change light cycle

[Mildred]

Hey all. My plan is half way through the flowering stage and I want to change the lights by 12 hours. I started in winter so have lights on at nightfor the heat. It is now summer and it is hotter when my LEDs are off. Can I leave lights off for 24 hours to swap?

[AGH]

First off, it took me way too long to realize that you're in the southern hemisphere...here in the US we're going into winter :-p

What are the highest temps in the tent when your LEDs are on? Where I live, it gets into the 100 degree F outside and, although I grow in my basement, so it's a little cooler down there, my LEDs never make the tent warmer than 80 or so with lights on during the day.

The reason I ask is because you don't want to stress your plants, especially halfway through flower - you've worked so hard! Of course, if it's getting unacceptably warm in the tent, you may have to make some adjustments, but those might include finding a way to cool the room your tent is in, etc.

Let us know and then we can make some more suggestions for you!

[Mildred]

Thank you for you reply AGH. Yes I'm in Aotearoa/ New Zealand. My concern is that the heat conditions are completely visa versa to what is ideal. When lights off (day time) the heat in the room will sit between 73f and 80; depending on how hot the day is. I can control this bit with fan but this drives humidity up. When lights on (nighttime) temps can be between 63f to 72f. With Rh sitting just under 50. Would the shock of 24 off be worst the the last month of girls life experienceing the opposite of the ideal heat patterns?

[AGH]

Ahhh, I see! That's an interesting situation!

How much warmer do you think that it would be with lights ON in the daytime? And how much cooler with lights OFF in the nighttime?

With temps getting up to 80 even without lights, that may end up getting too warm depending on your strain?

And with temps falling to 63 even with lights, it would be even cooler without lights and 65 tends to be the coolest I like my tent to get. Granted, cooler temps (that are reasonable) won't kill your plant, just might make it grow slower.

However temps that are too high, as you probably know, can be very detrimental to plant health and can be a perfect set up for pests and diseases.

I don't think I really have a good answer! I would say, if you're going to change the time the lights are on, do it gradually, maybe over the course of a week. That way it wouldn't be so much of a surprise to them. It's the amount of dark hours that keep your plants in the flowering stage, so keep that in mind if you do it gradually.

You mention 'the room' so I'm assuming you're using an entire room for the grow or do you use a tent? If you use a tent, managing the temp/humidity outside of the tent may be able to help switch those temps around to be more appropriate for the on/off cycle.

If it were me, my first goal would be to find a way to get the temps/humidity in check to be aligned with 'day/night' If that wasn't possible, I'd probably keep it the way it is or if I was going to change it, I would do it gradually. I think that the 'low temp' and 'high temp' limits are really just that and not based on lights. It just so happens that it's usually warmer when lights are on so we associate the high temps with 'day' and low temps with 'night'. But I would think that as long as temp/humidity are at the correct levels, it should probably be okay. With lower temps during the 'day', you might just get slower bud development...just thinking out loud!

Sorry to not have a definitive answer, but that's part of the fun of growing! Keep us posted with what you decide and how it goes!

Maybe someone else has some thoughts to share!

[3Berries]

You can change the time no problem. Just maintain the 12/12.