Veg & Fruit Cycle: Peppers

gringojayJune 18, 2009

The vegetative growth & fruiting cycles of peppers is not purely a fertilizer relationship. ( Post "Nitrogen Concentration for Pepper Plants, 15 June, 09 spins off these comments.)

Pruning plays a tactical role in intensive (less practical in open field acreage) commercial pepper operations' yield.

Young transplants are ideally pruned progressively, so that allow enough leaves to coordinate with few stems, in order to get a continuous yield once fruiting has initiated.

If neglect ongoing pruning the result is spurts of vegetative growth & then the fruit bears in flushes. A rhythm of sequential pepper flushes makes it difficult to tweak (selectively prune) the plant stems & leaves back into a highly productive synchronization.

After a fruiting flush the lapse into vegetative cycle means that ultimately the total yield will be reduced.

Pruning is also relevant to getting some peppers to bulk up & mature; in this instance it is the fruit itself that is pruned. When it is too hot, reducing the fruit load allows the leaves enough margin to deal with their environmental stress.

But, in all instances (normal conditions or high heat) always keep some peppers on the plant, until the next flowers come open. Otherwise the plant will drift back into vegetative mode & continuous cropping is lost once again.

"Bloom" inducement proponents often emphasize Phosphorus fertilization boosts. Yet, if commercial pepper data is correct P use is kept constant (say 50 ppm).

There is a case to be made for reducing Nitrogen to shift the plant out of vegetative mode. In commercial production the goal is to maximize the productive life span of the plant & cutting N a tactic with consequences.

Home (USA) growers are often annoyed that choice peppers from Mexico & New Mexico flood the supermarkets. While these are hot climates their desert like weather includes night time temperature drops.

Temperature factors for peppers can be simplified as follows (the small hot tropical varieties are obviously adapted to heat differently).

The 24 hour average air temperature has the most impact on pepper fruit & it's ability to promptly ripen. If this average is too high it tends to keep vegetative processes going. ( For reference purposes: when Bell pepper plants are developing vegetatively this 24 hour "ideal" is 21*C or 70*F - 23*C or 74*F.)

In addition, the influence of lower night temperatures & warm days is to trigger flowering & induce fruit set. (For reference purposes: when night time air is 16*C or 61*F it is good for Bell peppers.)

(Peppers, like Bells, that yield poorly in day time temperatures over 32*C or 90*F are suffering from physical distortions induced in the flower structure & few fruit overcome that developmental problem.)

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could you please better explain what kind of pruning you propose to do to peppers? The plant that is, not the fruit.

    Bookmark   June 19, 2009 at 1:24PM
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Hi grizzman,
At about 6 weeks a seedling will have 4 true leaves & be ready to transplant; it can have 2 - 3 stems.
Prune seedling to only 2 stems (in a Bell pepper these can then grow to over 12 feet or 4 mt., if supported). Allow the plant it's vegetative development & see explanation (farther below) on pruning side shoots, once they develop.
To shift vegetative growth into mature fruit productivity (later on) pruning will essentially be an ongoing tactic, done 2 times a month. This keeps pepper plant from yielding in flushes & relapsing into vegetative growth.
No reduction in adult plant fertilizer Nitrogen & no increase in Phosphorus is used; a large plant needs it's N & extra P can cause problems that impact on yield.
When the plant begins to put off side branches from main stem nodes it is time to begin pruning vegetative growth. Each node on the 2 stems of the pepper plant gets all it's "excess" leaves pruned off it, so that just a single (1) leaf remains at each of it's nodes (ie: main stems have 1 leaf at every node).
Later on, when plant is about 4 months old from seed ( & after some leaf pruning on the side branches, which is explained shortly) you can let a 2nd leaf grow out at each node on the main stems (ie: 2nd leaf/node by then will not push plant back into vegetative mode).
The plant will likely be fruiting at this age ( when keep 2nd leaf/node) & needs more photosynthesis to bulk up the fruit. You want to take plant into fruiting mode progressively & have those hormonal signals stabilize.
Since you are trying to control the plant there is some strategic early flower pruning, to get fruit set occurring how you want it synchronized to lock in that hormonal shift.
In the crotch, or fork between your 2 stems, pinch off that flower. Likewise, going up each stem you pinch off the flower (if any) at the 1st node above the fork.
What you want is to stagger the first 2 peppers on each stem & allow the plant to definitively transition into a continuous (not flushes) fruiting cycle. The plant is made to "work" to replace the lost flowers & this helps condition that response. It is not a question of giving it more time for vegetative/root development to make a better plant; it is a tactical sacrifice that means more total productivity.
So, after pruning the 1st flower that develops above the fork, let the next higher flower grow & set fruit on the 2nd node of each of both main stems. Then, get rid of (prune) the flower at the 3rd node of each stem.
At the 4th node on each stem you stop pruning away any more of the main stems' flowers. (If your plant suffers an "accident" & loses it's lowest flowers then just start the pruning sequence of no flower/yes flower/no flower/yes all subsequent flowers where you can on each stem.)
Returning now to keeping vegetative growth under control.
The plant will put off side branches at each of the nodes, on both main stems, for as long as it is growing. These are to be controlled, as they develop at any age, to avoid pepper plant getting bushy.( Yet keeping some minimal leaf growth for photosynthesis & preventing the sun burning the pepper fruit.)
As a side branch develops (when it starts is not important) it is is important that each side branch is dealt with before it's vegetative growth begins to send growth hormone signals. And, please do not confuse a side branch tip with the tip of a main step (do not cut off either main stem apex or plant will only be bushy.)
On each of the growing side branches (not main stem,now) you want a leaf to develop at it's (the side branch's) very own 1st node. Once you see a leaf point of growth, prune the side branch back to it's 1st node (ie: side branches get to stay & keep a leaf at a node, but can not have a 2nd node for their own continued bushy growth).
The only thing to add (about side branch technique) is, that about 4 weeks after you have pruned a side branch back to it's 1st node (& left it with just 1 leaf) it is good to let a 2nd leaf come out & remain (on each side branch). By originally holding down the number of side branch leaves to only 1 it keeps the vegetative cycle from resuming.
After a while there is no side branch vegetative hormonal signal when you allow the 2nd (& no more) leaf at it's first & only node. It is preferable to have that extra photosynthetic capacity & the leaf cover for a pepper crop that is commercially planted at the density of 1 pepper/ 3.5 square feet (1 pepper/ 0.33 square meter).
One final look at the main stem (only): you pruned it to 1 leaf/node ( when got side branching), let it have 2 leaves/node (at +/- 4 months old, fruit growing). If a plant is getting a lot of sun (or peppers are planted far apart) you should let a maximum 3rd leaf at each node on both the main stems develop; it will protect the fruit & deal with factors stressing the plant (this last leaf is not required for photosynthesis capacity, but those side branch leaves are).

