I’m Bruce Bugbee, president of Apogee Instruments
and also professor of Crop Physiology at Utah State University. In this video today, we’re
going to talk about the basics of lighting as it applies to cannabis. This is profoundly
misunderstood. The database is filled with a lot of myths that we have studied over the
past year. And so we’re calling this Cannabis 101. This first part of the series is just
focused on lighting, which is one of the key parameters. Apogee has spent decades refining
instruments to quantify light, the types of light, the intensities of light. Those, in
my experience, those instruments are underutilized to help refine the cultivation of cannabis.
And part of it is just because people don’t know how to interpret the data and how to
make the measurements. As a company, Apogee instruments motto is “we help people make
measurements.” And part of that is our ongoing education to help people interpret the data
that they get, make sure the measurements are high quality, and that’s what this video
is about. With a focus on cannabis. We’re not focused on all the other crops like lettuce
that’s grown under electric lights. Just cannabis. Utah State University is one of the few agricultural
universities that now has a license to study hemp at the University. And when I say cannabis,
I mean both hemp and marijuana. Our license isn’t for marijuana. It’s only for hemp. But
the studies apply to both types of cannabis. So I’m going to talk about cannabis in this
video. So, it’s pretty hard to underemphasize the importance of light when you’re growing
a crop. And this next slide, which I’ve used many times in many talks, really focuses on
that. Here’s the nine cardinal parameters. If you were to take a university class, you
would be reviewing each of these parameters. Four of the parameters are in the foliar environment:
temperature, humidity, air velocity or wind, and carbon dioxide. Four in the root zone
environment: we have temperature down there, amount of water, nutrients, and oxygen. We
teach whole classes on each one of these parameters, and we may do a series on cannabis on each
one of these parameters. But today we’re going to focus on the one that is absolutely critical,
and that’s light. And we put this right at the top… let’s see if this… see if we
can get this back… and then let’s go to pen tool… there. There we go. Light… and
let’s see if we can get that yellow to emphasize the light. Light is coming in from all directions
on this plant and it drives the optimum levels of everything else. If you turn the light
up, you have to give the plants more water because it drives the flux of water through
the plant… I should have drawn this in yellow or in blue for water flux in the plants. You
turn the light up, you need more nutrients, you need more oxygen in the root zone. It
drives everything. So often we get questions from people saying “My light must be too
high. My plants are turning yellow or purple or some color.” What it really is is an
imbalance between the amount of light and the optimum levels of all these things. It’s
like a racecar. Cannabis is a race car that can go incredibly fast. If everything is optimum,
you can give cannabis exceptionally high levels of light. And I’m going to go into how we
measure that and quantify it. If all of these other parameters are also optimum. If you
give it more light and you don’t have the right nutrient balance, or the right water,
or you don’t have elevated CO₂, you’re going to have problems with the plant. But it’s
not fundamentally caused by the light. It’s caused by inadequate levels of the other parameters.
Be like a racecar. I’m saying you got a giant engine, you’re out at the Utah Bonneville
Salt Flats, you’re going 700 miles an hour, and the tires blow on the car. And you say
ah dang it the engine was too big. No the engine wasn’t too big! You didn’t have the
right tires for that big of an engine. That’s the analogy of how important it is to get
the lighting right. So let’s start with how we even measure light. So many people say
how much light do I need? And they’ll say oh keep your plants about 30 centimeters,
about a foot, away from the lights. Let me show you how bad that is as a measurement
of light. And in order to do this, we have set up here in the Apogee studio two lights
of different wattages. And I’m going to do a demonstration now to show you how important
that is. So I’ve got to step over here and plug the light in. Wheel this in… now here’s
two lights. Let’s get them right in the screen. Two different wattages of lights. They’re
both LEDs. I could turn them toward the screen, it’d be incredibly good. Now we’ve set this
up so we can measure… if I can do this… right there. We can measure the intensity
of the light from these. Here’s the number right here. We’ll get into what this means
in just a second. But it’s 27 µmols of photons right now. That’s the light from the studio.
