Avoiding Nitrogen during flowering: Is this just a fallacy?

[TheMoose]

Hey everyone. I read this statement a lot wherever I go, and people seem to preach it almost religiously. That 'nitrogen during flowering should be drastically reduced or completely cut out'. I hear people giving advice like avoiding fertilizers and additives completely because of trace amounts of nitrogen, "which is bad for a flowering plant."

There's also a million different reasons people use to support this theory. People will tell you that nitrogen present during flowering will: reduce the size of your buds, affect the taste/smell in a negative way and cause excessive 'stretch' in the buds making them fluffy and elongated. Some people will say it's just "bad." My experiences go completely against this. In fact, I advise to cut out nitrogen completely if you want plenty of yellow leaves, lack-luster bud growth and a weaker plant that are less vigorous and not able to repair breaks and cuts as efficiently.

I do almost all of my growing outdoors, in the ground and in modified Hempy-style buckets. By a rough side-by-side comparison, the plants with the most nitrogen during flowering are by far the biggest and most vigorous. They look like they are going to fill out better and they look healthier overall. Plant Senescence seems to have been prolonged, consequently holding of Abscission (falling of leaves), and the buds smell just as sweet if not more than their mothers and counterparts. The additional benefit is the yellowing is reduced so they are also less visible compared to plants fed with little amounts of nitrogen. Ideally I like to time it so that nitrogen starts running out in the last week of bud production.

Anyone have an opinion on this? To me it just seems weird that this would be beneficial. Plants grow in the ground, and have evolved to do so since the dawn of time, and there has always been sufficient amounts of nitrogen available.

Depends on the plant really. I think they need nitrogen in early flowering but with longer flowering sativas excess nitrogen can lead to some hermie issues.

[TonyG]

I agree with coop. Depends on the strain. Most plants I have grown did like some N 4-5 weeks into flower. Some just dont need it though and adding to much resulted in stretched out plants add bad node spacing. My experience. Peace.

[TheMoose]

Originally Posted by TonyG

I agree with coop. Depends on the strain. Most plants I have grown did like some N 4-5 weeks into flower. Some just dont need it though and adding to much resulted in stretched out plants add bad node spacing. My experience. Peace.

Interesting, I find that plants with higher levels of nitrogen have better growth overall and not in a way that is detrimental to bud size either. I get more fan leaf growth and a 'bushier' plant with less gaps and under-developed nodes and bud sites.

It's worth noting that I grow mostly Sativa dominant plants. The large majority of them being Haze-based and from Shanti. I have never had a hermaphrodite to date either.

[TonyG]

I do agree with you, moose. My plants that like nitrogen grow just as you described. Which are mainly indicas in my garden. Ive just got done experimenting with so many hybrids from every commercial breeder under the sun.(in terms of promoters like GHS). I feel bad genes have been part of my problem while searching for keeper strains. The sativas ive grown that dont require much N grow a little on the stretchy side when I add a liitle to much. On top of that its easy to overfeed sativas, as I am sure you know, and I have been trying to use the soil mix when transplanting to flower as my main source of N. Im just diving into Hazes and MNS strains for the last 8 months. Damn, I have a ways to go still. Good to have you in the community.
Peace.

[Jimmy The Gent]

Adequate Nitrogen is what is required.

Depends on the strain.

I agree on the point that insufficient N fertilisation leads to poor growth and as such poor yields.

[TheMoose]

Originally Posted by Jimmy The Gent

Adequate Nitrogen is what is required.

Depends on the strain.

I agree on the point that insufficient N fertilisation leads to poor growth and as such poor yields.

I guess adequate/sufficient is the magic word. Since these are subjective terms, it's down to the individual’s interpretation. With that being said, I like to fertilize with enough nitrogen to keep all but the lowest leaves from yellowing and falling off for as long as I can. The yellowing and dropping of the leaves is known as abscission and is partially due to nitrogen being relocated to higher (apical) parts of the plant. This is easily observed during oncoming and peak of flowering.

The hormone Ethylene is responsible for the promotion of abscission and effectively ‘tells’ the plant (for lack of better words) to do so, by overriding other hormones such as Auxin and Cytokinin. Those hormones are responsible for splitting and elongating cells (increasing mass of the plant as well as any recognizable growth). Auxins and Cytokinins also force or promote the storage and concentration of nutrients in the apical (Auxins) and lateral (Cytokinins) leaves, buds etc. For example, think about why the tops of plants are always greener and more vibrant.

