Advanced Nutrients HammerHead - Zero-Nitrogen PK Bloom Booster
Best for: Growers in mid-to-late flower who want a dedicated potassium-phosphorus push for denser, heavier flowers.
Our thoughts
Zero nitrogen is the whole point of a proper PK booster, and HammerHead sticks to that brief - no wasted nitrogen encouraging leafy growth when you want plants putting everything into flower development. It's a bolt-on additive, not a base nutrient, so it works alongside whatever base feed you're already running.
HammerHead is a dedicated PK (phosphorus-potassium) bloom booster from Advanced Nutrients, carrying an NPK formula of 0-4-12 for a roughly 1:3 phosphorus-to-potassium ratio. The zero-nitrogen formula is deliberate - by week 2 of flower, plants don't need more nitrogen pushing leaf growth, they need phosphorus and potassium to support flower and resin development. HammerHead uses potassium citrate technology, which is designed to improve nutrient uptake efficiency while reducing the salt build-up risk that comes with heavier PK feeding.
It's specifically formulated to work with Advanced Nutrients' Sensi Terra series for soil growers, but it's also fully compatible with all Advanced Nutrients pH Perfect and non-pH Perfect base nutrients, and with base nutrients from other brands too - so it's a flexible add-on regardless of what you're already feeding.
How it compares
PK boosters are a crowded but well-established category, and HammerHead is one of the more heavily potassium-weighted options in it.
- Vs House & Garden Bud-XL: both are established PK boosters; Bud-XL leans on a slightly different mineral balance, while HammerHead's 1:3 PK ratio is specifically weighted toward potassium.
- Vs Canna PK 13/14: Canna's PK booster is a long-standing category staple with a heavier overall PK concentration; HammerHead's potassium citrate approach is aimed at reducing salt build-up over a feeding cycle.
- Vs Growth Technology NPK Boost: a more budget-focused option; HammerHead sits at a higher price point in exchange for Advanced Nutrients' branded formulation and compatibility claims across systems.
If you're already running an Advanced Nutrients base, HammerHead is the natural PK add-on; if not, it still slots into most other base nutrient programmes without issue.
Usage guidance
HammerHead is designed to be added during a specific flowering window rather than used throughout the whole cycle.
Dosage
Add 2ml of HammerHead per litre of nutrient solution, used from around week 2 through to week 7 of the flowering phase.
Mixing
Add to your reservoir alongside your base nutrient and any other bloom-phase additives, mixing thoroughly before use.
Stopping point
Ease off PK boosters like HammerHead in the final week or two before harvest, moving toward a flush or finishing product instead.
Soil growers
If you're running Advanced Nutrients' Sensi Terra series, HammerHead is formulated specifically to complement that soil-based base nutrient.
Technical specifications
- Product type: PK (phosphorus-potassium) bloom booster
- NPK ratio: 0-4-12
- PK ratio: Approximately 1:3
- Key technology: Potassium citrate for improved uptake, reduced salt build-up
- Growth phase: Flowering (weeks 2-7 typically)
- Recommended dosage: 2ml per litre
- Compatibility: All Advanced Nutrients base lines (pH Perfect and non-pH Perfect), formulated to complement Sensi Terra, and compatible with other brands' base nutrients
- Sizes available: 250ml, 500ml, 1L, 5L
- Brand: Advanced Nutrients
Who this is for
- Growers in flower who want a dedicated PK push without adding unwanted nitrogen
- Sensi Terra soil growers looking for the matched bloom booster in the same system
- Growers on any brand's base nutrient wanting an established PK additive that layers in cleanly
- Anyone chasing denser bud structure and heavier finished weight in flower
Best used as part of a wider flowering feed programme rather than on its own.
Our take
HammerHead does exactly what a PK booster should - zero nitrogen, a clear potassium-weighted ratio, and a genuine mechanism (potassium citrate) behind the salt build-up claims rather than vague marketing language.
Does exactly what it should, day in, day out, for growers who already know PK boosters work and just want a reliable one from a brand they trust.
