Who needs a PAR Meter

[BluNGreen]

So, who really needs an expensive light meter just to check how much useable light your plants are really getting. I can tell by just how the plants are responding to the up and down adjustments. Also making sure all of the plants are under the lights.

Photosynthetically Active Radiation (PAR) is a measurement of useable light for indoor growers to understand as it refers to the portion of the electromagnetic spectrum that is essential for photosynthesis in plants. Each grow stage has a recommended PAR value allowing your plants to flourish. It has always been a guessing game with the Light to canopy distance and with multiple grow lights it is even more difficult.

Well after getting a PAR meter I was amazed on how easy it was to set my lights up for distance apart and height. And my thinking that the plants under the light are getting more light than the ones between the light. For instance, I run four Mars Hydro SC series LEDs. The two in the front have six plants between them in two rows of three. The lights are about two feet apart. the outside plants are basically under the lights, and one is between the lights. So old school growers (Which includes me) which plant is getting a higher PAR value/more light? Well, it is not the ones under the lights, by far it is the one between the lights. Using a meter, you can also determine where your lights drop off on the sides and then widen them out to the edges of your grow.

I tried the cell phone app (The free version) and it did not work for me. The meter i purchased was only $200 and worth the investment. I was getting Mac1 clones from a friend and for two grows with ten plants I averaged about 15 to 18 oz dry weight. The third grow same clones and quantity i had purchased the Par Meter. I had to widen my lights outward and used an extra light for "Side lighting" based on the low PAR values and my total yield was 56 ounces dry. the plants were just over 2 feet in height. I attached a pic of that grow and I believe they were in week 7 at the time of the photo, Been using the meter ever since.

Happy Growing

 

[SSgrower]

I have tent micro climates but you have a grow room huh. Have a look GML or Grand Master Level led lighting for horticulture, many settings and side lighting available, tell Spartangrown SSgrower sent you for a discount. Cheers SS

 

[Fenderbender]

Have you measured between the lights and are you getting a higher value than under the light? could be from two lights combining as if well the intersection where the output from two lights cross should be higher.

Alternatively if the spot isn't stronger than under the light...If I supply a plant with all the par it needs it's not going to be incentivised to grow taller much as it doesn't need to it's got everything it needs, that's how you can keep plants short and stocky... for the plants in between the lights they might have less overhead making them search a bit and getting bigger.. lots of light coming in at an angle also makes them grow taller as you're giving all the nodes a boost.

 

[Wastei]

So, who really needs an expensive light meter just to check how much useable light your plants are really getting. I can tell by just how the plants are responding to the up and down adjustments. Also making sure all of the plants are under the lights.

Photosynthetically Active Radiation (PAR) is a measurement of useable light for indoor growers to understand as it refers to the portion of the electromagnetic spectrum that is essential for photosynthesis in plants. Each grow stage has a recommended PAR value allowing your plants to flourish. It has always been a guessing game with the Light to canopy distance and with multiple grow lights it is even more difficult.

Well after getting a PAR meter I was amazed on how easy it was to set my lights up for distance apart and height. And my thinking that the plants under the light are getting more light than the ones between the light. For instance, I run four Mars Hydro SC series LEDs. The two in the front have six plants between them in two rows of three. The lights are about two feet apart. the outside plants are basically under the lights, and one is between the lights. So old school growers (Which includes me) which plant is getting a higher PAR value/more light? Well, it is not the ones under the lights, by far it is the one between the lights. Using a meter, you can also determine where your lights drop off on the sides and then widen them out to the edges of your grow.

I tried the cell phone app (The free version) and it did not work for me. The meter i purchased was only $200 and worth the investment. I was getting Mac1 clones from a friend and for two grows with ten plants I averaged about 15 to 18 oz dry weight. The third grow same clones and quantity i had purchased the Par Meter. I had to widen my lights outward and used an extra light for "Side lighting" based on the low PAR values and my total yield was 56 ounces dry. the plants were just over 2 feet in height. I attached a pic of that grow and I believe they were in week 7 at the time of the photo, Been using the meter ever since.

Happy Growing

You are completely right. People focus more on numbers than plant response. PAR/ppfd meters should only be used to repeat and expand an environment on a larger scale. It's handy if you use different kinds of light on a larger scale but other than that it most often do more harm than good with newcomers pushing numbers instead of really learn by plant response.