If I put this over here… 7 µmols. Now the 7 is plenty of light for humans to work in.
A well-lit office has 7 µmols. That is way too low to grow cannabis. You can tell these
are a little brighter. What if we said it’s 7 µmols here, how bright is it over here?
Oh it might be 50 µmols over here. Let’s take a look. We’re going to go under this
light. Now let’s see if we can do this. Can you see the screen? I think you can. I’m going
to hold this right here about a foot away. You see the number we’re getting? 300 µmols.
A well-lit office is 7 to 10 µmols? And this is 300 µmols? And it looks a little brighter,
but it doesn’t look 20 or 30 times as bright. It’s much much brighter. That’s a foot away.
What if that was our measure for cannabis, and we say here’s another light let’s go a
foot away? Now we put it under this light. Look at this. I got to get it centered. 3000
µmols. Depends on exactly how far away, but we’re approaching 3000 µmols. If I go a hair
closer there it is, 3000 µmols under this light. And we go under this light. Same distance.
We’re down around 300 µmols. That is almost an order of magnitude more photons under one
light than the other, and the only difference is the input wattage. This is a low input
wattage. This is a high input wattage. It’s not color of light, it’s input wattage.
So I hope you can see that just saying put your plants some distance away from the lights
is a very inadequate way to precisely grow cannabis. You’ve got to have a meter. Our
eyes are one of the worst meters for plants. Our pupils contract to reduce the amount of
light getting to our retina in bright light. So we’re a terrible light meter in terms of
intuitive estimating of light. We really need an instrument to measure it. So this is a
demo of the fact that you can’t do that. Now remember that number. Let’s take 300 µmols,
and how much cannabis could we grow with that? Now I’m going to stop here and take these
out of the way so we can interpret the data… Now we’re back with a white screen that we
can take a look at what we just measured. So, first of all, let’s draw what we call
a light response curve for plants in general, and then we’ll draw a light response curve
for cannabis. So as students in my classes know over the years I draw a lot of XY plots
to take an input variable here and look at response. So what we’re going to put over
here is Pn. This stands for net photosynthesis. And over here we’re going to put PPFD. Photosynthetic
Photon Flux Density. That’s what we just measured with that Apogee meter. This graph starts
at zero here, and zero here. If this was Introduction to Plant Science and we asked this question,
everyone would say well of course light, or photon flux, drives photosynthesis. So that
curve is going to look like that. And if this was Plant Science 101, we would count that
as a correct answer. But if it’s a more advanced class, we know that the higher the light this
doesn’t keep going up forever. Plants can’t keep using all those photons. So a more correct
answer looks like this. And we can even erase this top incorrect answer and go back to this.
There’s a more correct answer because it levels off at high light. Now notice I didn’t put
any tick marks on here yet because we just measured 300 µmols and almost 3000 µmols
out of that other light. But there’s one more thing that makes this curve even more accurate,
and I’ll put that in blue. If you take a plant and put it in the dark, it gradually respires
and dies. You can’t keep it in the dark for weeks or months. So this line doesn’t go through
zero right there. In the dark, we get a negative number. The plant is shrinking. It’s dying.
And we turn on the lights, and it goes like this. So there’s some point right here where
there’s just enough light to keep the plant alive. This, by the way, is called the light
compensation point when there’s enough light to get it to zero. Now let’s put some tick
marks on this axis. Photosynthesis… oh let’s make this go to 60 up here. Now the units
for this are µmols per m² of leaf per second of time. This is how fast it’s fixing carbon
and dry weight. Now let’s put some tick marks on this. If we go up to here, what’s full
sunlight? If we went outside in the summer at noon what would we get for high light?
