Key takeaways
- Mammoth P is a bacterial inoculant, not a fertilizer: four bacteria free up phosphorus and micronutrients that are already in your root zone.
- The current label rate is 0.6 mL per gallon (0.16 mL per liter), applied twice a week in soil, coco or hydro.
- In a 2017 coco and perlite trial on a medicinal flower crop, treated plants yielded 16.5% more bud: 295.7 g vs 253.9 g per light.
- It contains no mycorrhizae, keeps more than two years unopened, and should be used within six months of opening.
- Mammoth P left shelves in 2024 and came back with an updated formula; it is in stock at GrowersHouse today.
After a year-long hiatus, Mammoth P is back—and at a lower price than before. This microbial inoculant has long been trusted by both commercial growers and hobbyists to unlock more yield, better terpene profiles, and healthier root systems. Backed by peer-reviewed studies, Mammoth P makes phosphorus—the backbone nutrient for plant energy and flowering—more available than ever.
Skip the blog and check out these leading GrowersHouse.com Mammoth products: Mammoth P Active Microbials and Mammoth Control.
If you’re wondering whether Mammoth P is right for your grow, this guide answers the top questions we get from customers at GrowersHouse and breaks down why this product continues to stand out.
[Short on time? Here’s a TLDR summary - Mammoth P is back—now at a lower price—bringing growers one of the most effective phosphorus-mobilizing microbial products on the market. Backed by university studies, Mammoth P uses a consortium of beneficial bacteria (including Enterobacter cloacae) to unlock bound phosphorus and micronutrients in your soil, improving nutrient uptake, plant health, and yields. Whether you’re running soil, coco, or hydro, Mammoth P makes phosphorus more available exactly when your plants need it most, especially during flowering. The result? Bigger buds, better flavors, and higher returns—all with less wasted fertilizer.]
What is Mammoth P used for?
Mammoth P is a microbial biostimulant aimed at mobilizing phosphorus (P) in your growing medium. It features a consortium of beneficial bacteria (including Enterobacter cloacae) that release trapped phosphorus and micronutrients, increasing their availability for plant uptake.
Growers use Mammoth P to:
- Increase bud yield and flower density
- Improve phosphorus uptake efficiency
- Enhance flavor and terpene production
- Support stronger root development and plant vigor
Controlled “medicinal herbs” trials revealed that Mammoth P significantly boosted bud yield compared to untreated controls. (Read here—the 2017 bud yield study, PDF.)
Mammoth P feed chart: how much and how often
The current label rate is simple, and it is the same for every medium and every stage. Mix 0.6 mL per gallon of water or nutrient solution and apply it twice a week. Shake the bottle well before each use.
| Item | Mammoth P |
|---|---|
| Rate (US) | 0.6 mL per gallon |
| Rate (metric) | 0.16 mL per liter |
| How often | Twice a week, in soil, coco, soilless or hydro |
| Before use | Shake the bottle well |
| 1 gallon container | Treats up to 6,308 gallons (label) |
| 5 gallon container | Treats up to 31,450 gallons (label) |
| After opening | Use within 6 months |
The 2017 trial in the science section below followed the label of that time, 0.6 to 4 mL per gallon with every watering. The current, updated formula runs at the lower 0.6 mL rate twice a week, so older feed charts you find online will not match the bottle in your hand.
Did Mammoth P go out of business?
No. Mammoth P went missing from many hydroponic store shelves in 2024, which is where the rumor started. It has since returned with an updated formula, and the current label names Mammoth Ag, Inc. as the maker of the patented product. GrowersHouse carries it again in 250 mL, 500 mL, 1 liter, 1 gallon and 5 gallon sizes.
Is Mammoth P worth it?
Absolutely—because it enables you to maximize the phosphorus you’re already investing in.
Phosphorus fertilizers can be inefficient, with a large portion of the P becoming locked in soil or media.
The microbes in Mammoth P function as biological unlockers, solubilizing bound phosphorus so your plants can utilize it instead of letting it go to waste.
A study across various crop types demonstrated consistent growth promotion, increased biomass, and enhanced nutrient use efficiency when Mammoth P was applied (Read here— the 2016 crop study, PDF). That study, published in PeerJ, tested wheat, turf grass, jalapeño, cherry tomato and basil.
The return on investment stems from both improved yields and decreased fertilizer waste.
What’s in Mammoth P?
Mammoth P contains a proprietary microbial consortium chosen for its ability to mobilize phosphorus.
Key organisms include:
- Enterobacter cloacae
- Citrobacter freundii
- Comamonas testosteroni
- Pseudomonas putida
These microbes produce enzymes that unlock bound phosphorus and micronutrients. Think of them as “beneficial bacteria teammates” collaborating with your root zone to ensure nutrients keep flowing.
