Best Bloom Boosters for Cannabis: 10 Grower-Rated Picks

The best bloom booster for cannabis is one that matches your base nutrients and growing medium: a phosphorus and potassium (PK) additive for hydro and coco, or a gentler organic bloom enhancer for living soil. Below are 10 bloom boosters growers rate highly, with label NPK, dose and what each one is built for, plus how to use them without burning your plants.

A bloom booster (also sold as a bloom enhancer, flower booster or bud booster) is an additive you feed during the flowering stage on top of your base nutrients. Most add extra phosphorus and potassium, the two elements cannabis uses most while it builds buds. Many also carry amino acids, carbohydrates, humic acid or plant hormones that the makers say help flower size, density and aroma. If you’re still choosing a base program, start with our guide to fertilizer for the flowering stage.

Bloom booster comparison at a glance

NPK figures are as listed by each manufacturer at the time of writing. Labels change, so check the bottle before you mix.

How to choose a bloom booster

• Match your medium. In coco and hydro, roots take up nutrients fast, so a concentrated PK booster works well at a low dose. In living or amended soil, an organic bloom enhancer is less likely to upset the soil biology.
• Check what your base already gives. Many bloom base nutrients already carry plenty of P and K. Stacking a high PK booster on top can cause nutrient burn or lock out calcium and magnesium.
• Look at timing. Most PK boosters are meant for a few weeks in mid-flower, not the whole cycle. Organic stimulants are usually gentler and can run longer.
• Watch your EC. A booster raises the strength of your solution. Some feed charts already account for it, and others expect you to lower the base feed a little.

Want the basics behind those letters? Read what N-P-K means. We also compare three of these products side by side in Rock Resinator vs Big Bud vs Massive Bloom Formulation.

Our 10 grower-rated bloom boosters

1. Massive Bloom Formulation by Green Planet Nutrients

NPK:1-1.5.2.8.

Dose: 20 mL (4 tsp) per 4 L (1 gallon)

This bloom enhancer is amazing as it contains many nutrients other bloom enhancers simply lack. With L-form amino acids, a specially formulated vitamin profile, triacontanol (a sugar based alcohol found in bee waste and alfalfa which acts as a natural plant steroid), enzyme activators, a unique blend of carbohydrates, low molecular weight humic acid, a chelated mineral profile, and the essential nutrients phosphorus and potassium, this bloom formulation is completely loaded to ensure your plants grow healthy and strong with big, beautiful flowers. It increases and promotes flower size, aromatics, essential oils, chlorophyll content, photosynthesis, CO2 utilisation, proper NPK ratios, cell expansion and content, cell wall thickness, floral components, and resistance to stressors. Also, one of the most valuable aspects of this great formula is that growers have reported up to and beyond a 30% increase in dry weight. That’s amazing!

Massive Bloom Formulation is the premier flowering additive and enhancer and is suitable for use with any nutrient regime, no matter the technique or grow medium. Massive Bloom Formulation is designed to be used from week 3 throughout the duration of the flowering cycle, stopping the last week for the flushing period. The recommended use is 20 mL per gallon of nutrient solution. As it increases your ppm to 400 ppm, you may need to cut back a little on your nutrient system. However, the feed schedule offered by Green Planet Wholesale takes into account the extra ppm, so it is not necessary to cut back on your nutrients strength using Green Planet Nutrients, unless your particular plant variety prefers a lower nutrient strength.

2. Terpinator by Rhizoflora, Inc

NPK: 0-0-4
Dose: start in veg with 5-10 mL (1-2 tsp) per 4 L (1 gallon), then increase to 10-30 mL (2 tsp-2 tbsp) to per 4 L (1 gallon) during bloom.

Terpinator by Rhizoflora is also distributed by Green Planet Wholesale in Canada and there is nothing else quite like it on the market. Terpinator was formulated from years of researching naturally occurring plant compounds that are bio-osmotic potentiators. Through this patented scientific process, your plants use these compounds to enhance their production of terpenoids and plant oil producing glands. These glands are brought to their maximum potential and size using Terpinator along with any nutrient program for “frostier” and more potent buds.

Some types of plant oils contain terpenoids, which are compounds that contain special odour molecules that consist of repeating units of a 5-carbon structure called isoprene. These odour compounds have been proven to affect us in many ways, such as through aromatherapy. Terpinator also catalyzes steps in a plant’s normal metabolism that will protect and prolong fragrances of your plant’s dried fruits and flowers.

