Guide on Nutrients for Flowering Stage

In this guide, we want to show you not only the essential flowering stage nutrients for larger than life plants. We also want to let you know about some of the “extras” for those looking to go out of this world with their crop this time.

The "Big 3" Nutrients

The most important nutrients you need for your grow are always nitrogen, potassium, and phosphate. The acronym NPK is ubiquitous in growing manuals and fertilizer labels. It stands for nitrogen (N), phosphate (P), and potassium (K). 

Your nutrient product labels may have a set of three numbers: X-Y-Z. That’s your ratio of N to P to K. 

The flowering stage is when adding extra P and K will be crucial. 

Any plant that uses photosynthesis needs nitrogen. A major reason for this is that it needs nitrogen to make chlorophyll. 

It only needs lots of nitrogen during the vegetative stage, however. When your girls start flowering, they need low nitrogen, high phosphorus, and high potassium. 

High phosphorus strengthens roots and increases the number and size of flowers. 

Potassium catalyzes a lot of different functions necessary for flowering. These include carbohydrate metabolism and the absorption of water, nutrients, and CO2. You need lots of it during vegetation, too. 

This makes potassium and phosphorus #’s 1 and 2 in our list of the best flowering stage nutrients. What are the other major players you want on your team to enjoy a bountiful harvest? 

While P and K are the most important nutrients you need during the flowering stage, they are not the only necessary nutrients. The other indispensable nutrients are 3-7 below. 

After that, we’ll look at going above and beyond what nutrients are essential for having any kind of harvest at all. You want the best harvest possible, right? That means lots of giant flowers that are potent and aromatic. 

Essential Micro-nutrients for Flowering Stage


Sulfur is more important during the vegetative stage. It’s essential for making chlorophyll, strengthening roots, supporting water and nutrient uptake, and much more. During this stage, it will create the foundation that makes big buds possible. 

A sulfur deficiency during flowering will kill the flowers. The good news is that sulfur deficiency is rare in soil grows. Even rainwater contains sulfur. Some tap water does as well.


Some cannabis strains may need extra calcium during the flowering stage than what standard fertilizers provide. Doing so may lead to higher bud quality and yield. It’s also very hard for plants to overdose on calcium. It happens, but it’s rare.


One of the most common micro-nutrient deficiencies is boron deficiency. Boron is necessary for sugar transport, bud quality, and bud yield. However, too much of it is toxic and causes root and leaf burn. 

The flowering stage requires more boron. 

According to a study at North Carolina State University, the optimal fertilization rate is somewhere between 8.75 and 10 parts per million. As of June 24th, 2020, they are still trying to pinpoint the exact range. 

Top sources of boron for growers are borax and boric acid.


You need more magnesium during flowering. Add some extra if you want big flowers and healthy natural aromas. 

Magnesium deficiency stunts growth during vegetation and flowering. If you see yellow or brown spots on the lower leaves, and it climbs upward, you may be low on it. 

Plants growing in a coco medium may have a hard time absorbing magnesium. In hydro, they won’t absorb it if the pH is below 5.0. If you overwater your soil grow, you may lock out magnesium. 

Magnum by Humboldt County’s Own contains the flowering nutrients magnesium, sulfur, and vitamin B1.

Learn More About Magnum by Humboldt County’s Own


Manganese helps nitrates create the proteins necessary for a great harvest. It also helps produce chlorophyll and protects roots from diseases. When deficient, your plants won’t grow. 

It can also be toxic to your plants in high amounts, just like boron. 

One cause of deficiency is a pH higher than 6.5 in the growing medium. 5.5 and below can cause an overdose of manganese. Another is use of all-purpose fertilizers that don’t have enough trace nutrients.

Other Key Nutrients & Ingredients for Blooming Plants

L-Form Amino Acids

These are natural chelators that boost nutrient absorption and make metabolism more efficient. This means less nutrients are needed for your grow. They also improve bud color and size and accelerate photosynthesis. They work well for any growing medium. 

Two amino acids popular with growers are L-Glycine and L-Glutamic Acid.

Learn About NPK’s RAW Amino Acids

If you need a translation, L-form amino acids give you bigger and better buds.


This is a growth-stimulating hormone that is perfect for early flowering. It will increase your bud size. 

There are some bloom booster fertilizers that contain it. Two natural sources are alfalfa and kelp. You can make a “tea” with alfalfa meal or kelp and use it as a foliar spray. There is no shortage of instructions on the internet.

Humic Acid

Humic acid improves soil quality, nutrient absorption, and water retention during all growing stages. It bonds with nutrients in a way that makes them easier to absorb.

Learn About NPK’s RAW Humic Acid Supplement

Bio-Osmotic Potentiators

Say bio-osmotic potentiators out loud. It’s actually fun. These compounds boost terpenoids, which give your buds higher quality flavors and aromas. 

One product that supplies bio-osmotic potentiators is called Terpenator.

Learn More About Terpenator by Rhizoflora

Citric Acid or Vitamin C

You can use ascorbic acid or citric acid when your plants are stressed during any growing stage. Either one will stimulate antioxidant activity and improve growth and immunity. 

You can find both in herb and vitamin shops both online and offline. They usually come in powder form.

Fulvic Acid

Fulvic acid goes well with humic acid. It works well as a foliar spray. Both of these acids will decrease the amounts of nutrients your plants need and help you create the harvest of your wildest and most erotic cannabis dreams. 

In a study by AgTonik LLC and PSI Labs , researchers found that adding a fulvic acid supplement to a hydroponic grow increased yield by 21% compared to a control without reducing potency. 

Learn About Ful-Potential Fulvic & Humic Acid Supplement by X Nutrients

Vitamin B1

Vitamin B1 increases flower size, protects against sunburn, reduces stress, and boosts production of all the good cannabinoids. Use it during flowering or other stages. To protect against sun damage, make a foliar spray with it.


Yes, sugar makes your buds bigger. It is the fuel that makes flowers possible to begin with. Halfway through flowering is when your buds start fattening, especially if you’re using the nutrients mentioned above. This is the perfect time to add carbs. 

Growers love fattening their buds with molasses. 

Ask a Growing Expert About Flowering Stage Nutrients

We’re not only retailers. We’re growers! Call or text us with any questions about your grow.
Grow Supply Shop 
9am-5pm EST, Monday through Friday
GuideHow to grow bigger

Leave a comment

All comments are moderated before being published

Top Sellers

Humboldt County's Own Sonic Bloom W/VitsHumboldt County's Own Sonic Bloom W/Vits
Sale priceFrom $25.99
Humboldt County's Own Sonic Bloom W/Vits
In stock, 18 units
20W Monkey Fan Oscillating v2.020W Monkey Fan Oscillating v2.0
Sale price$53.10 Regular price$59.00
20W Monkey Fan Oscillating v2.0
Sold out
Humboldt County's Own Starter Pack/ Complete Soil Nutrient KitHumboldt County Starter Park Everything You need in one box
Sale price$114.99 Regular price$149.99
Humboldt County's Own Starter Pack
In stock, 19 units