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The Best Bud Boosters 2025

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If you've been growing for a while, you know that the flowering phase is everything. You can have good growth, good genetics, excellent light… but if you don't use flowering boosters properly, the buds stay loose. This is where Bud Swellers come in. 

In this guide you'll find everything you need to understand how they work, when to use them and which one to choose depending on what you're looking for. At Growlobby we have the best bud swellers at incredible prices, we explain what they are and show you our 2025 selection. 

What is a bud sweller? 

A bud sweller is a flowering stimulator designed for the fattening phase. Its objective is clear: to increase the weight, density, amount of resin and size of the buds. 

Many use phosphorus and potassium (PK), others use sugars, enzymes or amino acids. Some go gentle, others are proper powerhouses. 

The important thing is not to throw them all in at random, but to know which bud fattener to use, when and how to combine it with the rest of your growing plan. 

Cannabis bud

The Top Bud Swellers of 2025

Here's a quick rundown of the best bud fatteners we've been selecting. 

We know what you're looking for. Fat, resinous, heavy buds that smell from the door. And for that, you need to use a bud sweller like you mean it: 

Bud Sweller and Booster Comparison Table - Growlobby 

Product  Type / Main Action 

When to use? 

 Organic? What does it provide?
Bloombastic – Atami High PK + bio-minerals + sugars + activators  Weeks 3 to 5 of flowering No Fattening, resin, flavour
Top Max – Biobizz  Organic stimulator (humic/fulvic acids)  Throughout flowering Yes  Resin, flavour, improves uptake 
Bud Candy – Advanced Nutrients  Sugars and carbohydrates  Throughout the cycle (growth and flowering)  No  Sweet flavour, aroma, improves texture 
Delta Nine – Cannabiogen Biostimulant + enzymatic activator From 8 days before flowering to week 4  Yes  Resin, essential oils, active metabolism 
Heavy Bud Pro – Grotek  Mineral PK for density and firmness  Weeks 4, 5 and 6 of flowering No Fattening, compaction 
More Grams – Cannaboom PK + enzymes for final fattening  Weeks 5 to 8 of flowering  No  Volume, density, resin 
Bio-Heaven – Biobizz  Amino acids for uptake and vitality  Throughout the crop Yes Improves uptake, reduces stress, vigour 
Sugar Daddy – Technaflora  Sugars + calcium + magnesium  Throughout the cycle (growth and flowering)  No  Flavour, nutritional balance, structural improvement 
Monster Bloom – Grotek PK 50-30 highly concentrated  From appearance of pre-flowers to harvest No  Extreme fattening, weight, compaction 
Green Sensation – Plagron  PK + sugars + enzymes + defensive boost  Weeks 4 to 7 of flowering   No  Fattening, resin, flavour, overall plant health 
Sweet Grams Plus – Trabe  Finaliser with carbohydrates Last 10–15 days of flowering  Yes  Final flavour, aroma, improves drying 

Cannabis flowering

Which Bud Sweller to choose? 

Organic growing? → Top Max + Bud Candy + Bio-Heaven 

Looking for volume and density? → Monster Bloom or More Grams 

Want ease and results? → Green Sensation 

Top flavour finish? → Sweet Grams Plus + Bud Candy 

Safe fattening without overdoing it? → Bloombastic + Sugar Daddy 

When to use the Bud Sweller: stage-by-stage table 

Growing stage  Recommended products 
Pre-flowering (8 days before)  Delta Nine (foliar) 
Start of flowering  Delta Nine (via watering), Bio-Heaven, Sugar Daddy, Bud Candy, Top Max 
Bud formation (weeks 3–4)  Bloombastic, Top Max, Green Sensation, Heavy Bud Pro, Bio-Heaven, Sugar Daddy, Bud Candy 
Fattening (weeks 5–6) Monster Bloom, More Grams, Heavy Bud Pro, Green Sensation, Bud Candy, Sugar Daddy, Top Max 
End of flowering (weeks 7–8)  More Grams, Green Sensation, Bud Candy, Top Max, Bio-Heaven 
Last 10–15 days  Sweet Grams Plus, Bud Candy 
Throughout the crop  Bio-Heaven, Sugar Daddy, Bud Candy 

Practical tips to get the most out of your Bud Swellers 

  • Monitor EC/pH with each dose, especially if you're using mineral versions or mixing multiple brands. 
  • Watch how the plant responds: sometimes less is more, adjust doses if leaves yellow or show signs of excess. 
  • Adequate ventilation, lighting and correct humidity (40–50%) help prevent mould and support good fattening. 
  • Keep genetics in mind: some plants fatten later (weeks 7–8), while others show signs from week 5. 
  • Don't combine several strong PKs at once. Choose one. 
  • Always flush the roots at the end if you use mineral products. 
  • If you use organic fatteners, you don't need to flush, but don't overdose either. 

Unsure between two products? Want us to help you make a fattening schedule based on your genetics and base fertilisers? Write to us and we'll sort it out with you. 

Get the best out of your plants with the Bud Swellers we have at Growlobby, take advantage of our offers and fatten your buds like never before.