Auxin’s, which actually work against abscission and have proven to completely stop it in some plants. They are produced and found in the highest concentrations at the very tops of plants. Auxin’s promote every type of growth (besides lateral) at certain concentrations, as well as forcing nutrients to the respective areas that they are most concentrated. When the concentration of Auxin weakens (starting from the very lowest points of the plant), cells become more sensitive to Ethylene (a natural gas-hormone responsible for ripening/rotting fruit), which triggers the acceleration of senescence (aging) and in term abscission.

As for a quick note on Cytokinin: It is a direct rival of Auxin in that the balance between the two stimulates different types of growth. If the Cytokinin: Auxin ratio is more prominent on the Cytokinin side, lateral growth is allowed and your lower branches will all grow freely. If the Auxins overpower Cytokinin, you’ll notice your plants will have little leaves/shoots known as ‘dormant buds’ that don’t start growing.

So if you’re still reading, you will be wondering what any of this has to do with nitrogen during flowering. Basically I just wanted to lay down a foundation before elaborating on nitrogen's role in all of this. You’ve probably heard that high levels of nitrogen can ‘prolong the onset of flowering’, which to me makes sense.

Here are a few facts about nitrogen and plants:

• Nitrogen combines with other elements such as Carbon, Hydrogen and Oxygen etc. to form ‘Amino Acids’.
• Amino acids form protoplasm, which facilitates “cell division” and consequently the potential for plant growth and development
• Amino acids are considered the ‘building blocks’ of protein
• All plant enzymes are made up of protein. Enzymes are considered catalysts for all chemical conversions within a plant, therefore the successful functioning of the plants ‘digestive system’ , hormone synthesis and general function
• Nitrogen is a crucial part of chlorophyll and necessary for photosynthesis (your buds might be coated white, but they’re still green underneath )

So with the previously listed points in mind, I’d like to point out that the most common and important “growth promoting” hormones, Auxins and Cytokinins, all contain nitrogen in their chemical structure. If a plant is lacking nitrogen, it will have to disperse its limited supply amongst all of its metabolic functions and may not be able to keep up supply of crucial Auxins and Cytokinins. This is why I agree with the proposal that high levels of nitrogen can delay flowering, because a large supply would likely attribute to the production of more Auxins and Cytokinins, which would delay Ethylene production/dominance.

It’s worth noting that neither Ethylene nor Gibberellin (which is responsible for stretchy, long-distance inter-node growth in marijuana, as well as being used as a foliar spray for producing male flowers (think:hermies) contain any nitrogen in their composition. So, nitrogen is not responsible, at least directly to the synthesis of these two hormones. This is why I am skeptical about the idea that excess nitrogen causes ‘hermies’.

Well that’s a lot off my mind anyway. Hopefully I haven’t shared any incorrect information, if so correct me. Over the last few weeks I have spent A LOT of time reading over Biology books and websites, particularly trying to grasp every bit of information I can on hormones and plant growth.

[wonkadonk]

Certainly N is needed in some quantity in flowering for a healthy vigorous plant. My experience with too much N is a bit too much stretch and too much leaf in the buds. There is definitely a sweet spot. Enough, but not too much. This might vary quite a bit plant to plant.

[SCARHOLE]

I agree, we shouldn't stave our plants of food in flower.
I also see no difference in taste when i quit flushing an starving em.

Originally Posted by TheMoose

It’s worth noting that neither Ethylene nor Gibberellin (which is responsible for stretchy, long-distance inter-node growth in marijuana, as well as being used as a foliar spray for producing male flowers (think:hermies) contain any nitrogen in their composition. So, nitrogen is not responsible, at least directly to the synthesis of these two hormones. This is why I am skeptical about the idea that excess nitrogen causes ‘hermies’..

other plants - but nitrogen levels definitely play apart with abnormal sexual flower production.

"Uriu (1953) demonstrated the role of nutrition in olive
pistil abortion. His observations that high leaf/¯ower ratios
and nitrogen fertilization promote hermaphrodite ¯ower
production agree with the trend toward femaleness in other
andromonoecious plants growing under favourable environmental
conditions (Primack and Lloyd, 1980; Solomon,
1985; Emms, 1993). Hence, the high variation observed in
olive in the proportion of staminate ¯owers among years,
trees, branches, shoots"

"Significant gender 3 nutrient interactions for root fraction and whole-plant
nitrogen concentration indicate greater nutrient stress in hermaphrodites than females. Hermaphrodites also acquired less
total nitrogen than females. Nutrient limitation contributes to opportunity costs of male function, but there must be other
contributors. Possibilities include limitations in other resources, gender effects on morphology, and genetic trade-offs not
directly involving allocation or morphology."