Flowering boosters are what you add on top of a base feed once the plant switches from growing to producing. They shift the balance away from nitrogen and toward phosphorus and potassium, which is what flower and fruit development actually consumes.
What a bloom booster does
A base nutrient is built to keep a plant alive through every stage. A booster is built for one job in one window. Most fall into three groups:
PK boosters – concentrated phosphorus and potassium, used in the middle of flower when demand peaks. The classic is a PK 13/14 style additive.
Bloom stimulants – amino acids, vitamins and plant hormones that push flower initiation early in the 12/12 window rather than feeding bulk.
Bloom stimulant, if anything. Base feed does most of the work.
Week 3-5
PK booster. This is where the demand is.
Week 6-7
Taper the PK. Finisher or hardener if you use one.
Final week
Plain water or a flush, depending on your medium.
The mistake almost everyone makes
Overdoing it. A booster is concentrated, and stacking three of them on top of a full-strength base feed pushes EC past what the plant can take up – you get nutrient lockout and leaf burn, which looks like a deficiency and gets treated with more feed. Add one booster at a time, watch your EC, and change one thing per cycle so you know what did what. Keep an EC and pH meter on the reservoir rather than guessing.
What we stock
PK boosters and bloom additives from Shogun, Canna, Athena, Buddhas Tree, Advanced Nutrients, Mills, Dutch Pro, House & Garden and Plant Magic. Pair with a base nutrient, and if you are running organic see organic plant nutrients. For the veg side of the cycle, root stimulators are the equivalent.
Flowering booster FAQs
Do I need a PK booster at all? No. A good base nutrient run at the right strength will finish a crop. A booster adds yield at the margin, and only if the rest of your environment is already right.
Can I mix brands? Yes, but not blindly. Stay within one brand's line for base plus booster if you are new, because the feed charts assume it. Mixing works once you are reading EC rather than following a chart.
PK 13/14 or a full bloom line? PK 13/14 is cheap, simple and effective in weeks 3-5. Full bloom lines give more control but cost more and need more attention.
Why buy nutrients from The Hydro Bros?
We are a hydroponics shop in Croydon and we run these products ourselves rather than reading the back of the bottle. Tell us your base feed and your medium and we will tell you what is worth adding and what is not. Discreet UK and European delivery, and excellent customer reviews on Trustpilot.
