Critical Perspectives on Bloom Boosters for Flowering

By Kent Gruetzmacher
Published: May 9, 2018 | Last updated: June 13, 2022 11:07:17
Key Takeaways

For the most part, nutrient companies create and market their brands for the novice cultivator—paying particular attention to ease of use in small-scale home gardens. While these all-inclusive fertilizer lines are invaluable for hobbyists, more advanced horticulturists have the knowledge and experience to achieve results without the use of bloom boosters.

One of the most popular trends in the modern gardening marketplace is that of the bloom booster. Sold under catchy names and colorful packaging, nutrient companies market bloom boosters as essential fertilizers to be used during the flowering phases of plant growth, including them on the feeding schedules sold with their products. Bloom boosters can add a significant expense to garden operations, so it’s best to understand them and maximize their potential.


We reached out to accomplished cultivator and fertilizer developer Aaron Hoare to learn more about bloom boosters. Hoare, like most expert gardeners, emphasizes critical analyses in his horticulture practices, paying particular attention to plant physiology and the creation of nutrient feeding programs founded on basic plant needs.

To gain a better understanding of fertilization methodology in relation to flowering phases and bloom boosters, Hoare has provided a basic overview of the practices he uses in the development of his own nutrient mixes. These procedures are structured around both irrigation and runoff water analytics.


N-P-K Ratios, Water Analysis, and Parts Per Million

While the utility of fertilization schedules included with most modern nutrient lines is unquestionable for novice growers, these same gardeners will likely have to learn the basic elemental analyses of fertilizers if they hope to achieve extraordinary harvests. This brings us to the N-P-K ratio featured on all fertilizer products: nitrogen (N), phosphorus (P), and potassium (K).

These three elements are known as macronutrients and they serve as the essential foods for all plant life. Moreover, different levels of these macronutrients are required for stimulating growth during different phases of a plant’s life. During the flowering phase, many horticulturists agree that vigorous flower growth requires higher levels of phosphorus and potassium combined with lower levels of nitrogen. As a result, bloom boosters generally present an N-P-K ratio somewhere in the neighborhood of 0-50-30 or 0-39-25.

According to Hoare, cultivators looking to explore their nutrient feeding regiments, including the use of bloom boosters, should begin by testing their irrigation and runoff water with a laboratory. These lab readings will show the parts per million (ppm) of each macronutrient in their water after nutrients are mixed, as well as those built up in their soil. The results provide a logical point of departure in deciding whether or not to use bloom boosters or make any other necessary tweaks to a feeding schedule.


Hoare applies this analytical, data-driven approach for fertilizer development in his own nutrient formulas. From these studies, he came to the conclusion that with flower phase macronutrients, the ideal “ready for plant” irrigation water analysis in parts per million should be 125 ppm nitrogen, 60 ppm phosphorus, and 165 ppm potassium. It should be noted, again, that Hoare’s figures are formulated via a holistic approach to fertilization scheduling—that takes into account variables like nutrient buildup in soil.

While most gardeners, novices and experts included, don’t have the time to consistently test their irrigation and runoff water with a laboratory to get ppm readings, this is a great way for one to understand exactly what their plants are being fed. Testing both irrigation and runoff water two to three times during a plant’s life will provide enough information to restructure a fertilization program founded on the basics.


For Hoare, he says it is a better bet to base nutrient formulations on the ppm readings of macronutrients in irrigation and runoff water rather than what is recommended on a nutrient feeding schedule. With this critical approach, Hoare recommends a N-P-K ratio of 7-6-12 during the flowering period. Obviously, these numbers stand in stark contradiction to the 0-50-30 ratios that abound in bloom booster formulations.

What Does It All Mean?

Plants can only handle a limited amount of fertilization of any macronutrient before the process becomes counterproductive. This notion is where Hoare’s ppm data really comes into play concerning bloom boosters. Because, according to Hoare, an overabundance of any macronutrient in irrigation water or a growth medium will actual hinder the uptake of all macronutrients. As far as bloom boosters are concerned, a majority of standard nutrient feeding regimens already contain sufficient phosphorus and potassium to stimulate flower growth. Moreover, most expert growers agree that too much phosphorus and potassium can be toxic for plants and can actually retard flower growth.

If one wants to follow the more simplistic feeding approaches of Hoare and his contemporaries, they shouldn’t apply bloom boosters if their flowering nutrients already contain 40-60 ppm of phosphorus and 150-170 ppm of potassium when mixed with water. Again, these numbers are based on a holistic approach to fertilization—taking into account factors like nutrient buildup from months of feeding.

Evolutions in modern gardening are sometimes stimulated by contradictions in thought and practice, like those seen in the delineations in theory presented by nutrient lines and bare bones approaches like Hoare’s. Concerning bloom busters, this difference in methodology could simply boil down to the experience levels of cultivators.

For the novice gardener who doesn’t have the time, or interest, to test fertilizer formulations for maximum output, brand nutrient feeding schedules are an extremely practical choice. There is no doubt that they have given beginners the ability to produce crops unthinkable 20 years ago. If bloom boosters help these beginners achieve relatively good harvests, they can obviously benefit from them. For more advanced, scientifically minded horticulturists, bloom boosters may not be as necessary.


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Written by Kent Gruetzmacher | Writer, Owner of KCG Content

Profile Picture of Kent Gruetzmacher

Kent Gruetzmacher MFA is a Colorado-based writer and owner of the writing and marketing firm KCG Content. Kent has been working in the cannabis and hydroponics space for over a decade. Beginning in California in 2009, he has held positions in cultivation, operations, marketing, and business development. Looking specifically to writing, Kent has worked with many of the leading publications and marketing agencies in the cannabis space. His writing has been recognized by such icons as Steve D’Angelo and Rick Simpson.

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