When & How to Use CANNA PK13/14
Exclusive Q&A Part 1 – CANNA x The Greenhouse Effect
Welcome to the first in our new Q&A series with one of our leading fertiliser brands, CANNA.
In this series, Nico from CANNA will be answering some of the most common questions we get asked by growers relating to their popular range of nutrients & additives.
To kick off the series we are going to look at when and how to use CANNA PK13/14…
When and how to use CANNA PK13/14
There is a short answer and a long answer to this question…
With both answers, bare in mind that every different type of plant will have a different window of application.
The exact time window can vary not only on the differences seen between the genetics of different plant types (short flowering times Vs long flowering times), but also environmental conditions of the growth phases up to the point of application.
Meaning, that even with the same plant over multiple cycles, the ideal window of application can change slightly. As a grower, you need to develop your greenthumb and keep a close eye for signs from your plant during the generative cycle. Over time you will develop more familiarity with your plant and will eventually see it ´telling you´ it is time to dose PK13/14!
The short answer:
Roughly 50-60% of the way through the generative period, there is a demand from the plant for an increased ratio of Potassium and Phosphorous than what is provided by the base nutrients for a short, one week period.
For example, a photo-periodic plant with a eight week generative cycle would require application during approximately week five to six of this period, for one week only.
The maximum dose rate we recommend is 1.5ml per Litre. However, depending on the health and condition of your plant at the time, you may not need this maximum dose rate.
PK13/14 is a highly concentrated and powerful PK booster, so if your plant is already suffering from symptoms relating to nutrient deficiencies and/or low pH issues then it may be wise to use a half or quarter strength dose.
So, 50-60% through the generative cycle (roughly week 5 to 6 of an 8 week period), dose CANNA PK13/14 at a maximum dose rate of 1.5ml per Litre (or less depending on plant/substrate health).
The long answer:
We formulate our base nutrients to provide everything needed by a plant to achieve a fully-fledged harvest.
However, when fast-flowering plants are performing particularly well during the middle of their generative cycle, there can be a brief period where applying an elevated ratio of potassium and phosphor can push an already developing plant to its natural limits of nutrient uptake and flower production.
There are a couple of ways to identify this period, and also ways to deduce what sort of dosage you would be best applying, rather than just going in at the maximum 1.5ml per Liter rate. Understanding the how´s and why´s will give you a much better understanding of exactly when and how much to apply.
Key things to consider when determining the best approach for using PK13/14
1. Nutrient requirements
2. Appearance of plant
3. pH of substrate
4. Nutrients deficiency symptoms
We will look a each one of these in more detail to get a clearer picture of the best application.
1. Nutritional requirement changes.
As a plant goes through its Generative cycle
If we have a look at the average requirements of certain elements, then this gives us the first insight into understanding the exact time.
The above two graphs show the average change in nutrient demand over the duration of a crop cycle. The graph on the left represents Nitrogen and the graph on the right represents Phosphor. The blue lines are what a plant would ideally require. The red lines represent what would be delivered on each irrigation by the grower.
You can see the change in phase cycles as the graph goes from left to right, the plant moves further into its flowering phase. The use of Nitrogen stays relatively flat throughout the whole life-cycle, tapering off slightly towards the end of life. The use of phosphor (and potassium) increases almost exponentially during the same period.
The section where the blue line goes above the graph is where the plant demands a higher ratio of P and K for a short period. This is where PK13/14 should be applied alongside our base nutrients, being formulated to precise ratio´s in order to work directly alongside one another to help drive a plant to its natural limits. It is only a small window of time where PK13/14 is require as an extra to our base nutrients
2. Appearance of plant
This is one of the best ways for a grower to establish when is best to use PK13/14 as it is typically the result of experience gained from repeatedly growing the same type of plant over time. A keen gardeners eye will see the plant telling them it is time to dose PK13/14, by looking at the plant for visible signs during flowering that it requires more. Essentially, this period is when the flowers have stopped developing in their height both in terms of overall plant height, and the vertical growth of flowers at each node joining into each other.
Essentially, all vertical growth will have ceased (in terms of both overall plant height and individual flower height) and the flowers will be developing in their width. Essentially it is the time all the small flower sites that have been produced now swell up. At this point of increase in mass, the flowers will likely be demanding more Potassium and Phosphor, so start to dose PK13/14.
This window of time is different for each plant (as each plant will have its own recommended flowering time and speed of which it progresses through certain growth phases) so familiarity with a certain plant type over successive grows will mean you get a better understanding of when the best application time will inevitably be.
3. The pH of the substrate at the time of application.
Mineral nutrients are delivered to a plant in an Ionic form. Ionic is just a fancy word for meaning it is just that element, floating about in the water. Ions are electrically charged, and are either positively charged (called Cations) or negatively charged (called Anions).
When a plant wants either an Anion or a Cation, it has to exchange it – it cannot just take it from the water surrounding the substrate – as an electrical balance must be maintained in the solution.
During the generative period, the ratio of potassium that is taken up increases. Potassium is a Cation, so the root exchanges this element for an Acid (H+) which results in the lowering the pH of the substrate.
The more potassium you are going to add with PK13/14 – the more likely you are to see this effect in your substrate, so it can be wise to check the pH of your substrate before dosing.
For example: Say it comes to dosage time and you are growing hydroponically in Rockwool (with a lower limit of 5.2 as a pH range). You measure the pH of the substrate and it is 5.8. Therefore you know that you have a lot of leeway with the pH to drop after applying PK13/14, so you could assume that a full strength does would be appropriate.
On the other side of the coin, if you come to the application time and you measure that the substrate pH is already at the lower limit of 5.2 – then adding more PK products will potentially push the already low pH down even further and cause lockouts of other nutritional elements. If you measure the pH and it falls halfway between these limits – say 5.5 – then a half-dose of PK13/14 may be wise to consider applying, so to not make a low pH problem worse.
4. Pre-exisiting nutrient deficiency syndromes
PK 13/14 is the most concentrated (and importantly – stable) 1:1 potassium and phosphor based flowering stimulant that can be found on the market. As such, it can sometimes be a bit much for a plant that is not performing at its best, and/or already showing symptoms of deficiencies such as calcium and/or magnesium.
Taking potassium for example, it is directly tied to calcium (and magnesium) and its (their) uptake. Simply looking at each plant cell on a micro level, during their formation in the vegetative and early generative stages, they require a lot of calcium in order to build strong cell walls, that later on are to be loaded up with potassium.
If you see calcium issues before the point of applying PK13/14, you will make this problem worse. A lot of potassium will be taken up, which ends up in the vacuole (water sack) of each cell. This draws more water into the vacuole, like filling it up like a balloon. More potassium means more water draw in and more pressure, but with a weak cell wall it will burst and die leading to wider issues like early ripening and/or Botrytis.
Sometimes, less is more.
In Summary
PK13/14 is a concentrated and powerful nutritional based flowering booster that can directly lead to a larger, denser and more flavorsome harvest. However with great power, comes great responsibility!
Dosing at the correct timing during the right growth phase and at the appropriate rate for how your plant and/or root-zone is performing at the time, can make all the difference in how successful its contribution to your overall yield will be.
Regardless of how deep you want to look into it, following our grow chart is a great foundation for a baseline for success and of course, please try to avoid the temptation of making your own potion by mixing and matching similar nutritional boosters. Keep it simple.
GHEDirect LTD, 