Mammoth P ingredients and CFU count
| Organism | Concentration |
|---|---|
| Enterobacter cloacae | 1 x 10⁶ CFU/mL |
| Citrobacter freundii | 1 x 10⁶ CFU/mL |
| Comamonas testosteroni | 1 x 10⁴ CFU/mL |
| Pseudomonas putida | 1 x 10⁴ CFU/mL |
| Total | 2.02 x 10⁶ CFU/mL |
Does Mammoth P contain mycorrhizae? No. The label lists these four bacteria and no mycorrhizal fungi. The product panel also describes a clean-running, near-neutral pH formula.
Mammoth P vs Tribus
Growers often compare Mammoth P with Tribus Original from Impello Biosciences. Tribus Original is discontinued at GrowersHouse. The two take different approaches, as the table shows.
| Label detail | Mammoth P | Tribus Original (discontinued) |
|---|---|---|
| Organisms | Enterobacter cloacae, Citrobacter freundii, Comamonas testosteroni, Pseudomonas putida | Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus pumilus |
| Concentration | 2.02 x 10⁶ CFU/mL | 1 x 10¹⁰ CFU/mL |
| Rate | 0.6 mL per gallon, twice a week | 1 mL per gallon, once a week or as often as every watering |
A higher CFU count does not make one product better than the other. The organisms are different, and Mammoth P's consortium was selected and tested specifically for phosphorus mobilization.
What does the “P” stand for on a fertilizer label?
The “P” in N-P-K fertilizer labels stands for phosphorus (P₂O₅ equivalent).
Because the label figure is phosphate, not pure phosphorus, the real phosphorus content is lower than the number suggests. P₂O₅ is about 44% phosphorus by weight, so a nutrient labeled 0-10-0 carries roughly 4.4% elemental phosphorus.
Phosphorus plays a crucial role in:
- Energy transfer (ATP)
- Root growth and development
- Flower initiation and seed formation
- Without sufficient phosphorus, plants can struggle—yield and quality both decline.
Does Mammoth P go bad?
Mammoth P is a living product, so proper storage is important. Unopened containers kept in a cool, dry environment remain viable for well over a year.
Once opened, keep sealed and avoid extreme temperatures. The microbes are hardy and shelf-stable under standard grower conditions, but always verify expiration guidance on the label.
The manufacturer rates the shelf life of an unopened container at more than two years and recommends using it within six months of opening. Store it out of direct sunlight and away from hot and cold extremes.
What does phosphorus do for plants?
Phosphorus is vital for plant metabolism. It aids in converting sunlight into usable energy, supports root expansion, stimulates bud initiation, and impacts the overall quality of the harvest.
Phosphorus deficiency may manifest as:
- Stunted growth
- Purpling of stems or leaves
- Weak root development
- Poor bud set
By increasing phosphorus availability, Mammoth P helps your plants get what they need to achieve their full genetic potential.
Breaking Down the Science: Mammoth P and Medicinal Flower Yield
A 2017 peer-reviewed study tested Mammoth P on a medicinal flower crop grown in coco/perlite under typical indoor cultivation conditions. The researchers compared plants treated with Mammoth P to a control group that received the same nutrients but without Mammoth P.
Key Findings:
- Yield Boost: Plants treated with Mammoth P produced 16.5% more bud yield than untreated plants (295.7 g vs 253.9 g per light on average).
- Stronger Plants: Treated plants were taller (+4.1 cm) and had thicker stems (+13.5% basal diameter)
- Integration: Mammoth P worked seamlessly with existing hydro/soil-less nutrient regimens—no need to change standard practices.
- Why It Matters: For indoor growers, where every gram of bud counts against high operating costs, a 16.5% increase in yield can significantly boost net income while reducing risk. Mammoth P helps plants grow stronger and more productive without requiring a change in your grow system. Read the full study here
One thing to know before you quote the number: both studies were written by researchers at Growcentia, the company that developed Mammoth P, working with Colorado State University. They are published and peer reviewed, but they are not independent of the manufacturer.
Final Take: Why Growers Trust Mammoth P
Backed by Science – Published medicinal herbs and crop studies confirm higher yields and enhanced phosphorus uptake.
Powered by Microbes – A specialized bacterial consortium aimed at nutrient mobilization.
Versatile – Effective in soil, coco, and hydro systems.
Now Lower Priced – Relaunched at a lower price than before.
If you’re looking to boost yield and quality without overloading your grow with extra fertilizer, Mammoth P is the proven microbial solution.