Interesting. The conventional wisdom from most everyone has always been that red and, somewhat recently, far red are essential to a good finish.
Please explain the biology that goes on when you do this. I've always been taught that excess blue spectrum in flower will promote more leaf growth.
Yeah so there's a lot that goes into this from where it started to where it is today.
In regards to plant biology, marijuana naturally shuts down leafy veg production and cuts food to leaves around week 5-6 of flower, directing all energy to flowers, which opened the door to experiment with unconventional lighting the final weeks.
Commercial growers looking to one up the next grower stumbled on this and it led to products in nutes and lights.
Designer nutes were effective but really unnecessary because the plant cuts off nutes to leaves anyways when it begins to ripen (yellowing bottom leaves during ripening stages feeding upper growth) but something like H&G Shooting Powder was designed just for that stage of life ensuring a great calyx to leaf ratio at harvest but did nothing to increase potency.
The better option was to use lights and sometimes environment working with cold nights and warm days. All genetics dependent.
In lighting we saw dual lamp reflectors for HID come out. Those were by demand so growers could run a MH lamp with HPS in the same reflector and blend the spectrum.
That was the first domino to fall in regards to the old idea of 2400 kelvin for flower and 4200 kelvin for veg becoming outdated.
Growers found that by blending the two spectras to around 3000-3200 kelvin, it could produce weight but also increase potency of a crop. And that is where CMH entered the arena not only getting those results but offering the performance using less electricity to do it. Basically 600 watts of 3100K CMH could outperform 1000 watts of HPS+MH.
Additionally, horticulture LED came to market and some lights were flashing very potent weed but lacking weight. With that, the early days of LED for cannabis was largely regarded as a supplement light that could do great for veg but lacked performance in flower with the exception of resin production. The LED grown buds were small but way more potent than those under only HPS.
HPS + MH was ideal for an increased potency but with LED, we could get that blue but use a lot less electricity getting it. Then LED got better and better to a point where it could go toe to toe with HPS and deliver weight and potency.
Where LED excelled was with the blue spectrum it could hit. That 420-460nM was the sweet spectrum to have along with the red that stretched from 700nM-1000nM range.
Some LED on the market, Cree COB for example, were a step backwards because they lacked the wide range of blue. Things kinda went back to HPS performance with that light. Only difference was that Cree could do what HPS could at half the power cost but could not increase potency. It's the lights with that wide range of blue that could increase potency so today we're seeing a lot more blue and white diodes in fixtures with the reds.
Somewhere along the line going back only a few years ago people started adding UV to LED, mostly due to COB under performing in blue and UV.
Today however, diodes are better than those Cree with Osram and Samsung leading the charge. So today not only can we get powerful LED with a strong output of blue nM, but we can also add UV to that mix and hope to grow even more potent weed than ever before. Sometimes it works great with reports of 50% potency increases and sometimes there's no difference at all. There's a lot of variables to getting it to work with the first being genetics.
And it doesn't stop there. Increasing red output early on during germination and veg is known to increase root development so that old idea of 4200 kelvin for veg is getting more and more obsolete. Sure it works as all the old ways still work well but there are advantages to mixing it up a bit and it resulting in a better harvest at the end.
For me personally, I use a lot more red than usual for veg and a lot more blue to flower than what I was doing 10-15 years ago all due to experimenting with it and seeing better performance from it.
When it comes to weight and doing things to increase it, I tend to rely on genetics and the abundance of red to far red in my lights.
I focus on the roots and along with that red and good genes, the weight will always be there at the end.
But potency is another animal and that's the creature I'm always trying to elevate and definitely prefer something like lighting to do it rather than any kind of sweetener, terp enhancer, or bloom booster fed to the roots. What I've found is that I'll always want some intense 420nM-460Nm blue at the end with no worries of poor leaf to calyx ratio and lack of density has never been an issue.
Still undecided on UV, mostly the delivery of it, but if something like lighting can increase potency I'm usually one of the first in line to give it a shot so I continue on with my UV experiments