3. King Kola Powerful Bloom Booster: By Emerald Harvest

NPK: 0.3-2-3 

Dose: 12 mL (2 1/2 tsp) per 4L (1 gallon)

Apart from its awesomely illustrated product label, King Kola by Emerald Harvest is a powerful bloom booster designed to produce bigger, heavier blossoms. High in potassium and phosphorus and fortified with nitrogen derived from hemp, it encourages prolific flowering and massive, weighty blooms by powering up your plant’s productivity.

Another key ingredient essential to King Kola’s powerful bud builder are L-form amino acids, which act as natural chelators so your plants can soak up a full amount of nutrients, which results in a great yield. L-form amino acids encourage plant metabolisms to work efficiently, so there’s little waste of the valuable nutrients your plants need.

4. Awesome Blossoms by Technaflora

NPK: 2-11-11

Dose: 5mL (1tsp) per 4L (1 gallon)

Technaflora Awesome Blossoms is designed for all flowering plants and is a scientifically blended flower stimulant which promotes prolific blooms at multiple budding sites. A solution of super phosphates, it is formulated with micro and macro elements which stimulate dense and strong flowering. Containing ammonium nitrate, mono potassium phosphate, diphosphoric acid, boric acid, copper sulfate, iron dtpa, iron edta, manganese sulfate, sodium molybdate and zinc sulfate, it provides your plants the essential vitamins and minerals to grow the biggest and fullest blossoms.

This exceptional plant nutrient can be used at regular intervals throughout the flowering stage and facilitates a crowning effect in which new blossoms emerge from within existing flowers. It also enhances essential oil production, maximizing overall crop weight and amplifies aroma and flavour.

5. Bloombastic by Atami

NPK: 0-14-15 w/w, 0-20-21 w/v

Dose: 2 mL (½ tsp) per 4L (1 gallon)

Atami Bloombastic is packed full of bio-stimulators and bio-minerals suitable for the last flowering and ripening phase of plant growing. It is a booster, accelerator, top hardener, quality improver and an essential oils increasing product containing organic based materials such as sea kelp and clay minerals. Bloombastic is designed for all flowering plants, can be used on all substrates, as well as used in hydroponic growing methods, geoponic growing methods and aeroponic growing methods. It also provides your plants the essential vitamins and minerals with the adequate PK spike in the final phase to grow the biggest and fullest blossoms when directions are followed correctly.

Bloombastic is compatible with any base nutrient and can be used at regular intervals throughout the flowering stage, increasing the dose from 2 mL per gallon to 4 mL per gallon during the last week of blooming, which results in dramatic effects when the metabolic enhancers kick in, ensuring big, beautiful and dense buds.

6. Kool Liquid Bloom by General Hydroponics

NPK: 0-10-10

Dose: 5-10mL (1-2 tsp) per 4L (1 gallon)

General Hydroponics Liquid KoolBloom is a highly concentrated nutrient additive and promotes vigorous flowering and helps with ripening in annual flowers and herbs. Liquid KoolBloom is rich in phosphorus and potassium and fortified with a secret blend of ingredients.

Liquid KoolBloom enhances essential oil and fragrance production by mildly stressing plants during the blooming stage. It can also be used as a nutrient additive during the second phase of reproductive growth and as a stand-alone nutrient at the end of a plant’s life cycle.

Formulated to boost potency and enhance the performance of all types of nutrients, General Hydroponics Liquid KoolBloom promotes healthier, larger, and heavier fruits and flowers.

7. Hydroplex by Botanicare

NPK: 0-10-6

Dose: 2-3 mL (½-1 tsp) per 4L (1 gallon) of water.

Hydroplex Bloom Maximizer contains a broad range of amino acids, additional trace minerals, and selected beneficial vitamins. Hydroplex surpasses the standard of PK boosters by increasing your plant’s resistance to external stresses and amplifies enzymes, chlorophyll, essential oil and sugar production.

Hydroplex benefits your plant by increasing your bloom initiation and growth, essential oil, natural sugar, chlorophyll and protein production, increases fruit density and quality, flower size, development of enzymes and vitamins, boosts resistance to external stresses, and is safe to use with any nutrient program.

