Daily light Integral (DLI) for Tropicals

groffralph

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Any suggestions on the DLI for Brazilian Raintree's and Jabotica? (12hrs daily)
 

Cmd5235

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I put my BRTs, ficus, serissa, dwarf pomegranate, and mimosa under 14 hours a day of light. No problems here
 

groffralph

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I'm sorry I wasn't referring the number of hours. The Daily Light Integral (DLI) is a measure of the aggregate amount of PAR light that a surface receives over the course of a day. It is a very useful metric to determine if a particular location receives sufficient amounts of light for plants to grow well.

If you have a Par Meter you can determine how far away your grow light need to be using this equation.
 

Tums

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You could use a map as a benchmark (as in if you were to live in a region where you could grow a tropical outdoors, what DLI could you expect there?). https://news.clemson.edu/new-national-light-maps-help-greenhouse-growers-manage-plant-growth/

But it sounds very difficult to match tropical sun in output especially if you're only doing 12 hours. For overwintering my tropicals/cacti/succulents, I think 25-30 is OK. Looking at the map I linked, the winter levels for Florida are around 25-30 anyway.
 

ShadyStump

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I'll have to take a measurement in the morning if you want any specific numbers, but my tropicals are in a north facing window with supplemental lighting that goes on when when I wake up in the morning, and off when I go to bed. An average of at least 14 hours a day. On some levels of the shelves I use it's mostly dark the entire time. Doesn't seem to bother my ficus, but my natal plum has gotten some very long internodes on the newest growth. I have several peppers, all capsicum annum, that slow way down indoors under these conditions, but are still quite healthy. They do tend to have MUCH lighter growth on the interior and lower branches, though.
Don't think I've ever seen a DLI greater than 30s at any time of day, but mostly much lower. This situation seems to keep them all alive just fine, but certainly not thriving optimally.
 

ShadyStump

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Thought I would clarify one or two things.

When I mentioned that my natal plum was getting long internodes this happened in the first couple weeks of it being indoors. After that the reduction in light triggers a quasi dormancy and the tree just stops for the winter.
Same thing happened to my bay laurel last year, but this year I avoided that by letting it stay outside in nighttime temps in the low 40s in order trigger that quasi dormancy via temperature.

Also, I'm on very limited means, so my supplemental lighting is very spotty. One plant might be getting a DLI of 25 while the one next to it gets single digits on a good day. I routinely move them around however their size might accommodate it.
 

Glaucus

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If you compare with other tropical plants that have a known DLI, like 30 to 40 mol/m2/day for peppers and 40 to 50 for cannabis, maybe 25 to 30 would be ideal for these tropicals.
There is a big 'however' though. Many tropicals are shade growing. Those become our house plants. Then they could be fine with 5 to 10.

You don't need to do your DLI in 12 hours just because it is a tropical, btw.
Giving them 600 umol/s/m2 for 14 hours seems reasonable.
 

LittleDingus

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Any suggestions on the DLI for Brazilian Raintree's and Jabotica? (12hrs daily)

You don't mention if under lights or natural lighting...but I assume lighting??

DLI can be misleading under lights. What people don't often realize is light intensity falls as the square of the distance. 4000 lumens at 6" from a light panel falls to 1000 lumens at 12". The sun is 93 million miles away. The intensity drop from 93 million miles to 93 million miles + 6" is negligible ;)

In practice, this means that under lights you can burn the upper canopy while freezing the lower one :( For example:

20221124_065848.jpg 20221124_065855.jpg

The top of this tiger bark ficus was receiving in the neighborhood of 30K lux for 16 hours while the bottom was receiving ~10K lux. The tree is just shy of 24" tall. What does DLI mean if the top of the tree gets 4x more than the bottom? There is more foliage at the wider base...but it gets less intensity.

Some of my trees I illuminate from the side to get a wider area of foliage under a more uniform intensity. But even then, the back is shaded and I need to rotate to avoid phototropic effects.

I haven't yet seriously measured my new setup...I had to buy new hard to find batteries for my PPFD meter! But here is some data from my previous setup in a former home:

PPFD from where one of my willow leafs summered:

outside_ppdf.jpg

PPFD at mid canopy from where that same tree wintered:

window_no_lights_ppdf.jpg lights_in_window_ppfd.jpg

The first plot is without the lights on...just window light. The second is with the lights on...this was in a living space so I had lower output supplemental lighting in an already bright window. The "shoulders" on the second plot are the artificial light. The sun, even through a window, dwarfed the artificial light output!

That ficus was about 18" tall at the time. These measurements were about mid canopy. 12 PPFD was enough to keep the tree full and healthy looking. No growth...but too cold in that window for much growth anyway.

