On top of that, its been lacking proper nutrients as well.  It took three weeks for it to dry out enough for me to water it after bringing it in (and even then, it probably could have gone another week, really).  But that gave me an opportunity to get the fertilizer in there for the first time.  I'm anxious to water it again, to get those nutrients flowing (the slow-release Miracle-Gro Citrus), esp. the all-important magnesium. 

I've also included a pic of the new light setup.  All I can do now is wait and watch and hope for the best. 

And per vnomonees advice, I cleared away some of the soil from the base of the tree it does look like it was potted too deeply.

Thanks again everyone.  Ill keep you posted, Gary







martweb

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Re: Grow Lights on Lemon Tree
« Reply #9 on: December 14, 2022, 01:09:16 AM »
I really like using MARS HYDRO TS1000.

poncirsguy

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Re: Grow Lights on Lemon Tree
« Reply #10 on: December 14, 2022, 11:55:29 AM »
I have 5 LED lights, all 9 watts, on my Meiwa kumquat tree with Flying dragon rootstock.
  New growth









Lots of new growth with lights shining from different directions to reach deep into tree's inner leaves  No Blocking shadows and each bulb bought on discount from $1 to $2.25  Tree has 2 LED daylight and 3 LED 3100K bulbs with a window on the south side.

fifthsymphony

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Re: Grow Lights on Lemon Tree
« Reply #11 on: December 14, 2022, 12:55:45 PM »
That looks real nice, poncirsguy.  Unfortunately, with my location, I have no natural light - or so little, it's not measurable.
But I have to say, after just a few days with all four lights on the tree, I swear I see a difference - the leaves seem to be perking up.  And those few buds are blooming fast and well.  My hope is that the rest of the tree catches up - that it gets more lush, more buds, more lemons... with time.

Tropicaltoba

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Re: Grow Lights on Lemon Tree
« Reply #12 on: January 17, 2023, 07:50:49 PM »
New to the forum but been growing for a bit. Another thing to check is the leaf temp under the leds. A cheap IR thermometer can tell u a lot. With low indoor humidity (transpiration shuts down) and air movement youd be surprised how hot the leaves get. Also the leds themselves get crazy hot, I made some from scratch and despite an (supposedly) adequate aluminum heat sink with fins, if there wasnt a fan blowing over them, they got to 90c (approx 200f).

poncirsguy

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Re: Grow Lights on Lemon Tree
« Reply #13 on: January 17, 2023, 11:04:07 PM »
LED's put out about 84% heat and only 16% light.  They are lousy at producing light but we just don't have the technology to do any better.

 

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