Cheers!

 

[BluNGreen]

Have you measured between the lights and are you getting a higher value than under the light? could be from two lights combining as if well the intersection where the output from two lights cross should be higher.

Alternatively if the spot isn't stronger than under the light...If I supply a plant with all the par it needs it's not going to be incentivised to grow taller much as it doesn't need to it's got everything it needs, that's how you can keep plants short and stocky... for the plants in between the lights they might have less overhead making them search a bit and getting bigger.. lots of light coming in at an angle also makes them grow taller as you're giving all the nodes a boost.

Hey Fenderbender
Yes, the par is always higher in between the lights. During Veg I run Two 480-watt lights side by side and two 300-watt lights side by side with a 150-watt bar between the 300's. the way my system is set-up there is one plant in the middle and is not directly under any of the lights. Using a par meter the light intensity is higher in the middle. So, I have to balance the middle with the rest of the grow area using the dimmers.

And what you said about plants being complacent, not growing taller when getting everything it needs is something I have been experimenting with especially when growing from seeds. With clones most all of the plants will be somewhat similar in growth patterns with lighting being a major factor at keeping the canopy as flat as possible. My last grow and current grow are from seeds purchased from a large well know seed distributor. With seeds, same strain the plants are always different. There are always one or two that stay shorter than all the rest, like 10 inches tall when the rest are at 24 or so inches. I have tried all the light tricks to try and initiate vertical growth and they just grow slowly and wider. As a grower you know short is good but too short is not. I "Try" and wait until all of the plants are at least 20-24 inches before going to flower to maximize my height/light limits.

Any suggestions on getting a plant to gain vertically besides raising/dimming the light, or do you think it is just genetics?

Current grow is 22 days from seedlings breaking ground and growing faster/bigger than any previous crop (Gold Leaf and Rainbow Glue). And of course, I have one runt (Rainbow Glue) that is vertically challenged and one (Gold Leaf) that has been sickly from the beginning. The sick one (far right corner) has been responding to root inoculations. The runt plant right middle is healthy but short, kinda hard to see from the pic. I took this pic of the plants yesterday showing growth patterns with the plants under and between the lights. Keep in mind the plants are only 22 days old and were transplanted from solo cups into 5-gallon smart pots 14 days ago.

I have been using a battery operated fan for a few minutes a day to strengthen the stocks due to the weight of the leaves growing faster than the stem which is really not a bad thing.

 

[Delps8]

Alternatively if the spot isn't stronger than under the light...If I supply a plant with all the par it needs it's not going to be incentivised to grow taller much as it doesn't need to it's got everything it needs, that's how you can keep plants short and stocky...

You've got that flipped 'round.

Plants that don't receive a lot of light have to stretch. Plants that get a lot of light have the opposite characteristics - they're short and stocky, lots of small leaves, short internodal length, lots of inflorescence.

Check any Bugbee video or any of the research papers on grow lighting to details.

Or I'll write a tome about it!

 

[Delps8]

Hey Fenderbender
Yes, the par is always higher in between the lights. During Veg I run Two 480-watt lights side by side and two 300-watt lights side by side with a 150-watt bar between the 300's. the way my system is set-up there is one plant in the middle and is not directly under any of the lights. Using a par meter the light intensity is higher in the middle. So, I have to balance the middle with the rest of the grow area using the dimmers.

And what you said about plants being complacent, not growing taller when getting everything it needs is something I have been experimenting with especially when growing from seeds. With clones most all of the plants will be somewhat similar in growth patterns with lighting being a major factor at keeping the canopy as flat as possible. My last grow and current grow are from seeds purchased from a large well know seed distributor. With seeds, same strain the plants are always different. There are always one or two that stay shorter than all the rest, like 10 inches tall when the rest are at 24 or so inches. I have tried all the light tricks to try and initiate vertical growth and they just grow slowly and wider. As a grower you know short is good but too short is not. I "Try" and wait until all of the plants are at least 20-24 inches before going to flower to maximize my height/light limits.

Any suggestions on getting a plant to gain vertically besides raising/dimming the light, or do you think it is just genetics?