We would get 2000. That’s an important reference point, 2000. These units are µmols of photons
per m² per second. And this over here could be just yield of the plants, but these are
the units that we’re measuring to get the light. Now if that’s 2000, 1000 is right here,
and 500 is right here. On… the way I drew this graph… Wow. We have to have 400 µmols
just to get above zero. Now this only happens in a dense crop. But let me see if I can erase
this… erase these lines… and I’m going to draw two lines on here… let’s go back
to green… We’re going to fill this back in. Here’s our green. There’s 500. Now let’s
go to blue. If we did these measurements for lettuce. Lettuce is a widely grown crop. Very
widely studied. It is also a low light plant. Lettuce grows fine in much lower light than
cannabis. So if we draw a curve for lettuce, first of all it starts here. It goes up, and
at about 500 µmols lettuce is done. And it might even go down out here with really high
light. This is lettuce. There. Now what if we put cannabis on here? Cannabis is life
in the fast lane. It takes a lot of light. You can grow cannabis much faster. We’re going
to put cannabis in red. First of all, it doesn’t really have a low gear. It has a high respiration
rate. Cannabis looks something like this. Look at this curve! Look at that curve! Wow!
This is cannabis. It keeps going up until 2000 µmols. So cannabis is a very high light
crop. You can give it a lot of light, but you’ve got to have all the other inputs optimized.
For sure you need elevated CO₂ for cannabis. And ample water. It’s usually automated watering.
It’s a balanced nutrient solution. That’s a topic of a whole other talk. But our data
don’t indicate cannabis needs unusual nutrients, but it needs a balanced nutrients. And not
too much. Usually there’s toxicities from too much nutrients. And if you have this high
light, and the water is going through the plant that fast, you have to be careful not
to have too much nutrients. But the point is, look at cannabis. Corn is like this, too.
Corn is a very high light field crop. So now we get a meter to measure this. And if the
leaves are green, we’re using the photons efficiently, and we have high photosynthetic
rates. Let’s take a look on this now. A closer look at this unit down here. This is generally
a widely used unit, but it’s not universal. And let’s take a look at this. And I can do
that on the next screen. Now let’s go back to green. Multiple acronyms are used to measure
light. And the most common one is PAR, and the P always stands for Photosynthetically
Active Radiation. Let’s go to a slightly smaller… line size… That’s a pretty fat line. All
right. Now we’ve got a PAR. This is a generic term for all photosynthetically active radiation.
But it could mean watts per meter squared, and that’s confusing. So a more rigorous term
is PPFD. That stands for Photosynthetic Photon Flux Density. And this always means that number
from the previous one, moles of photons. And you think of photons as like tiny little marbles
falling out of the sky to fill a box. They can be colored marbles, but they’re all marbles.
We’re measuring this flux of photons coming into the plant. Per meter squared per unit
area of a surface area per unit time, and we always use per second. That’s the unit
for PPFD. Now this is a big number. A mole. And so it’s really a µmol. Ten to the minus
six moles per second. And this number ranges, we just showed that in the other slide, zero
up to 2000 µmols. It’s a huge range. Remember those lights we measured? One was 300 µmols.
One was over 3000 µmols because it was a high wattage light, and we’re real close to
it. These are the keys. Now we’ll come back to this later but PPFD is the number that
we’re after here for light. Now let’s go to another screen. We’re going to take our
same screen here. And we had PPFD. Zero. Let’s go all the way to 2000. This is very bright
light. We rarely get this high of light under electric lights, but we could. And over here
we’re just going to put yield. Not photosynthesis anymore because photosynthesis leads to yield.
How much light is necessary? What’s really key about this is not the instantaneous light.
We’re going to put our graph on here again. Something like this. The exact shape varies
with different cultivars, but it doesn’t vary very much. It turns out it’s not exactly the
PPFD, it is the DLI. Daily Light Integral. So as this implies an integral, it means we
add up all of the photons. This is per second, and every second we accumulate them. What
if this was rainfall? PPFD would tell us the rate. How fast is it raining per second? But
usually what we want to know is how much did it rain yesterday? The total amount of rain.