I can't find the plots right now, but I did similar for my BRTs...which are a little taller than 24" I kept the upper canopy at about 15 PPFD and it did well...even grew some once it got warm enough.

But, honestly, all that is just fun numbers to entertain me. In practice, all that is really needed is some basic familiarity and some rules of thumb. Most trees...especially tropicals...have a "tell" when they are receiving an acceptable amount of light. The ficus picture above is telling me that the upper canopy is receiving about the right amount of light because that lightish green color is what I would expect from a health ficus kept outdoors. The color of the lower canopy is too dark...it's not getting an optimal amount of light down there.

BRT's tell is that they tend to grow larger leaflets in dimmer light. Sorry, I don't have pictures, but mine grow leaflets that are about 2x larger when inside for the winter than when outside for the summer. They are also darker in shade. Mine drops all its leaves when moved inside to out or outside to in so there are rarely both styles of leaf on it at the same time.

As a rule of thumb, you can often get away with this: hold your hand at canopy height and observe the shadow below. For a "full sun" plant, if the light source casts a sharp shadow...you can count the fingers...it's "bright enough" and a 10-12 hour day should be plenty. If the shadow is diffuse...a noticably darker patch but can't count fingers...then increase the duration to closer to 14-16 hours. If there is no noticable dimming, the light is too dim and no amount of increased duration will "catch up" to bright light.

NOTE: if your light source is a panel or long tube or some other extended form you might not get a shadow even under very bright light.
 

groffralph

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You could use a map as a benchmark (as in if you were to live in a region where you could grow a tropical outdoors, what DLI could you expect there?). https://news.clemson.edu/new-national-light-maps-help-greenhouse-growers-manage-plant-growth/

But it sounds very difficult to match tropical sun in output especially if you're only doing 12 hours. For overwintering my tropicals/cacti/succulents, I think 25-30 is OK. Looking at the map I linked, the winter levels for Florida are around 25-30 anyway.
That sounds like good advice, thanks a bunch! I have them in various positions. I should be receiving my PAR meter soon, I will keep you all posted.
 

groffralph

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You don't mention if under lights or natural lighting...but I assume lighting??

DLI can be misleading under lights. What people don't often realize is light intensity falls as the square of the distance. 4000 lumens at 6" from a light panel falls to 1000 lumens at 12". The sun is 93 million miles away. The intensity drop from 93 million miles to 93 million miles + 6" is negligible ;)

In practice, this means that under lights you can burn the upper canopy while freezing the lower one :( For example:

View attachment 463927 View attachment 463928

The top of this tiger bark ficus was receiving in the neighborhood of 30K lux for 16 hours while the bottom was receiving ~10K lux. The tree is just shy of 24" tall. What does DLI mean if the top of the tree gets 4x more than the bottom? There is more foliage at the wider base...but it gets less intensity.

Some of my trees I illuminate from the side to get a wider area of foliage under a more uniform intensity. But even then, the back is shaded and I need to rotate to avoid phototropic effects.

I haven't yet seriously measured my new setup...I had to buy new hard to find batteries for my PPFD meter! But here is some data from my previous setup in a former home:

PPFD from where one of my willow leafs summered:

View attachment 463930

PPFD at mid canopy from where that same tree wintered:

View attachment 463931 View attachment 463929

The first plot is without the lights on...just window light. The second is with the lights on...this was in a living space so I had lower output supplemental lighting in an already bright window. The "shoulders" on the second plot are the artificial light. The sun, even through a window, dwarfed the artificial light output!

That ficus was about 18" tall at the time. These measurements were about mid canopy. 12 PPFD was enough to keep the tree full and healthy looking. No growth...but too cold in that window for much growth anyway.

I can't find the plots right now, but I did similar for my BRTs...which are a little taller than 24" I kept the upper canopy at about 15 PPFD and it did well...even grew some once it got warm enough.

But, honestly, all that is just fun numbers to entertain me. In practice, all that is really needed is some basic familiarity and some rules of thumb. Most trees...especially tropicals...have a "tell" when they are receiving an acceptable amount of light. The ficus picture above is telling me that the upper canopy is receiving about the right amount of light because that lightish green color is what I would expect from a health ficus kept outdoors. The color of the lower canopy is too dark...it's not getting an optimal amount of light down there.

BRT's tell is that they tend to grow larger leaflets in dimmer light. Sorry, I don't have pictures, but mine grow leaflets that are about 2x larger when inside for the winter than when outside for the summer. They are also darker in shade. Mine drops all its leaves when moved inside to out or outside to in so there are rarely both styles of leaf on it at the same time.