What I didn't post to @Fenderbender is below:

The plan in the photo is a 40 day old Glookie photoperiod. It's been at or very close to the light saturation point at all times. The plant is 20" across x 18" front to back x 8" tall and the foliage is extremely dense.

Three factors - the plant has been topped and LST'd; the plant has been grown using four lights; the plant has always been at or very near the light saturation point*, for that stage of growth.




As someone posted in one of my older grow journals, "Bushier than a 70's porn star!".


Light data from this AM

*The "LSP" is taken to mean 800-1000µmol but those values are for a mature plant. During earlier stages, light levels were very hight but not at the 1k level.
====================================

Why do you want tall plants? There are is one sure fire way to make them taller but, one, you can't harvest "tall", and, second, the only way to do it will reduce crop yield and quality. Easiest way to get a tall plant is to turn down the lights.

Check out some of the grow journals here or on other sites. The growers with tall plants and limited foliage that are yielding a few ounces don't have much of an electric bill. I expect the plant in the picture will end up yielding at least 18 ounces.

Cannabis will grow in as little as 64µmol (the "light compensation point"). If you turn your lights down, plants cannot generate food so they will slow sprouting new leaves and nodes, and will grow toward the light in their attempts to not die.

It's good that you ditched a software solution but a caution about the cheap PAR meters. One tidbit that I learned from the folks at Apogee is that any meter that uses a galium arsenide sensor cannot read light with a frequency of > 660nm so your readings might be a bit low for a white LED but they can't read anything above deep red and that will make a difference with new generations of lights.

RE. how to shape plants - there's no mystery. Blue is short and compact, lots of leaves, short internodal space. Red heavy light encourages cell growth. More light=more weed. More light = shorter more compact plants, higher crop quality and higher yield; less light = tall and stringy. Happy to cite but check out Bugbee or just Google "plant morphology".

 

[Fenderbender]

You've got that flipped 'round.

Plants that don't receive a lot of light have to stretch. Plants that get a lot of light have the opposite characteristics - they're short and stocky, lots of small leaves, short internodal length, lots of inflorescence.

Check any Bugbee video or any of the research papers on grow lighting to details.

Or I'll write a tome about it!

? isn't that what I'm saying? If I'm giving enough or too much she's not going to have the incentive to grow taller.
If you feed the sweetpot it will stay stocky and bushy and if you keep it out of reach they will follow.
If you'd simulate a daylight curve with the plants that would have them chasing as well, low power start, build up to a sunny afternoon and then dim down again till night time.. or even just cutting an hour or half hour.

 

[Wastei]

What I didn't post to @Fenderbender is below:

The plan in the photo is a 40 day old Glookie photoperiod. It's been at or very close to the light saturation point at all times. The plant is 20" across x 18" front to back x 8" tall and the foliage is extremely dense.

Three factors - the plant has been topped and LST'd; the plant has been grown using four lights; the plant has always been at or very near the light saturation point*, for that stage of growth.




As someone posted in one of my older grow journals, "Bushier than a 70's porn star!".


Light data from this AM

*The "LSP" is taken to mean 800-1000µmol but those values are for a mature plant. During earlier stages, light levels were very hight but not at the 1k level.
====================================

Why do you want tall plants? There are is one sure fire way to make them taller but, one, you can't harvest "tall", and, second, the only way to do it will reduce crop yield and quality. Easiest way to get a tall plant is to turn down the lights.

Check out some of the grow journals here or on other sites. The growers with tall plants and limited foliage that are yielding a few ounces don't have much of an electric bill. I expect the plant in the picture will end up yielding at least 18 ounces.

Cannabis will grow in as little as 64µmol (the "light compensation point"). If you turn your lights down, plants cannot generate food so they will slow sprouting new leaves and nodes, and will grow toward the light in their attempts to not die.

It's good that you ditched a software solution but a caution about the cheap PAR meters. One tidbit that I learned from the folks at Apogee is that any meter that uses a galium arsenide sensor cannot read light with a frequency of > 660nm so your readings might be a bit low for a white LED but they can't read anything above deep red and that will make a difference with new generations of lights.

RE. how to shape plants - there's no mystery. Blue is short and compact, lots of leaves, short internodal space. Red heavy light encourages cell growth. More light=more weed. More light = shorter more compact plants, higher crop quality and higher yield; less light = tall and stringy. Happy to cite but check out Bugbee or just Google "plant morphology".