And that’s the daily light integral called DLI. Let me show you how to convert. Once
you see this you’ll know it forever. Let’s put 1000 in here. We’re going to convert from
PPFD to DLI. 1000 µmols per m² per second. Now we want to know per day. Well there’s
3600 seconds per hour. So this is 3.6. Now notice this is 1000, and that’s 3000, and
when you multiply these together the thousands cancel. And this is 3.6 moles. Now no micro
anymore because we just multiplied two big numbers together. 3.6 moles per m². Now this
is per hour. We’re still not there. That’s per hour. For cannabis, when it’s in the flowering
stage, we would typically give it 12 hours per day. Multiply these two together: 3.6
and 12. I know this because I’ve done it so many times. That comes out to be 43.2 moles
per m² per day. And that number right there this is so important we’ll put it in red…
is the DLI. If you had 1000 µmols per second continuously for 12 hours, you get 43 a day.
This is high light, but cannabis responds to this. In our studies, we can push them
even higher than this. We’ve never gone to 2000 µmols, but we’ve gone close to it. We’ve
gone to 1800 µmols up to where we’ve gotten this number close to 60. Outside in the summer
under full sunlight on sunny days DLI can get to 60 moles per m² per day. That’s an
incredible DLI. Cannabis grows outside in full sunlight, and it loves it. It responds
to it. So you can run the DLI up extremely high. Now how low can you go? Well here would
be 500 µmols. And you see the point here. There’s some diminishing returns. The line
still goes up, but it’s curving over. So 2000 µmols doesn’t give us twice the yield of
1000 µmols, but it’s still higher. So we keep raising this… here would be 500 µmols
right here. But the point is, you’ve got to know this input to have reproducible studies,
and to get it you need to measure it. Let’s take a second to review some of the instruments
that Apogee uses. All of them are a little sensor. Here the quantum sensor is blue. That’s
the one we used a minute ago to measure these. This one plugs right in to a laptop. Here’s
a USB cable, and you can plug right in. You’ve got to remember to take the cap off of these.
The optics here are really rugged, but we still ship them with the cap to keep them
perfect. Plug this right into a laptop just like I did, and you’ll see the numbers on
the screen. If you want something more portable, here is a handheld meter with a separate sensor.
These also come with the sensor right in it. That’s another option. And one of the options
that’s big and catching on fast is Bluetooth. This is a Bluetooth module. It’s like a
data logger. It measures and stores the data, and then you just transmit this data right
to your cell phone. So this is a powerful option and there’s plenty of graphics associated
with this for measuring the light. All of them go to this sensor. If you jump up another
level, this gold cube is a spectroradiometer, which gives you all the ratios of colors.
But these other instruments are down in a few hundred dollars. This instrument is over
two thousand dollars. It’s much more sophisticated, but this is what researchers use to get everything
exactly right in all of these. So we get questions all the time on issues relating to light.
And I just addressed one of them: daily light integral (DLI). We can push daily light integral
easily to 30, to 40, to 50. And the yield keeps going up if everything’s optimal. Let’s…
in terms of how much light it tolerates, this is true even for young seedlings. We once
took… one of our research projects right now is to push the rooting of cuttings of
cannabis with very high light. This just sounds amazing. But for years and years we keep plants
in really low light with cuttings because they didn’t have any roots. We’re finding
if we can keep them watered we can even push a cutting with very high light levels. And
certainly a young plant. You can push them hard with high light. Again as long as the
other inputs are not limiting growth. What about darkness? Let’s go to another screen.
Another topic. We’ll put this one in blue. Now we’re going to do hours per day. It’s
a different graph. Hours. Here’s noon. Here’s midnight. And here’s midnight. And of course
here’s PPFD. We have no evidence that suddenly turning on the light shocks the plants. They
can get out of bed and go right to work. They don’t need to ramp up slowly. But let’s say
we turn on the lights at 6:00 AM. We run them high until 10:00 PM. If we ran… this would
be 16 hours of light. Now if we’re in flowering phase… let’s go back to red… if we’re
in flowering phase we might run them from 8 AM to 8 PM like this. And this is a 12-hour
photo period. So there’s really just two photo periods for cannabis. A 16, and even an 18
hour, photo period for veg. And in fact some of our data indicates this could even be 24
hours per veg. Just get the plants growing with a high DLI. And then when we want them
to flower, we switch to 12. Now here’s the question. So this is all fine. What about
right here? This number right here is darkness. How dark does it have to be for cannabis at
night? This is something we’re actively studying right now in my laboratory at the University.