8. Bio-Heaven by BioBizz

NPK: 0.91-0.18-0.24

Dose: start with 2 mL (½ tsp) per 4 L (1 gallon), then increase to 5 mL (1 tsp) per 4 L (1 gallon)

Bio-Heaven improves the effects of sprays and fertilisers used as plant feed. Bio-Heaven also rids the plant of toxins, repairs chlorophyll production and stimulates the plant. Made from all organic material, Bio-Heaven is heavily rich in carefully selected bio-enhancers and amino acids, but low in NPK. The reason this product is lower in NPK is because it contains stimulants that enhance nutrient uptake of your plant so a fast and complete absorption of important nutrients occurs. It also increases the chelate of essential macro and micronutrients, allows the plant to hold onto humidity, stimulates enzymatic activity, outstanding source of carbonic acid for the micro-organisms in your soil and it improves overall quality and quantity of your yield

Bio-Heaven may be used during the entire grow and flowering stages of your plants and is compatible with every substrate, on coco and in hydroponic systems.

9. General Organics BioBud: By Hydrofarm

NPK: 0-0-1

Dose: 2.5-5 mL (½ – 1 tsp) per 4L (1 gallon)

BioBud by Hydrofarm is a bloom stimulator that provides your flowering plants with essential minerals and amino acids to encourage big, abundant flowering and fruit production.

Used during the flowering phase of plant growth, alongside any base fertilizer or nutrient program, BioBud increases your plant’s metabolic activity and uptake of minerals by using bio-stimulants and organic transport enhancers, which induce abundant and dense floral clusters during flowering and fruiting phases. Biobud is compatible with any garden soil, potting mix, hydroponics or other growing mediums.

10. Big Bud by Advanced Nutrients

NPK: 0-1-3

Dose: 6 mL (approx 1 tsp) per 4L (1 gallon) during weeks 2-4

Big Bud is one of the best bloom booster products specifically designed for marijuana growers in mind. Most bloom boosters contain double the amount of the wrong types of P and K, which is not incredibly useful for your plants and is also a huge waste of resources in the long run. Big Bud contains the correct amount phosphorus and potassium for your plants that is very easy to absorb, so there is minimal waste of P and K.

Big Bud also contains citric acid and other substances, which aid in supplementing cellular respiration and help your plants transfer nutrients and energy from their roots to their leaves. Ascorbic acids, another important acid for your plant, help your plants photosynthesize.

This great product contains 20 different L-form amino acid. L-Cysteine provides your plant with sulfur, and along with L-Glycine, is a prime element of the formation of an internal plant protectant compound called glutathione. By boosting these nutrients for your plants, you are able to maximize your yield up to 20% with Big Bud.

How to use a bloom booster without burning your plants

1. Start at half the label dose for the first feed and watch the leaf tips for a few days.
2. Add the booster to your nutrient solution last, after the base nutrients, then check and adjust pH.
3. Measure EC or PPM after mixing. If it’s well above your usual feed, lower the base nutrients slightly.
4. Stop the booster when the label says to, usually in the final week or two before harvest.
5. If leaf tips start to brown, cut back. Our nutrient burn guide covers what to do next.

A booster won’t fix a deficiency caused by bad pH. If your lower leaves have yellow, crispy edges in flower, check for potassium deficiency and your runoff pH before adding more product.

Frequently asked questions about bloom boosters

What is the best bloom booster for cannabis?

There isn’t one best bottle for every grow. Growers who want a complete bloom enhancer often pick something like Massive Bloom Formulation, while hydro and coco growers who already run a strong base program tend to prefer a straight PK booster used for a few weeks in mid-flower.

What is the best bloom booster for coco?

Coco takes a liquid PK booster well, because the roots get nutrients quickly. Keep the dose low, feed to a little runoff every time, and watch your EC so salts don’t build up in the coco. Calcium and magnesium levels matter more in coco, so don’t let a high PK product crowd them out.

What is the best organic bloom booster?

For organic grows, look for products built on natural sources and bio-stimulants, such as Bio-Heaven or BioBud on this list, or top dressing with bat guano or kelp. They work more slowly than mineral PK boosters but are easier on soil biology.

When should I start using a bloom booster?

Most PK boosters go in from about week three of flower, once buds have set, and stop a week or two before harvest. Some organic stimulants can start earlier. Follow the label for the product you use, because timing varies a lot between brands.

Is a PK booster the same as a bloom booster?

A PK booster is one type of bloom booster. It mainly supplies phosphorus and potassium. Other bloom boosters add amino acids, carbohydrates or hormones on top of PK, and some organic enhancers barely add any NPK at all.

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