You may ask…
Is all “stretch”, or just excessive stretch bad?
Or is it just at certain times it is tolerable and intolerable otherwise?
How do you define what is usually normal growth and what is stretch?
Well stretch is really a good thing, it is excessive stretch that can be bad.
When internode spacing is too large our top bud looks stretched out.
When we have just enough stretch we have a perfectly formed cola over 1 foot in length…ish…
Also when we get too much stretch our top bud is growing into the light and the buds just below get less than optimal light.
Phosphorus
High phosphorus promotes stretch while low phosphorus inhibits stretch.
If you bump up phosphorus when the plant is setting the nodes then all you’ll do is promote stretch via stem elongation.
Phosphorous, as well as potassium and iron starvation, causes increased ethylene production which in turn antagonizes gibberellin action.
The net effect is reduced stretch, lateral root branching and root hair formation, and increases the bud/root ratio too.
But nutrient starvation obviously stunts growth and redistributes the plant’s energy to the roots in order to increase active nutrient uptake and that may be counterproductive with regard to the redistribution of energy into flowering.
The key is to run low P during the stretch cycle only - so roughly first 2 - 3 weeks of 12/12.
Once nodes have set and stretching slowed completely you then bump up P to about 60ppm (although I believe this figure can come down to around 50ppm.
Maybe P as low as 20ppm during stretch, depending on the growth habits of the strain.
This action is not necessary but helpful.
But I wouldn’t recommend this to others yet unless it was just one plant in a side by side test.
I feel we should just keep low P a constant unless we are deficient.
But definitely don’t bump P before stretch like we have been told to do.
The current studies are showing low P reduces stem elongation, but there’s still a way to go in establishing just why this is.
Side note here:
Scientists recently discovered that simple sugars break bud dormancy - it’s long been believed that it was IAA playing the key role but now research has shown it’s primarily related to sugars and the down regulation of IAA plays a secondary role in the process.
IAA plays a secondary role.
It’s second in command but equally important.
I have not found the proper way to use this to our advantage as of yet, but found it in my notes and thought it worth a mention.