More light is not better if the plant can't optimally use it. Dark period mostly decide internodal length. Having a small compact plant is not necessarily desirable and quality isn't better because of it, that's a false statement.

A smaller stouter plant has less coverage than a plant with more desirable internodal length. You want to fill space and have a fast turnover growing Cannabis for profit and pushing light to grow small stout plants that doesn't cover the space in the same veg time as a plant receiving the optimal is not advisable. There's a positive to negative return when it comes to light intensity throughout the growth phase.

 

[Delps8]

? isn't that what I'm saying? If I'm giving enough or too much she's not going to have the incentive to grow taller.
If you feed the sweetpot it will stay stocky and bushy and if you keep it out of reach they will follow.

You are 100% correct. My apologies. I didn't read closely enough ("reading comprehension"!).

"it's not going to be incentivised to grow taller" - yes, plants will tend to be short and compact when given adequate levels of light.

I can't get blame it on being stoned.

If you'd simulate a daylight curve with the plants that would have them chasing as well, low power start, build up to a sunny afternoon and then dim down again till night time.. or even just cutting an hour or half hour.

Any research to support that this improves crop yield or crop quality ("crop quality" is the ratio of inflorescence to above ground mass). In all of the research that I've seen, there is no change in CBD, THC, etc. with light levels That's genetic as far as I can tell though, if someone has data on this, please share.

Using basic plant bio — more light = more photosynthesis = more glucose = more growth.

I'd love to see an explanation of how reducing light levels at the beginning or end of the photoperiod would increase crop yield or quality.

One factor bearing on this is that cannabis doesn't need a "dark period". Cannabis is a C3 plant so it does its Calvin cycle processing on demand. Leave a photoperiod cannabis plant on a 24/0 photoperiod and it will stay in veg.

The only discussion I've seen of anything like this was in a Bugbee interview (Dr Growit) when he was asked about ramping up light levels. Growit was taken aback by Bugbee's info on light levels and asked how a grower who was using, say, 600µmol could increase the light levels to, say, 900µmol. He was suggesting that the grower do a modest increase every day.

Bugbee replied that there was no reason to do ramp up gradually. He talked about going from 600-1k in a couple of days and then said that there was no need to "wake up" by saying, paraphrasing, "they're ready to go to work as soon as they jump out of bed in the morning".

 

[Fenderbender]

Any research to support that this improves crop yield or crop quality ("crop quality" is the ratio of inflorescence to above ground mass). In all of the research that I've seen, there is no change in CBD, THC, etc. with light levels That's genetic as far as I can tell though, if someone has data on this, please share.

Oh no.. I'm just thinking that would make them grow a bit taller.
For bigger plants allround you need to increase time no? Just veg them a bit bigger.

I would also think growing taller or short to the pot depends on the amount of canopy for the tent or room and the environment. Some might want to stalk the buds a bit higher and get the buds away from the moisture and bugs of the pots and have some air moving under the canopy.

I personally try to aim for short, but last time with the autos I kept feeding veg & flower for longer in a crossover period and I could tell that in the growth the days I fed the extra veg in the spacing of the buds, plus the days I put them outside where it was very Sunny but Winter and I'm up pretty high and the Sun is pretty low and that made the plants shoot up like crazy as well.. If you light up the stem and internodes they will grow.. and if the source and sweet spot isn't on top they will reach, heck they might even turn back nono the centre of the energy is there! as I've had photos refuse to scrog outside the ideal footprint of a light the buds would just make a U-turn.
And outside the leaves and buds pretty much track the Sun around.

I mean anything will show in the plant.. the light not switching back on time, nutrients, even leaf tucking is kinda aggressive as it completely changes the shape from how it's intended.. as the bottom branches would spread out very wide trailing the fan leaf that covers them.. and just tucking completely changes that behaviour.. amazing responsive beings these plants.

And hmm it doesn't need a dark period.. okay but I observe most growth after a dark period? as you cut the light away and the plant will go hey and go reach.. I'd really like to see this side by side, I think the one with the 24hr light cycle will show constant and wide growth and eventually get bigger but the one with a dark cycle will pulse upwards faster and show periods of accelerated growth in the dark hours is my guess.

