PK Boost – The Myth Behind When to Apply it

The Truth About PK Boosts: Why Timing and Quality Matter

PK boosts are synonymous with adding bulk to cannabis flower, but their impact can be deceiving and often misunderstood. It’s not just about when to apply a PK boost but understanding the availability and quality of phosphorus (P) & potassium (K) in your base nutrients as well as amendments, and why it’s important. Many growers’ nutrient lines would not think about it at first glance but at least “seem” short on P & K, which limits the plant's potential.  Why do we say this, if they are not short then why would our PK boost make a visible difference in the first two weeks?  Many growers think their plants are good, no issues, but also don’t really know or understand the difference until they actually see the difference.   Many growers also don’t understand the relationship of P & K to photosynthesis and the subsequent functions produced by it. They know what the fertilizer companies and blogs have told them; PK Boost equals bigger flowers but it’s more than that.

We are not going too deep into the weeds, but Photosynthesis is directly related to up to 95% of the biomass of any plant. P & k both are critical for survival but there is research that has been done that tells us the difference between good and better, and better and best is understanding effective amendments.  Proper available phosphorous helps with energy production & transportation, as well as carbon fixation, which is critical for plant sugar production and a host of other interactions. Bottom line if it is not optimal levels, it can slow photosynthetic rates which leads to limiting plant growth. Potassium has a much larger and significant role in photosynthesis, as well as its relationship to secondary metabolites (terpenes, flavonoids, resin, trichomes). Proper available potassium leads to complete photosynthesis cycling, which is the first step in a much larger process to get the highest quality secondary metabolites. Timing and quality of nutrients matter, and for the average grower it’s more a decision of what the grower is looking for out of their grow and how much they believe what the fertilizer companies are telling them.

Fertilizer companies put out feed charts and products that infer that their applications rates are all you need for the best possible plants. How are those application rates creating the best possible flower if every genetic and environment is different? Some strains can handle much more than the minimums, but companies create feed charts to make sure all plants can survive and thrive to a degree. Many of the average growers just want to set it and forget it and hope of great end product but like anything else the more a grower knows the better their grow environment becomes.

We are going to discuss as much about why proper P & K helps the quality of the plant as it is for the flower size. Outside of our PK boost, every other company is selling you a separate PK boost for the bulking of the flower, and ours can too but that’s not what our amendment doses are for, those companies miss an important component, the overall quality of the plant.

So many times, you see growers switching and trying new PK boosts thinking that the product is what makes the difference, and to a certain degree that is true, if the new product you are trying is actually different.  However, many of the products on the market are just different versions of themselves made of the same ingredients with a few added trinkets that were bought from the same suppliers.

Why Base Nutrients May Not Be Enough

Many bloom base nutrients don’t provide enough readily available P and K for medicinal flower. We’ve found that by adding just a small dose of Bloom Accelerant PK boost plants show noticeable improvement in health and quality by weeks 2-3 into flowering. This shows that even though manufacturers’ NPK ratios may seem balanced, they are not enough for the best results. So, when we add a more bioavailable PK, we see a clear difference. Also realize, many base nutrients are from companies selling to all agricultural needs not specifically cannabis based. If a company can sell to a larger audience, they make more money. We get it, capitalism, but that’s doesn’t help our growers.

Education Process

Everyone who started growing plants didn’t know much, and we are all still learning, but there are a lot of growers that have been growing for over 10 years and it’s not a love of the plant but a transactional relationship. There is no issue with that, if we grow this plant, we get flower, and if no one is explaining that P & K have a higher relationship to quality than we knew, then we start to believe in all the “bulk only” marketing and never understand when and why to apply proper, available, P & K.

Many growers use a 1-, 2- or 3-part nutrient line and think they are going to get the highest quality flower, again, companies’ marketing and advertising claims are... subjective. If a grower loves their flower, to them and their friends, maybe it’s considered excellent, it’s all relative.  For those that take the next step, they start to add additional products to the recipe, but this is where the time spent growing to make an acceptable flower is measured against how much time and money, they have want to put in.  There is a large group of growers that are analyzing the least amount of time and energy a grower needs to spend on this transaction to get the acceptable end product. So, the marketing about PK boosts and the blogs and forums telling you how to use them become hopeful sources of good information.

Not All PK Boosts Are Equal

Just because a product says “5-12-26” doesn’t mean the P and K are fully available. Many products, especially salt-based, only have 65% or less of their P & K available to the plant. At GLB, we focus on making PK truly bioavailable (0.03% salts), which is why even small doses of our Bloom Accelerant visually make a big difference within a short amount of time.

The Right Time to Apply PK Boosts

Applying PK boosts based on generalized guidelines or marketing claims can limit your plant’s potential. Each plant has its own needs, and relying on general rules won’t always give the best results. For example, starting a PK boost at week 4 might make it seem like it’s “working,” but if your plant needed those nutrients sooner, you're simply catching up later in the cycle and lost the higher quality potential from early in flower.  Quality can stack but also be lost in a day.

Side Note- Companies make nutrient programs with 10 plus bottles for many reasons, but ultimately for what they believe is their highest quality. The more you can separate out ingredients the best grows can push specific aspects to the nutrient program on a strain dependent basis.  Do not just switch without knowing at least what the bottle says on the label, (not all companies tell you everything to what is actually in the bottle) as you may be thinking you are switching just a PK boost but it may have a lot of other items in it which affects the quality of the plant.

