There is a common misconception that high-pressure sodium (HPS) lights are required for dense, or thick, cannabis buds. This is unequivocally false. There are a number of factors to producing dense buds but using inefficient HPS lights is not one of them. Not to say you cannot get density with HPS, but it certainly is not required.

Grow Indoors

Unless you live in an ideal climate for growing cannabis you will not get dense buds from growing cannabis outdoors. That is almost a guarantee in Canada unless you are running an extended lighting greenhouse. Outdoor cannabis plants have to contend with cloudy days, bugs, and typically too short of a growing season.

Provide Enough Light

One of the main factors is making sure you have enough light. To produce thick cannabis buds I recommend 35-40 watts/square foot. This metric only applies to printed LED boards and not other types of light or LEDs.

There is another myth that “COB style” LED pucks produce denser buds because the light is more concentrated. Having run these side by side with printed LED boards I have found this to not be the case. If anything the puck style lights are more likely to cause light burn/scorching.

Use Deep Water Culture Instead of Soil

There are many advantages to Deep Water Culture (DWC) over soil and other methods such as coco. One of the advantages is increased nutrients availability. In veg this translates to a faster growth rate, for example hydroponic farmers can turn over a head of lettuce in 1 month vs soil growers where it can take 2-4 months. This study found that with growing lettuce hydroponics methods offered 11 times greater yield.

During flower growing in DWC results in denser buds, as there is greater availability for nutrient uptake. Not to say you cannot grow dense nugs in soil, but hydro certainly does not hurt.

Strip & Spread

Strip & Spread is an essential technique for getting dense flowers.

Strip – refers to stripping all lower growth from the plant. This allows the plant to focus its energy and resources on the top of the canopy. The bottom buds are typically useless loose flower anyways.

Spread – refers to spreading the buds apart. This is usually done using a trellis/scrog system. Being spread apart encourages the flowers to grow outward, making them denser. This goes hand in hand with not overvegging your plants as discussed below.

As a rough measure, you want about 4 colas per square foot. if your goal is dense nugs and less trimming work then remove any competing growth during early flower.

Do Not ‘over-veg’ or overcrowd your Plants

Flowers that are crowded together will not grow as densely as those that are spread apart. This goes in line with the spread technique above. This is why it is important to not over-veg your plants. The time to flip your plants from vegetative (18/6) to flower (12/12) varies on the strain, but expect them to double in size throughout flower.

If you are trying to grow dense buds, the above is an example of over-vegging. The plants should be flipped 1-2 weeks earlier and trimmed more aggressively (limiting the total number of colas) to get something more like the canopy on the right

The results speak for themselves:

Left Side: Overveg’d crowded buds. Right Side: Early flower and more aggressive trimming

The yield of the ‘overveg’ was slightly higher than when employing methods for producing dense buds, but there was exponentially more work for trimming as well. I much rather end up with denser flowers and sacrifice 5-10% yield (which is mainly in stem weight anyways).

Quality Genetics and Indica Dominant Strains

As always genetics are very important. Do not skimp on seeds, it is not a place where you want to cut corners.

Indica plants are known for their short stubby genetics. Sativa, on the other hand, tends to stretch and produce fluffier buds. If you’re looking for rock-hard dense buds, you’ll have a better chance with Indica dominant strains of cannabis.

I’ve noticed a direct correlation between leaf thickness and bud density. The stockier your leaves during veg, the denser the bud. The opposite is true for long stretchy leaves that tend to produce scraggly looking flowers.

CO2 Supplementation

This is not absolutely required but will certainly increase your flower density if you are running above 35 watts per square foot with a Printed LED Board. If you have read my article on DIY CO2 supplementation you will know that the CO2 I pump into my grow box is a happy by-product of the beer brewing process.

It is no coincidence that the densest buds are the one right next to my co2 output.