There are some literature reports that indicate that cannabis is exquisitely sensitive to
trace amounts of light pollution. Just a little bit of light will cause problems with cannabis.
We have a wealth of literature on poinsettias. They’re one of our most sensitive crops to
light pollution. Without excellent darkness, those top leaves of cannabis don’t turn red.
They’re called Brax. They don’t turn red. Is cannabis more sensitive than poinsettias?
We don’t know yet, but we know it needs to be very dark. We call this reagent grade darkness,
and it’s like somebody sleeping. Some people are bothered by a tiny light sleep and other
people it doesn’t matter. But we think cannabis is quite sensitive to this. For this reason,
Apogee has made an extended range quantum sensor that’s calibrated to rigorously measure
light pollution. Now remember we were doing µmols per m² per second and were getting
numbers in the hundreds? This particular sensor can measure 0.01 µmols per meter m² per
second. It’s a unique meter that can detect trace amounts of light. And it helps you determine
whether it’s absolutely dark. It’s an extended range sensor. It even picks up the photons
from security cameras, which there’s possibilities for those to affect cannabis. That’s a topic
for another video. So extended range quantum sensor for light pollution studies. This is
getting down around full moonlight, and we know that full moonlight doesn’t affect cannabis
or any other plants. But it might not take much more of that to be a big deal. Let’s
talk about cultivars, differences. Many people say geez this happened in one, and something
else happened in another. We have an emerging number of different cultivars for cannabis.
As you probably know if you’re watching this video, I won’t write them up here, they’re
all cannabis sativa. And underneath that we have indica and sativa. So it’s cannabis sativa
sativa. Our studies at the University indicate there’s definitely differences in those. Leaf
width. Leaf size. But in terms of response to all these parameters I’m talking about,
there’s not a significant difference between the types. You can push both types of cannabis
with high light. They both love high light. They both evolved out in the field. The differences
can be in yield. They can be in photo period sensitivity. Some cultivars of cannabis we
think can take 13 hours of light over here. Some might be able to take 14. But in terms
of pushing them with high light, they’re all similar. Let’s think about some of the other
cultivars. One of them… some of the other questions we get… one of them is what about
light quality and the synthesis of what we call cannabinoid compounds. That’s THC, CBD,
CBN, CBG, all the different cannabinoid combos. Then in another class of compounds there’s
terpenes. What about light quality? And it could be a whole other talk, and I have given
other talks on this. They’re in other videos on the Apogee website. So if you’re interested
in this, look for other videos on this. Here’s the take home message. We don’t have evidence
that changing the colors of light makes a significant difference on cannabinoid synthesis.
Let me say that again this is an amazing statement. Light quality does not have a huge effect
on the ratios of cannabinoids. This is in spite of many people claiming it does. Our
data in general don’t support that there’s big effects. I didn’t say there was none.
We just don’t see big effects. We’re still actively studying that, and stay tuned because
we’re looking at all kinds of different ratios. Now let me conclude on one part of light that
is enormously important. And we’re going to go to a new screen. Last slide… I don’t
like to draw those… I’m going to draw the axes in blue. This is 400 to 700 nm. And
this is the wavelength of light. If you’re going to get a degree, an honorary degree,
in cannabis science you got to memorize these two numbers… We use lambda to express this.
And the unit here is nanometers. So this is colors of light. This is what you would use
this spectroradiometer to measure. So I think most people know, but let’s review this. Right
here if we do 500 and 600 nm. This area right here, 400 to 500 nm, is blue. It looks blue
to the human eye, and we call that range blue. Now we go to 500 to 600 nm, and that range
is green. And now we go to 600 to 700 nm, and that range is red. For many of you this
is review, but it’s important to have the basics. Alright, photosynthetic radiation
stops right here. Our historic and classic definition of this is 400 to 700 nm. Period.
If there’s a photon at 701 nm, we don’t count it. If it’s at 399 nm, we don’t count it.