 

[Delps8]

Oh no.. I'm just thinking that would make them grow a bit taller.
For bigger plants allround you need to increase time no? Just veg them a bit bigger.

If you want taller plants, you could get a strain of plants that grow taller or keep your light levels low. As you're suggesting, you could veg them for longer, sure. You'll get a bigger plant. If you don't give it much light, you'll have a tall, scrawny plant. OTOH, if you give it a lot of light you'll have a large plant that will tend to have more foliage, more leaves, smaller leaves, more buds, and a higher quality crop.

I would also think growing taller or short to the pot depends on the amount of canopy for the tent or room and the environment.

The environment drives how plants grow. One of the reasons to grow short, compact plants is that you can grow more of them (if you're using racks) because they take up less vertical room, they take up less floor space, they tend to be easier to maintain, and they're easier to harvest. That's just off the top of my head.

I've had grows, autos, that were over 4' tall. Even in my 8' tent, that was difficult to deal with because the canopy disappeared into he top of the tent and the only way I could see what was going on was to stand on a step stool and look in through one of the exhaust ports. There was a huge amount of weed (over 750 gm/m2) but there was a lot of foliage to deal with. And that plant was topped and LST'd (my SOP).

Some might want to stalk the buds a bit higher and get the buds away from the moisture and bugs of the pots and have some air moving under the canopy.

Cannabis plants should be defoliated to promote air circulation, no question.

I personally try to aim for short, but last time with the autos I kept feeding veg & flower for longer in a crossover period and I could tell that in the growth the days I fed the extra veg in the spacing of the buds, plus the days I put them outside where it was very Sunny but Winter and I'm up pretty high and the Sun is pretty low and that made the plants shoot up like crazy as well.. If you light up the stem and internodes they will grow.. and if the source and sweet spot isn't on top they will reach, heck they might even turn back nono the centre of the energy is there! as I've had photos refuse to scrog outside the ideal footprint of a light the buds would just make a U-turn.
And outside the leaves and buds pretty much track the Sun around.

I mean anything will show in the plant.. the light not switching back on time, nutrients, even leaf tucking is kinda aggressive as it completely changes the shape from how it's intended.. as the bottom branches would spread out very wide trailing the fan leaf that covers them.. and just tucking completely changes that behaviour.. amazing responsive beings these plants.

And hmm it doesn't need a dark period.. okay but I observe most growth after a dark period? as you cut the light away and the plant will go hey and go reach..

I'd really like to see this side by side, I think the one with the 24hr light cycle will show constant and wide growth and eventually get bigger but the one with a dark cycle will pulse upwards faster and show periods of accelerated growth in the dark hours is my guess.

Cannabis is the type of plant that does not need darkness for the Calvin cycle to run. The "dark period" is a misnomer but it's embedded in bro science, unfortunately.

 

[Fenderbender]

I'm okay with them running on 24 hrs I'd just expect a different grow shape and behaviour

 

[Delps8]

I'm okay with them running on 24 hrs I'd just expect a different grow shape and behaviour

Only under extreme circumstances. Take a look at grow journals and you'll see a pattern - the tall, slender plants with modest yields have limited light. In journals where the plants are full of foliage and flowers, you'll see better lighting setups.

In the discussions/literature/videos I've read (and re-read), light levels are only mentioned in passing in discussions about plant morphology. I suspect that's because it's assumed that cannabis is grown at or near the light saturation point and they do that because growers want high yield. The only significant discussion is about the spectrum of the light.

Check YouTube videos by Dr. Bruce Bugbee or those by de Bacco (he repackages a lot of Bugbee info). I've attached a paper that discusses the issue.

 

[OldMedUser]

You don't need a PAR meter to keep your plants in the zone. I have one of those little 3-in-1 probes that check Moisture, pH and Light.

The pH part is useless really and the moisture testing is half-assed but the light meter gives me a good reading of the light intensity. The scale reads from 0 - 2000 and I know from years of growing and using it that 500 is good for seedlings, 1000 is about right for good growth of bigger plants but if they are getting tall then I want around 1250 so I get more light further down. If I'm pushing them hard for the stretch with higher temps, added CO2 and higher feed rates then I want to be reading 1500+ on that dial.