    Bookmark   June 19, 2009 at 6:29PM
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Many induce flowering by shifting fertilization to high Phosphorus (P) "Bloom" formulas.
Tissue analysis of plants show the extra P is not showing up in the plant & of course it is not destroyed or excreted by the plant.
With all nutrients there are minimal levels required to prevent deficiency, broad ranges of sufficient amounts for each & a toxicity level (where too much of a good thing is bad).
High P fertilization, even though it is not an excessive amount, will stymie the uptake at the roots of Copper (Cu) & Zinc (Zn). The end result (of boosting P) does not necessarily provoke a deficiency of these trace minerals, but it does alter the previous levels of these trace minerals inside the plant.
Prior to inadvertently lowering Cu & Zn (Iron is likewise less absorbed, but not subject of this post) these trace minerals were "sufficient", performing their functions at a certain rate & the plant was growing vegetatively. When their amounts drop it is their level (or degree) of function that shifts & this triggers stress (ie: plant signals itself that it is time to bloom, while it still can & get on with reproduction).
Cu is involved with electron transfer in the photosynthetic process, but it is the enzyme compound it forms with Zn that is relevant here. The enzyme is called Cu-Zn Super-oxide-dismutase (Cu-Zn SOD).
Living processes, people & plants, spin off free oxygen that can act in a radical fashion; akin to burning (oxidize) things inside. SODs give oxidation protection, meaning Cu-Zn SOD is important for oxygen biochemistry.
So, by inducing a drop in Cu & Zn the plant that is growing starts to experience more internal damage, which is a stress that is acted upon (like a call to action for seeds to self perpetuate).
Cu-Zn SOD is an enzyme that also helps regulate the signal called Growth Factor (GF) that a plant puts out. In this role it regulates the plants capability to react to signals (like GF) from the cells.
Enzymes exist in 3-dimensional space & can fold or unfold (so to speak). This makes the amount & what type of protein surface that the enzyme is exposing to a binding site be variable. Cu-Zn SOD controls some genetic expression of other proteins that then themselves signal the plant what to do next; it can become a cascade of different events (vegetative or fruiting).
For a plant performing at one level of Cu & Zn to be forced (by high P) to function at a lesser level of Cu/Zn (even though trace minerals are statistically "sufficient") there are hormonal changes. Vegetative GF is still attended to, but there is a shift that accelerates "bloom" GF.
As for the down side, the obvious is high P building up in the substrate & causing TDS complications. Less obvious is the diminished Cu & ZN uptake; which means Cu-Zn SOD induced GF distortions (fruit rots black on the plant) & oxygen radicals poorly neutralized (plant tissue ages so productivity less than optimal) .

    Bookmark   June 21, 2009 at 12:55PM
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Edit correction, "Vegetative Cycle Control" 2 posts up in this thread:
paragraph starting "As side branch develops ....".
2nd sentence of that paragraph read editing "step" to correctly read "stem", as in main stem.

    Bookmark   June 21, 2009 at 9:12PM
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Fruit, flowers & leaves often drop off the plant.
The leaf pruning described above is done regularly to avoid taking away mature leaves, which would set the plant back. (The role of leaves is not subject of this post.)
The plant has a way of dealing with naturally occurring factors. Genes get hyped-up by challenging factors, which cause a hormone (ethylene) to instigate some special enzyme activity. That enzyme alters the cell walls, so they break down at the pre-programed place ( where leaf, flower or fruit can safely drop off).
Causes acting on the leaves that instigate drop (abscision) are generally related to light, how close the plants are & pruning/loss/damage.
Causes acting on the flowers that instigate abscision are generally related to the temperature.
Causes acting on the fruit that instigate abscision are generally related to the number of fruit & where that fruit is.
Pepper fruit already on a plant sends out hormonal (auxin) signals that try to stymie certain new fruits' hormone. This works in a predictable pattern & so should not cause the grower alarm.
The existing fruits' signal is not actively affecting new fruit setting 1 - 2 nodes away & it loses effectiveness by the 6th node up. New fruit aborting (dropping) at 3-5 nodes distant from any developing peppers is usually just from natural hormone domination.
(If want minimal fruit drop then harvest all peppers before new fruit sets. A natural crop bears in flushes, with vegetative spike of course.)
There are, in a season, on going alternating cycles for the pepper fruiting rate on the same plant; it is genetically driven. A growth period of abundant fruit setting all at the same time will then have those peppers mature slowly. The alternate phase will be of lower fruit numbers setting, yet faster maturation of that fruit.

    Bookmark   June 22, 2009 at 6:44PM
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