Light schedule question

[Cornsage]

Greetings and Happy Fall!

After a few setbacks, and a near-catastrophic event (ac vent hose fell and nearly cooked a plant... she came back to life with some serious TLC, and hasn't Hermied as far as we can see! WHEW!) we are finally ready to switch our veggies to bloom.

As we are located in the Midwest, we have been experiencing cool days and chilly nights. Luckily, the sensor in our tent has been registering the temperature as 20 degrees above the outside temp with the lowest being about 60-65 degrees Fahrenheit. from what I've seen, that range is optimal for the flowering stage.

Just one question and I can't seem to locate a sufficient answer: our current 18/6 schedule is 7am- 11:00pm. To accommodate and mitigate the possibility of sudden cold snaps and frosty nights (as the norm has been here in October the past 2 years) Would it hurt the plants at all to switch the schedule from current to 6pm-6am for the 12/12?

We are hoping if the light is on at night will help keep the tent from dropping too low and freezing the plants. We will also have our dehumidifier on, which we've noticed puts out some heat as well which will also provide warmth as well.

Right now they are on a timer, we are thinking that after they shut off tonight, we will then adjust it and keep them in darkness until 6pm tomorrow. But again, Has anyone done this? Did they have good or bad results or are we just overthinking this?

For the record, they are all photoperiod Girl Scout Cookies and our first crop and we have REALLY babied them since starting this in June.

[JohnEmad]

I am not an expert but I would make that small change in time frames for 12/12 and doubt it would have any ill effects. I have done changes like this in the past and the plants have grown and flowered properly.
Wait and see what some of the more experienced growers say about this.

[buds73]

You can start 12/12 whenever is best for you. The 12/12 dark period can be night or day or a mixture of both. From what your saying about temps night time for lights on would probably be the better option. The 6 - 6 schedule should be fine to start. I switched mine a couple days ago, 18/6 times for me were between 7.30am till 1.30 am. I switched mine to 12/12 at 8.30pm. Just be sure that if lights are off during the day that there are no light leaks coming from outside. The way I checked this was to stand inside tent with it closed and had someone with a bright torch go all a the way round tent shining the light at seam areas, vent areas and zip areas.

[Cornsage]

So you think it wouldn't be an issue to have the lights off from 11pm tonight till 6pm tomorrow? That would be 19 hours of darkness. Would that be ok for this one time to change the schedule being that they are photoperiod?

[buds73]

Yes should be fine. Some give there's 24hrs of dark when first switching to 12/12

[OldManGrower]

I have done this with no negative issues.

[Poppa]

At the begging of my reveg grows switch to flowering I had the opposite issue where the heat of days were to hot so I switched to 10 pm to 10 am for my light schedule. Now with the days being cooler I stepped them back 1 hour per day to realign them to 10 am to 10 pm when I'm awake and want to be in the room with them for hours everyday. Last night it got down to 37 here and with exhaust fan running room only dropped to 59 the ambient temps in basement help to keep room from dropping to low. In the spring I did see a few times room dropped to 49 degrees when overnight temps were still dropping below freezing. You can easily change you light period by adjusting by an hour or 2 each day during flowering as long as you keep the 12 hours of darkness between the off and on times I have done this with no ill effects. I would suggest if your going to need to gain access to your grow while lights out you get a green light for accessing during the dark period. The ones I bought VIVOSUN 2 Pack 19-Bulb High Intensity LED Green Light Grow Room Headlight is currently unavailable, sorry.

[Poppa]

I should of also included I am pulling air from outside into the room 24 7 so last nights temps were with the 37 degree air being sucked in.

[Cornsage]

Thank you all for helping with this! it definitely puts my mind at ease when we flip them tomorrow! At 6pm!

[Poppa]

If I was switching to 6 to 6 tomorrow I would switch the timer this evening after 6 pm to go off at 6 am and not come on till 6 pm this would give you 7 extra hours of light before switch as opposed to the 19 hours of darkness. Just to clarify you mentioned using AC are you bringing air in from outside and this is why you have a concern of the cooler night time temps? If your not bringing in outside air then cool or even cold nights should not be an issue.

[Cornsage]

The AC is pulling the air from inside the tent. We have two air intakes on the sides of the tent with filters to bring in the fresh air, so the Air duct is constantly pulling air through, plus the AC pulling air when it kicks on, there is also new air being vacuumed in.

Our concern about temperatures dropping is because our tent is in our garage. The AC is tuned to go off when the sensors register over 80/85 degrees F. So on a normal day, the tent stayed around 75-80s F.

[smoorman]

As I understand it one should always add darkness and not light. This is especially important when plants are in flower. Never shorten the dark cycle. Cut the light cycle not the dark cycle. 24 hours dark when in flower no problem. Extended light is asking for problems although a 1 time event probably won't be that bad.

[Poppa]

I was saying add light to current 18/6 to get lights to go out as they would when Cornsage actually starts 12/12 flower period. I would never add 7 hours of light to a flowering cycle. That being said I have repeatedly added 1 hour to the 12 on but maintained 12 hours of dark before they come back on or the method of 11 hours of light 12 hours of dark to step the light cycle to meet up with my life as temperatures permitted it and have not had any issues using that method. It always depended on rather adding an hour or removing an hour of light while maintaining the 12 hours of dark got my life and the grows day night cycles meshed up the fastest.

[Mr.furley]

You're correct Cornsage just let the timer go off tonight and let them sit in the dark till your new "lights" on time flower schedule it'll hurt nothing. Some Growers practice a 24 hour dark in between veg and flowering stage, things happened in the dark just like they happened in the light.

As far as your Temps, 65f is low enough, when temperatures get too low plants will slow their growth and even shut down so if you can keep it above 65f it would be ideal.

[Cornsage]

From what I read about flowering temps/humidity this seems to be the optimal temperature unless we have a freak temp change (which can happen here).

Anywho, we'll be doing our measurements tonight when the lights come on at 6pm.