Aptus Super-pk - High-Strength Organo-Mineral PK Bloom Stimulator
Best for: Growers wanting a concentrated phosphorus-and-potassium push through the flowering stage to support bud development.
Our thoughts
This is Aptus's answer to the classic PK booster, and the numbers back it up: 20% phosphorus and 23% potassium is a genuinely strong concentration, so a little goes a long way. It's the kind of additive that makes a visible difference to bud development when it's used at the right point in flowering, not before.
Aptus Super-PK is an organo-mineral bloom stimulator combining a high concentration of phosphorus (20%) and potassium (23%) with L-amino acids that help the plant put those minerals to use efficiently. Phosphorus and potassium are the two elements most closely tied to flower and bud development, and Super-PK is designed to supply both together at a strength well above what most base nutrients provide on their own.
Because of its strength, Super-PK is intended for use once flowering is properly underway rather than earlier in the grow, and Aptus recommend holding off with more sensitive plants until later in the bloom phase to avoid overloading young flower sites before they're ready for it.
How it compares
PK boosters are one of the most competitive additive categories in flowering nutrition.
- Versus Canna's PK 13/14: PK 13/14 is a long-standing, well-known PK booster at a lower concentration than Super-PK's 20-23% figures, meaning Super-PK is dosed in smaller volumes for a comparable effect.
- Versus House & Garden's Bud-XL: Bud-XL builds weight through sugar transfer from leaves to fruit, while Super-PK works through direct mineral supply of phosphorus and potassium plus amino acids.
- Versus using a higher dose of a standard base nutrient: base feeds aren't concentrated enough in PK to replicate what a dedicated booster like Super-PK delivers without unbalancing other elements in the mix.
At this concentration, Super-PK sits toward the stronger end of the PK booster market, which means careful dosing pays off more than with a milder product.
Usage guidance
Given its strength, timing and dosage matter more with Super-PK than with milder boosters.
Timing
Use during the flowering phase; for sensitive plants, Aptus recommend holding off until the fourth or fifth week of the bloom phase rather than starting from the first week of flower.
Dosage
Mix at 2.5 to 5ml per 10 litres of nutrient solution, starting at the lower end of that range and adjusting based on plant response.
pH note
Super-PK tends to raise the pH of your nutrient solution, with an ideal target pH of around 5.8; check and adjust after mixing rather than assuming your usual pH setting will hold.
Sensitive varieties
Start conservatively and watch for any signs of nutrient burn on flower sites before increasing toward the higher end of the dosage range.
Technical specifications
- Brand: Aptus
- Type: Organo-mineral PK bloom stimulator
- Phosphorus content: 20%
- Potassium content: 23%
- Additional ingredients: L-amino acids
- Size available: 250ml
- Dosage: 2.5-5ml per 10L water
- Usage window: Flowering phase, from week 4-5 for sensitive plants
- pH effect: Raises solution pH; target around 5.8
Who this is for
- Growers wanting a strong, concentrated PK boost during flowering
- Anyone who prefers a smaller, more concentrated bottle over a larger, milder booster
- Growers comfortable monitoring pH and dosage closely for best results
Best suited to plants that are already well into flowering, rather than an early-bloom starting point.
Our take
Super-PK's concentration is genuinely high for this category, which means it rewards careful dosing and punishes carelessness a bit more than a milder PK booster would. Used correctly, from mid-flower onward and with pH kept in check, it's a strong option for supporting bud development.
At a price that makes sense given how concentrated it is, this is worth a look for growers who want strength without a big bottle to store.