I run old school HID lights and almost exclusively EYE Hortilux SHPS bulbs. I know the light quality is first class so all I need to know is how much of that light hitting my plants. Shorter plants are placed on something to keep the canopy even and all the plants will get randomly moved around so they all get their fair share if some have to be out on the edges to make it all fit. I have a light mover to help with wider spreads without going up to a bigger bulb.

PAR meters read intensity too but they only read from 400 - 700nm so don't take in far red or infra red which we all know has beneficial growth effects. Some of the spectrum in their range is not used by the plants at all so if a light is high in those spectra it looks good on the meter but isn't helping the plants grow. That was more of a problem in the early days of LED lighting but all the decent makers are using the right tuning so it's not much of a concern now.

Genetics has more to do with internode spacing and whether you'll have a stubby bush of an indica plant or a stringy sativa. You can influence them a bit with light intensity but not enough to make drastic changes in their morphology. That's most notable when they first sprout and the first couple of weeks of growth than in later stages.

Most strains these days are such mongrels that you don't see as much variation in growth patterns as we used to. Still some but not as much and not as drastic a difference as a lot of old school strains could be.

It's all good tho!

 

[OldMedUser]

I'm okay with them running on 24 hrs I'd just expect a different grow shape and behaviour

With our power costing over 30¢/kwh I wish I could veg at 12hrs/day and flower at 8. I got into autos just for growing outside as I'm so far north photo plants can never finish before the snow flies tho our fall season is getting longer every year thanks to climate change. I won't waste power growing autos indoors and can't grow outdoors any more thanks to hemp farming not far from me now. Planting opium poppies instead this year and see how that goes.

24 hour light doesn't do much for photo plants as they like a rest period and do a lot of internal stuff to get ready for sunup. If growing autos running 24 hours does retard the onset of flowering another week or so then they can get a little bigger before they begin to flower and hopefully yield better. I was surprised how big mine got outside in the ground when put them out a month after sprouting and growing under old T-12 fluoros inside with the wife's tomatoes when they were maybe 6" tall.

This is one of the two in the finished pic on planting day.

The two Mazarilla by Urban Legends with the fans trimmed of in prep for chopping the next day. Monsters compared to how they grew indoors.

Nothing beats that big grow light in the sky and it works for free!

 

[BluNGreen]

Oh no.. I'm just thinking that would make them grow a bit taller.
For bigger plants allround you need to increase time no? Just veg them a bit bigger.

I would also think growing taller or short to the pot depends on the amount of canopy for the tent or room and the environment. Some might want to stalk the buds a bit higher and get the buds away from the moisture and bugs of the pots and have some air moving under the canopy.

I personally try to aim for short, but last time with the autos I kept feeding veg & flower for longer in a crossover period and I could tell that in the growth the days I fed the extra veg in the spacing of the buds, plus the days I put them outside where it was very Sunny but Winter and I'm up pretty high and the Sun is pretty low and that made the plants shoot up like crazy as well.. If you light up the stem and internodes they will grow.. and if the source and sweet spot isn't on top they will reach, heck they might even turn back nono the centre of the energy is there! as I've had photos refuse to scrog outside the ideal footprint of a light the buds would just make a U-turn.
And outside the leaves and buds pretty much track the Sun around.

I mean anything will show in the plant.. the light not switching back on time, nutrients, even leaf tucking is kinda aggressive as it completely changes the shape from how it's intended.. as the bottom branches would spread out very wide trailing the fan leaf that covers them.. and just tucking completely changes that behaviour.. amazing responsive beings these plants.

And hmm it doesn't need a dark period.. okay but I observe most growth after a dark period? as you cut the light away and the plant will go hey and go reach.. I'd really like to see this side by side, I think the one with the 24hr light cycle will show constant and wide growth and eventually get bigger but the one with a dark cycle will pulse upwards faster and show periods of accelerated growth in the dark hours is my guess.

Thank you Fenderbender You get it!
As the originator of this posting and reading the following postings it would seem some either misunderstood the information or just want to give their opinions regarding what they interpreted, which is fine, we are all here to learn and share. So

Regarding the PAR meter, my primary use is to adjust the lights accordingly to have an even light value in my entire grow areas canopy. A PAR meter is not perfect, but it is good to have if you are running LED lights, not so much with HID lights.
I have one of those 3 in 1 meters that you can get for about $12. I use all the time to check moisture levels as a tool to help with watering. For me the other two functions do not work.