As a rule of thumb, you can often get away with this: hold your hand at canopy height and observe the shadow below. For a "full sun" plant, if the light source casts a sharp shadow...you can count the fingers...it's "bright enough" and a 10-12 hour day should be plenty. If the shadow is diffuse...a noticably darker patch but can't count fingers...then increase the duration to closer to 14-16 hours. If there is no noticable dimming, the light is too dim and no amount of increased duration will "catch up" to bright light.

NOTE: if your light source is a panel or long tube or some other extended form you might not get a shadow even under very bright light.
That is awesome food for thought, thank you! I'm getting my PAR Meter and Tent soon. I will post my findings as I have plants in various positions ie. Windows supplemented w/ lights, shelving w/out much natural light, basement w/little natural light, and soon a grow tent!
 

groffralph

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Thank you all for valuable info. I'm just getting into topicals and I have them in various positions ie. windows supplemented w/ lights, shelving w/out much natural light, basement w/little natural light, and soon a grow tent!

I will post findings as I know more.
 

groffralph

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Wow! That is a lot of stuff I would need to make room for in my head.
I think I'll just do what I have been doing for decades. It seems to work.
If it works keep on rolling!
 

LittleDingus

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Wow! That is a lot of stuff I would need to make room for in my head.
I think I'll just do what I have been doing for decades. It seems to work.

This is very much me...do what has been working for me for decades :) Without realizing it, I tend to have indicator plants that I am very familiar with in all my grow areas. In that area, I know that orchid turns purple under too much light, in that area, the croton turns too yellow under too much and too green under too little, etc...

A lot of hobbiests...especially newer ones...aren't aware of the indicators. Some learn them...some don't. When learning anything new, it helps to have an anchor to reference from. The most universal anchor is the numbers. Even the newest beginner can look at maps like this:


to see what full sun in their area is. There are apps you can get for many phones that will give you an instant lux reading (the measurement is camera sensor dependent and not all apps are calibrated for all phone sensors). From there it is simple math to compute what your setup sees in a day.

Granted, someone may need to explain where to find these resources to someone new to them ;)

Because of my scientific background, I like to play with numbers sometimes so I bought myself a decent lux meter and a more fancy PPFD integration meter. I intended to do a deep dive into comparing the somewhat expensive PPFD to what your cell phone camera can measure but haven't gotten past the "phone seams good enough" phase yet.

What I have learned from the numbers so far is that trees are somewhat forgiving of a wider range of light intensity than one might think. Most deciduous trees can adjust leaf size and number to optimize energy gain, for example.

Sorry: too many words! I'll go back to lurking again...
 

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I have shop lights with daylight bulbs over my trees. I use one 3 bulb fixture for one table and 2 of those for another table
15 hours per day.

Trees grow most of the winter so if it works, dont fix it is my thoughts

20210104_171655.jpg
 

groffralph

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I have shop lights with daylight bulbs over my trees. I use one 3 bulb fixture for one table and 2 of those for another table
15 hours per day.

Trees grow most of the winter so if it works, dont fix it is my thoughts

View attachment 463961
Agree Totally! Love the BT's, they look amazing.
 

groffralph

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I have shop lights with daylight bulbs over my trees. I use one 3 bulb fixture for one table and 2 of those for another table
15 hours per day.
I have shop lights with daylight bulbs over my trees. I use one 3 bulb fixture for one table and 2 of those for another table
15 hours per day.

Trees grow most of the winter so if it works, dont fix it is my thoughts

View attachment 463961
What is you fertilizing regime for the Brazilian's. What type of fertilizers do you use?

Trees grow most of the winter so if it works, dont fix it is my thoughts

View attachment 463961
 

groffralph

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I have shop lights with daylight bulbs over my trees. I use one 3 bulb fixture for one table and 2 of those for another table
15 hours per day.
I have shop lights with daylight bulbs over my trees. I use one 3 bulb fixture for one table and 2 of those for another table
15 hours per day.

Trees grow most of the winter so if it works, dont fix it is my thoughts

View attachment 463961
What is you fertilizing regime for the Brazilian's. What type of fertilizers do you use

Trees grow most of the winter so if it works, dont fix it is my thoughts

View attachment 463961
 

groffralph

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I have shop lights with daylight bulbs over my trees. I use one 3 bulb fixture for one table and 2 of those for another table
15 hours per day.

Trees grow most of the winter so if it works, dont fix it is my thoughts

View attachment 463961
What is your Fertilizing regime for the BT's(Fert types, timing, etc.)? They look amazing, any recommendations would be greatly appreciated.
 
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