Is that right? Really? The big chop? No, they don’t chop off like that. We’ve known that
for years. This is just a useful approximation of photosynthetic radiation. But, now that
we have LEDs that we can fine-tune all these wavelengths, we are reexamining what we have
used for half a century. And there’s two specific wavelengths that are huge. I think I’m still
on red. Right here… no let’s go to red… right here this is far-red… if I can get
that up here… FR. Rar-red. Now we’re going to look at far-red. And that is out here to
750 nm. Right here. Our eyes have trouble seeing this. It’s just like a dull glow of
a red burner on a stove or electric burner. You couldn’t read a book by this. But it has
powerful effects on plants, and it adds 750 nm. Our data indicate that these photons cause
photosynthesis. They certainly cause changes in plant shape. We can make plants branch
more. We usually make them taller with more far-red. But these photons are critical. Because
of that… well before I get to that… let’s talk about the other end down here. Blue.
These photons, especially 350-300 nm. This of course is all ultraviolet. Our eyes don’t
see this. Historically electric lights we try to get rid of this. We try to get rid
of this. They’re not useful for human lighting, but they have powerful effects on plants.
Especially this region at 350 nm right here of UV. Our data indicate these photons cause
photosynthesis as well. So I think we’re going to see an emerging change in the definition
of photosynthetic radiation maybe from 350 to 750 nm. We’ll see. Multiple laboratories
are studying this. Because of this, Apogee has come out with what we call an extended
range quantum sensor. And that is a sensor that measures everything from 350 nm way out
here. It picks up… here’s security cameras, they have a big peak out here that’s centered
around 830 nm. That extended range picks up all these photons. And for some kinds of lights
these photons are critical. You want to know what they are. Even though the classic quantum
sensor doesn’t include them, the Apogee extended range quantum sensor does include them. So
UV photons have the potential to reduce disease in plants. They have the potential to trigger
cannabinoid synthesis in plants. So we’re putting a lot of energy into studying the
potential use of UV photons in plants. Again stay tuned. And one more thing, we get a lot
of questions about optimum ratios of colors for both growth and photosynthesis and for
cannabinoids. And let me fall back on the one principle here that has guided us, and
that’s the percent blue photons. And let’s do this in a different screen… here’s my
marker… for years, before we had LEDs, people said you want to do metal halide
for veg before they became reproductive. And you would typically be giving oh maybe even
an 18 hour photo period during that time. During veg. Then the prevailing wisdom was
the switch to high pressure sodium during the reproductive phase. And that’s flowering.
Now many people said oh god that’s all a myth… Not exactly. Metal halide has 30% blue photons…
this is having trouble… 30% blue. The higher the blue photons the more compact the plant.
So metal halide was very effective at making nice compact plants. High pressure sodium,
on the other hand, only has about 4% blue photons. Sunlight has about 30% blue. They
switch to high pressure sodium because it’s a much more efficient light, and you can get
bright intensity. But it had low blue. But the blue didn’t matter so much during flowering
because the flowers kept the plants short. So there was a reason to go with a high blue
light during veg and then a very efficient light during flowering. And we’ve seen that
in cannabis. It’s a ratio of blue photons for plant height and then the efficiency of
the light after that. So what we like to see are very efficient lights. The ratios of colors
are less critical. We do like to see lights with enough green photons so you can diagnose
plant disorders. Those green photons usually come from white LEDs. It’s important to look
for microscopic insects. Subtle disorders. You’ve got to be able to see the plants
to do that. But after that, it’s just the efficiency of the light. If you search for
design light consortium on the internet, the acronym is DLC. That is an independent company
that has now been listing many lights from many manufacturers and their test results
from independent test laboratories for the efficiency of the light. The unit for light
efficiency… and not a lot of room… is… put this over here… is µmols of photons
out per Joule of electricity in. The really efficient lights, LEDs, are now getting up
to 2.5 µmols per Joule and even higher than that. They’re incredibly efficient. Ten years
ago, we were half of that efficiency for lights. But it’s critical to get an efficient light
and a broad spectrum light so you got enough colors to see the plants. Thanks for listening.