I do not want TALL plants, preferably between the sweet spot of 30 -40 inches to maximize the bud growth and capabilities of my setup.

I was inquiring about one plant (Basically every grow from seed) same strain, that is much shorter than all the rest, looks the same per leaf size, shape but is vertically impaired. I have been just putting the shorter plant on a 5 gallon bucket to keep the same canopy height. Historically the shorter plant has about 1/3rd the yield of the taller plants.

I know an old school guy that runs his lights 24 hours a day and that's the way it is and that's the way it will always be. He waters thru a window with a garden hose from his residence and does not believe in PH, flushing or curing.

For me I run 6 hours on and 2 hours off three times a day during veg. This is from trying all the other light schedules to each his/her own. Comments? try it first then comment.

The girls in the photo are now in the middle of week two (11 days) of veg and 24 days from seed.

 

[Delps8]

You don't need a PAR meter to keep your plants in the zone. I have one of those little 3-in-1 probes that check Moisture, pH and Light.

We don't "need" much of anything (Maslow laid that out pretty well) but we make our lives easier by using instruments to measure things.

Speedometers and altimeters come to mind. We do not "need" either of those but I think it's a fair statement to say that our lives are better as a result.

To me, a light meter for growing cannabis is similar. We clearly don't need them but we can do things better if we take advantage of the information they provide.

The nice thing about a light meter (all of $32, delivered) is that it gets you "in the zone" faster, it reduces the chances that you're going to damage your plants, it helps you to maximize the crop yield and crop quality, and allows a grower to grow more consistently.

I'm a strong believer in the adage "You cannot improve what you cannot measure." Sure, you can set up a grow so that everything works just right but if something changes and you don't know what it is then you're ability to react or to take advantage of that change is reduced.

The pH part is useless really and the moisture testing is half-assed but the light meter gives me a good reading of the light intensity. The scale reads from 0 - 2000 and I know from years of growing and using it that 500 is good for seedlings, 1000 is about right for good growth of bigger plants but if they are getting tall then I want around 1250 so I get more light further down. If I'm pushing them hard for the stretch with higher temps, added CO2 and higher feed rates then I want to be reading 1500+ on that dial.

I run old school HID lights and almost exclusively EYE Hortilux SHPS bulbs. I know the light quality is first class so all I need to know is how much of that light hitting my plants. Shorter plants are placed on something to keep the canopy even and all the plants will get randomly moved around so they all get their fair share if some have to be out on the edges to make it all fit. I have a light mover to help with wider spreads without going up to a bigger bulb.

PAR meters read intensity too but they only read from 400 - 700nm so don't take in far red or infra red which we all know has beneficial growth effects. Some of the spectrum in their range is not used by the plants at all so if a light is high in those spectra it looks good on the meter but isn't helping the plants grow. That was more of a problem in the early days of LED lighting but all the decent makers are using the right tuning so it's not much of a concern now.

PAR meters read the PAR range which is defined at 400-700nm. Plants do use light outside that range and the industry uses the appellation "ePar" for that.

PAR includes far red because far red is the term used to describe light at 660nm.

Plants use all frequencies of light in the ePar range. Growers believe that green photons are not used. Research indicates that plants process green photons.

Check out the Bruce Bugbee videos on YouTube. They're about 45 minutes to an hour and he lays things out pretty clearly.

Genetics has more to do with internode spacing and whether you'll have a stubby bush of an indica plant or a stringy sativa. You can influence them a bit with light intensity but not enough to make drastic changes in their morphology. That's most notable when they first sprout and the first couple of weeks of growth than in later stages.

Most strains these days are such mongrels that you don't see as much variation in growth patterns as we used to. Still some but not as much and not as drastic a difference as a lot of old school strains could be.

It's all good tho!

Really good point about getting the plants early. After about a year of growing, I switched from a white LED to separate veg and flower lights. Veg lights sure do make plants short!

For my Spring grow last year, I ran my veg light until day 50 (I'm pretty sure it was that long). Nice short plant but tough to work with. For this grow, I swapped in the flower light on day 33. She's pretty short (9") but not a dense as a year ago.