Best to keep your lights in the established PPFD range. Prolly need a cheap PAR meter that measures PPFD. Not rocket science or anything. Requires stuff like hanging height and light intensity adjustments. It don't have to be exact as long as your plants are happy

Environment, Co2, Nutrients, Genetics, etc is going to determine how much light a plant can take.

Nothing can substitute being able to read what the plant is telling you.
I use ppfd meters only as a reference tool and for record keeping, helps when transferring plants to another tent and gives a good baseline for other grows but not necessary IMO.

Never adjust lights too much at once, only 1 level at a time and wait and see how they respond before adding more.

IMO, less is more during veg. From a full spectrum led, 30%-40% in veg at 30". When plants grow to 24", I move back up to 30".

Instead of moving the lights all the time, I've recently started to leave my lights at top of the tent and use a higher intensity and then lower the intensity as the plants grow toward the light.
Lights might be at let's say 65" high, running at 60% intensity. When the plant grows to let's says 50", I'll lower light intensity to 50%.
The light being higher and at a higher intensity helps keep the tent nice and warm, especially important during germination, seedling, and early stages of veg.

In flower I cycle light intensity, explained in article below.

OldSchoolest said:

Better to give it more than it needs

OR

Better to take the Goldilocks approach and stay at or under the juuuuust right

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I would choose door number two. I increase the light intensity according to the life stage of the plant, like @NoVC01's chart. Once the plant is established, I increase the light intensity till the plant complains, then I decrease it till it doesn't. The exception is I use a humidity dome for starting seeds that has its own lights for the purpose. That said, my main intent is to grow healthy plants, and that means providing all the growth factors in optimal amounts.

Thanks for the class I'm lucky my tent has 3 lights that I can adjust the % of red white blue individually from 1% to. 99%. Long time grower without aid. Just started PPFD as a approximate guide. I reverted back to my original settings, raised the lights to 40" from top of container. Checked PPFD was close enough in the garden.

LoveGrowingIt said:

I would choose door number two. I increase the light intensity according to the life stage of the plant, like @NoVC01's chart. Once the plant is established, I increase the light intensity till the plant complains, then I decrease it till it doesn't. The exception is I use a humidity dome for starting seeds that has its own lights for the purpose. That said, my main intent is to grow healthy plants, and that means providing all the growth factors in optimal amounts.

Click to expand...

Ooah ooah dome low light intensity too!

OldSchoolest said:

So.

Do you guys think that it’s better to slightly UNDER light your plants vs OVER lighting them?

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The length of the day is predicted from the very beginning. The intensity is provided. With a stable balance in the root zone and based on these parameters and genetic characteristics, a harvest is predicted. Apparently so. Considering that the plant has such a difference in development at 12 and 17 o'clock, you can try to compare it. But first, steady balance!

In fact, there is a feedback loop. Stable condition of the roots in terms of access to the elements will give the plant an advantage. And environmental conditions, if they do not violate the genetic capabilities of the plant species, perform the function of limitation. This is only true for indoor cultivation. Only in this case, the plant's reaction to lighting is manifested, and the yield will be limited by gas factors. Lighting is a deep topic, and besides, it works with gases, with water vapor and co2, as well as with the spectrum. Only in case of stable root balance! With intensive processes, oddly enough, time increases, expanding the boundaries of the plant. It's more convenient for anyone to control, but in fact there will be a winner, you just need to compare. Try it)

Nature has a very simple task - to do it as quickly as possible)18 and 24 hours are not a problem for cannabis, the problem for it is the sterility of the dark phase.Both at the stage of growth and at the stage of flowering. When the light threshold is exceeded, the daytime phase of photosynthesis begins.If you pay attention to the fact that in many countries it is not the harvest that is limited, but the number of plants, then we can assume that this is what limits yields.

Very few people can keep everything on point enough to where the light is the bottleneck. If you increase the light, you will have to proportionally increase the food, water, and the temperature. At a certain point, usually around 900-1200 ppfd, co2 becomes the bottleneck. But everything must be kept in proportion, or you will start to see burnt edges, tips, discolored leaves etc.

It’s strain and environment dependent, but the chart noVCO1 posted is a good starting point.

In hydro supplemented with CO2 and heavy feeding, I’ve gotten the lights up to 1400 PPFD and thriving.

I look for taco leaves, bleaching, foxtailing, etc. and lower the lighting if needed.

Most plants in coco without CO2 do well between 800-1000 PPFD. That is my baseline.

Also depends on if the plants were acclimated to intense light in veg. A plant vegged under 200-300 PPFD need time to ramp up. It’s a common issue.

I ramp my vegged clones up from 250 to 600 during the first 4 weeks of veg, then flower starting at 650 to 800 in the first 3 weeks of flower.

You have to be careful because it’s all dependent on variety, feeding, and CO2. Too much light without proper feed will cause issues. Too much feed with low light will cause issues.

Once you get into humidity, ambient temp, root temp, CO2, and foliar feeds… then the plants tend to want more light.

I’ve flowered successfully ( dense, potent, dank buds ) using 750 PPFD max. There really isn’t a single solution other than examining the plants, collecting data, and doing multiple runs of the same variety until you have it dialed in.

Even then, there are other considerations (grow style, supplements, light spectrum, etc ) to explore and maximize expression.

Here is one of our strains, La Toxica (MK Ultra x unknown 00s NY Sour Diesel) grown under 2 very different conditions.

One is sun-grown using organic no-till method (mostly build-a-soil method), and the other is using REMO synthetics under LED at 1000 PPFD max with CO2 in coco. Notice the extreme difference in final product.

Wish you could taste them both! Very different in look, color, smell, density, and flavor! I prefer the indoor smoke, but love the look of sun-grown natural beauty. These are both clones grown from the same mother plant!

DLI for stage of growth is what I'm looking to set. I focus on distance from canopy for coverage and heat management, and DLI. I take an average of the most intense zone (usually dead center) and the weakest zone(s) and go with that, also moving plants around if possible so all can get their turns in the hot zone(s) for a while.