Negative DIF and height control

[Radeon]

Anyone have any experience using negative DIF to control node spacing? Just curious.....

[SoOrbudgal]

I'll be the curious one what is DIF?

[Rootsruler]

Are you talking about temp differentials lights on and off?

No idea what DIF means.

[shadycon]

[Bluey]

Differential??

[Radeon]

It is increasing night time Temps and lowering daytime Temps. It's called a negative DIF. Neg DIF keeps plants small and bushy and decreased node distance. Positive DIF (which most cannabis growers use) is cooler Temps at night and warmer during light on cycle. Google it. Used in greenhouses. Or Google "Temperature to control plant height."

[Radeon]

DIF is a greenhouse technique involving temperature control for the purpose of controlling plant internode length and thus elongation rates. DIF's effectiveness has led to a reduction in the need and use of chemical plant growth regulators. Although many common greenhouse plants do react strongly to -DIF, there are some plants which show little or no response to -DIF.^[1]

[Radeon]

Thats from Wikipedia.

[Radeon]

From THC Farmer....

What is DIF? DIF is simply the difference (DIF) between the day temperature (DT) and night temperature (NT) that plants experience where they’re growing. If you put that into a math formula, it would look like this: DIF = DT – NT. Why is that important? Because plant height increases as DIF increases. Here’s how it works: Positive DIF: When the day temperature is warmer than night temperature that produces a positive DIF (for instance, 74F DT – 60F NT = 14F). A positive DIF promotes stem elongation—taller, stretched plants. Negative DIF: When day temps are cooler than night temps that yields a negative DIF (for instance, 65F DT – 72F NT = -7F). A negative DIF suppresses stem elongation—shorter, compact plants. Zero DIF: If there’s no difference between day and night temps, that’s a zero DIF— and stem elongation is intermediate.

[Radeon]

Could a simple temp reversal and topping together increase yield per square foot? That's my question....

[shadycon]

Very interesting.Never to old to learn!!

[No3odiesShad0w]

I think the answer to that is "if the genetics allow it."
There's always a genetic max that you'll hit. Some cultivars may react positively to negative DIF while others may not. If the reaction creates shorter, bushier plants then it's going to look like there's an increase in yield. Is it more effective than other training techniques or environmental manipulations. Maybe a few percent increase? Now you've gotten me curious..... Could be a future experiment I might have to do.

[Rootsruler]

OK so yeah....It's what I thought it was. I just did this on my current grow and it reduced internodal stretch by around 30% - 40% from it's normal stretch.

When I flipped the light schedule I also setup a tent heater to raise the tent temp on lights off a few degrees from lights on temps. I had run the cultivar in the current grow with 2 others as a tester to see how they grew. When I did the tester I ran it as normal with 10° swings lights on/off. The cultivar I chose, Florida Strawberry, doubled in size on stretch.

When I heated the tent, lights off, it reduced the overall stretch and also the stretch between nodes.

You can see the results in my 5 x 5 journal.

Roots Fruits - GrowWeedEasy.com Cannabis Growing Forum

[Bluey]

Without stretch the length of the buds will be reduced as they will run out of room to grow so I would say flower yields would be directly proportional to the amount of stretch, to a point of course.

How can you produce buds like the pic below if it doesn't stretch? In veg my sativas are at most about 12" to 14" high after 2 months of veg. They end up over 3' high at harvest. That stretch is mostly bud.

[Bluey]

I have very small arms according to one person here....lol

Yes, sativa and harvested quite early because I'm not a very good indoor grower and stressed the hell out of the plants with nute deficiency, pH out of range & light stress....but even so....without stretch no way I could get even half of that.

[Rootsruler]

Where I find it useful is in reducing internodal stretching. The reduction in overall stretch is not a concern to me as most of it came in the form of closer nodes rather than reduction of overall stretch. This means that instead of a small flower spaced every couple of inches on the branch I get a full cola. I'm also not concerned with growing giant colas as, IME, they tend to mold easier due to the high water content they hold. I don't have to separate the larger colas from the smaller when drying and curing as most of the colas are uniform in size. The ScrOG method I use has yielded me more dry weight per plant than just letting them grow naturally vertical. Maybe I'm doing something wrong. I also don't need as many plants to fill the sq/ft of the space nor do I need to worry that I'll run out of height.

I'm sure for some cultivars, like pure indicas, it doesn't make as much sense as they are already compact genetically for the most part. Sativas is where I would look to using this technique.

[No3odiesShad0w]

Bluey it's not the size of the hand, it's how well that hand can grow weed 🤔🤣 and by the sound of how things went.. I'd say Nailed it! 🤣

[golfnrl]

I'm planning to keep day/night temps on my next grow as close together as I can just to keep the plants from getting too tall. I recently read about it and Bluey mentioned it as well. Thanks for sharing this. It's helpful.

[SoOrbudgal]

This happens to me because i don't use a extra heat source during winter other than my home heating system. When i lived in the woods all i had was woodstove for 30yrs. I tried using a heat lamp then went to putting the CFL with a reflector in the tent it helped. Really slowed the grow down.

[Radeon]

Would it be productive to neg dif during veg then switch back to positive once flowering starts? Like 2 weeks after flip? I mean it would limit stretch when veg and pre flower, but resume normal positive dif once flowering has begun.

[Rootsruler]

Yes. That is what I did. Once I was satisfied that stretch was done I let the temp swing normally from lights on to lights off. Here's a link to the two journals I got going on if you're interested. The mystery scrog I didn't DIF but the 5 x 5 I did.

https://forum.growweedeasy.com/forum/growing-community/608437-roots-fruits

https://forum.growweedeasy.com/forum/growing-community/611283-2-x-2-mystery-scrog