What it is
A PK booster is an extra fertilizer with lots of phosphorus (p) and potassium (k) and almost no nitrogen. Grow shops call them "boosters" or "bulkers". They're used on top of the flowering fertilizer, not instead of it.
What it's for
In mid-flowering, when the buds fatten up, the plant asks for lots of phosphorus and potassium. A push at that moment can give harder, more compact and better-looking buds.
When
In a short window: roughly weeks 3 to 6 of flowering (earlier in autoflowers). Before that it can't use it, and at the end it no longer needs it: in the last weeks many growers water with plain water.
Common mistakes
- Overdoing it: too much salt burns the leaf tips and locks out other nutrients (the root can't take them up). Also giving it too often or at the wrong time. "More" isn't "better": the maker's dose is usually the limit.
▲ Pros
- Denser, resinier buds: raises the grade
- In soil and in hydroponics
▼ Cons
- Only works in its window: too much or too late, and it stresses
- Doesn't add grams
🎮 Practice it in UnderGrow
It's called bloom booster and it's an optional add-on (shop › add-ons). It only works with ripeness between 30 % and 65 %: up to 3 good doses, 72 game h (3 real h) apart. Each one adds density and appearance at harvest (not grams). Outside the window or too often, it stresses.
▶ Play free