Lighting requirements on auto flowering plants (indoor hydro)

[ColaDog]

I am gaining interest in auto flowering strains and have read your excellent articles in regards to these types of plants. However, I have not seen anything thus far that addresses lighting requirements. Do you leave on 18 hours until they start flowering? Your response is greatly appreciated. ColaDog

[GanjaGed]

18/6 ( regarded best often ) to 24/0 all the way through. At least that's my take on everything I've read. Never grown Auto's myself.

[D.A.A.S.69]

The one I'm growing right now is the first one I have ever grown. Pistils started showing on day 21 or 22 and i have kept the light on 24 hours a day and I believe she is going to finish a little sooner than the seed bank says . Hope that helps some.

[OzBud]

I grow my autos under 24 hours of light every day. Some seed breeders recommend doing 20/4. I wouldn't do anything less than 18/0.
Don't change to 12/12 for flower, they don't need it and it will hurt yield.

[DrPhoton]

Theres a lot of personal preference with the light schedules used for autoflowering grows. I spent quite a bit of time studying papers and reading comparisons. One paper, that reviewed all studys on continious light, concluded that its benefical use was species dependent.
Every species responded differently, some negatively, some positively. Tomatoes showed a physical distress with continous lighting, others like maize or corn, thrived with the extended schedule. Interpreting the review suggested that the main reason for plants reacting negatively to continous light, was likely due to a plants circardian rythem. The majority of plants that responded negatively to continous light, did not appear to have slowed growth from the extended light schedule, its just that during the dark phase, certain processes run more efficiently.

With the limited comparisons done today on photoperiods with cannabis, the issue is reletively inconclusive. However of the comparisons that i have seen, adding some amount of dark cycles appears to be more beneficial than having lights on continously. Plants have evolved to respond with the natural diurnal cycles of nature, circardian physiological processes are configured with these changes and the overall health of a plant can be dependent on this fluctuation as has been shown in other species of plants. Just because c3 plants do not need dark to survive, does not mean they thrive as well without one.

[berrypilot]

🌱 Great comment!!! I also feel like different plants respond differently. I also feel like plants that are under continuous light are more prone to stress, but I think they grow a little faster. But I keep mine on 18/0 because I feel like I get the healthiest, greenest plants that way, and I'm less likely to run into problems. 🌱

[deezplantz]

Here is my set-up:
3x3 grow tent, two GH waterfarms, Viparspectra PAR 600 LED. i can probably fit four waterfarms in my tent but two is manageable for me now. I'm growing Canuck White Widow autofem with an 18/6 light schedule for the entire grow. I keep the light on a timer and shut it off from 1200-1800 which is the hottest part of the day in my area. I do maintenance when the light is off so the tent is wide open for about 30 minutes in the daylight. This exposure doesn't matter as they are autoflowering. Things are working out well (trouble-shooting a brown algae problem but it's vegging pretty good). The below pic is a few days old. This plant seems to be growing an inch daily and I have to refill my reservoir every other day.

[Sammy]

No rest for the wicked 24/7

[D.A.A.S.69]

Amen Brother

[Weed Pharma]

I have tried many schedules and combinations and use 20/4- not for any of the reasons mention, but for my plants to get the maximum light per day @ 45 moles/m2/day without CO2 (range 25-65) which is considered the amount most cannabis plant can utilize in 24 hrs.

My LED's. Provide that @ 18" for 20 hrs daily, based on indipendent PAR testing which confirms the manufactures recommendation.
i could bring the light closer and get that down to 18hrs daily, but my plants don't respond well- that close and the effective footprint would be reduced.

[DrPhoton]

DLI is an incorrect measuring technique for indoor grows. DLI measurements expects there to be perfect light uniformity in all directions. This is only possible outdoors and this is where the term originates from. If you look up DLI you will see referencing from greenhouse articles. This is because light is lost in greenhouses, due to the enviroment barriers. DLI is used to asses total light in outdoor enviroments, to conclude wether enough light has been reached and wether supplemental lighting is required.
Indoors, light is not uniform, light measured in one spot, is not the same in another. The measurement you are taking is not even accurate because it assumes uniformity horizontally (Hence the m2 multiplier). So what you calculate as DLI is not accurate.
Plants also do not have a specific max DLI. A plants ability to process light over a certain perioid, is dictated by its maximum photosynthetic rate.

Getting a light as close as possible does not improve yield as well, infact it can make it worse.
I cover this here

Your LED seems good though, i estimate around 700mls at the cannopy. Thats about where i have mine also.

[Weed Pharma]

DrPhoton, This is great information, especially for LED users, as the "close to the light as possible" is the demise of many grows.
I still screw up once and awhile, ( most recently when growing under a new LED light) but recognize it early enough to recover, yields still suffer.
I shoot for around 700u/moles in flower and about half that during veg.
If you notice commercial grows generally set the light once and measure 520 u/ moles at soil level!

[DrPhoton]

Yes, the common commercial light configurations was the very reason for me questioning light height. I then proceeded to learn light physics and plant physiology to understand the reasonings. Was not too long before i understood why. I think understanding light physics is probably one of the very most importent keys to utilizing light energy as efficiently as possible. Because you are at least limited by your light source.

Glad it helped. I hope to circulate this around the forum as common knowledge. This alone would place us ahead of most forums due to this common misunderstanding.

[ColaDog]

Thank you everyone for responding to my question regarding lighting requirements on auto flowering plants. It seems to me that a person can be safe to assume that the 18/6 can be used without any significant problems. I always like the idea of resting my plants from the light for at least 6 hours. They need rest too!

[Gears]

I'm a rookie at this. Lighting has been the biggest issue I have faced so far. I badly stunted my first auto by not providing enough light in the early stages. It wasn't the length of time. It was the intensity. Heeding the warnings of damaging seedlings with too much light, I chose to keep my source too far away. The plants never recovered from that. My latest is doing amazing in it's first week under much more intense lighting than my first had

I'm 18/6 for two reasons.
1 - To keep the heat down during the day. Even though I'm using a combination of LED and CFL's, the temps still rise pretty dramaticaly in the grow room
2 - I live in a place where the politicians have driven hydro rates through the roof with, ineffective, ill conceived, idealogically driven "green energy plans". Hydro has become a luxury.

[tyler_ hobbyist]

I personaly run autos 24/0 with leds,hps and mh I have seen upwards of 3inchs of growth in 24hours when running 1000w hps at 15inchs with co2 and proper feeding. Yes hps also makes ur plant strech more but iv still seen autos grow that fast with 24/0light in soil/fabric pots

[ribbitt]

I am on 20/4 they seem to like a little rest my third grow one month two days from start of germ diesel matic back right,kings kush back left front samsara ultraviolet has iWork genetics just in preflower have roped diesel matic trimmed big fan leaves