Growers should invest some time and research before substituting a product if not using a company's whole line, unless it has application rates for Individual Amendment Use.  Also, learn if you need to adjust that PK boost you are bringing into the recipe. It may not be the proper amendment or the best for you if you are trying to Frankenstein a program together of a bunch of different products as something might be missing. We see growers like a PK boost from one line and use it with another line and use it at the old application rates.  You may need to make some calculations and that is hard to do with so many variables in each product.  Our PK boost is more available so you cannot take the numbers on the label and assume one product’s bioavailability is the same as another’s.

That's why GLB makes small amendments that work separately without changing a grower's current recipe. It fills in the gaps on growers’ current lines making a better flower. Most products on the market are trying to sell their product as a replacement and not made to put over the top of other companies’ products and recipes.  Ours can as they are clean enough to not over fertilize and compliment a recipe. We will say just this, even though a plant is thriving, if you are going to spend months growing it, and a small tweak can raise your quality, wouldn’t it be worth looking into it?

Why Wait on PK?

Plants need a proper amount of available P and K right from the start of flowering to support photosynthesis and immunity. Without it, they are more vulnerable to pests and diseases. We’ve observed that our Bloom Accelerant 0-17-17, with its highly bioavailable P & K, helps plants grow healthier and more robust at a faster pace. We would recommend additional PK at the latest the start of week 3, to make sure the flowers have a longer, more consistent diet.

The Role of Genetics and Environment

Every plant has a different nutrient uptake pattern based on its genotype and even phenotype. Genetics determine how much a plant can handle, and the environment plays a huge role in whether it can reach closer to its potential. By the way, so newer growers understand, each phenotype can uptake nutrients differently. That is the essence of a phenotype. When growers are pheno hunting, in reality, they are looking for plants within a specific genetic with certain favorable traits or characteristics. All the variances come from how that specific phenotype uptakes nutrients. The better the plant takes up a specific nutrient or micronutrient and can convert those nutrients within the plant, the larger potential for heavier yields or higher secondary metabolites production.

Why do we talk in terms of potential and probabilities?

Growing is a constant, but the growth potential and the actual growth are fluid and very different.  All the positive and negative inputs, environmental or otherwise, within every second of the growing, drying and curing process can ruin a harvest. Very rarely are plants at optimum potential and only for moments, so genetics and nutrients are only potential and can only go as far as the grower's ability to control all their inputs including biotic and abiotic stresses. We will say though, the better the genetics and nutrients, it can make a new grower look seasoned. If a new grower can do even an average grow, our amendments make a significant difference to end product where more experienced growers are surprised by the quality if they don’t use our products themselves. The nutrients a grower uses help remove some limitations, and can at times seem like a cheat code, but one of keys is giving the plant what it needs at the right time, and PK early in flowering helps create a more stable foundation for secondary metabolites. We can only speak about our amendments as we know what the application rates are and what our products do.  If trying to use others they must be tested with trial and error.

The Marketing vs. Reality Gap

Marketing often exaggerates the role of PK boosts in bulking up flowers. The reality is that plants need steady, consistent access to the proper available nutrients throughout their flowering cycle for the highest quality. Waiting to apply additional PK until later can create the illusion of bigger buds faster but applying it from day 1 at less a dose ensures healthier, more gradual growth over time, but that is not how other companies create their products. Best quality is not always the mission statement of every fertilizer company.

Let’s be clear, fertilizer companies do raise their PK amounts in their base nutrients for flower, don’t get us wrong, but is it enough, and how do you know unless you can apply a product that makes a visible difference? In addition, all other PK boosts promise bigger fatter buds, but why is that? If we give an amendment dose of additional PK starting at the beginning of flower, we see larger growth earlier on, but if we use the full PK boost starting week 4-5 of flower, the buds would be smaller earlier but seemingly explode and catch up.  The marketing teams for these companies will say it’s because of their products, which “technically” is true, but what they do not tell you, if you would have gave it the proper amount throughout the whole grow you could get the same size kolas. The difference is the plant has the potential for higher quality as it was getting the ability to use higher levels of photosynthesis and every benefit from that at an earlier state in the flowering process.  

Side Note- What we have found in making bioavailable forms of quality nutrients is that they are prioritized by cells when they are being incorporated into the plant and biological processes. Biology takes the path of least resistance, and salts, though many do not like to hear it, are a stress and it takes additional energy for the plant to deal with it. Our organic chemist has found that certain forms of nutrients including the removal of almost all salts do play a role in biology prioritizing uptake.

Quality Over Quick Fixes

Some companies market “magical” products that promise huge buds, but it’s not about magic—it's about removing nutrient limitations. For example, if a product offers a large dose of PK late in flowering, the plant may seem to explode in size, but it was simply a nutrient deficiency being addressed. Now it’s not really a deficiency, but rather the plant could handle more than it was receiving.  Plants don’t grow “bigger” because of a product, they grow better because they receive what they need.

Why We Recommend Bloom Accelerant As an Amendment

Our Bloom Accelerant is different. With only 0.03% salt, it’s designed to be added to your existing nutrient plan without disrupting it. It helps bridge the gap where your base nutrients might fall short. This doesn’t mean you need to switch everything out, just add what’s missing. We honestly are trying to reduce what goes out nationwide except for our current clients, so we incorporated a version of our Bloom Accelerant 0-17-17 into our BloomSap 0-9-11 product. Please check it out.

The Bottom Line

Depriving your plants of proper P and K early in flowering limits their potential no matter what you are using. Don’t wait until later to see the benefits—your plants need those nutrients from day 1 if possible. Testing our Bloom Accelerant or similar bioavailable PK boosters will help you unlock better quality without relying on marketing claims. If your plants need it, give it to them!

Photos from top down by @Mr._General.G, @WeTheStash_, @NewGen_Hydro, @SweedBeeCo,@Mr._General.G