Topping cannabis: how to do it, when and why?

The basics of topping cannabis

Cannabis topping is often done once the cannabis plants has developed between 3 and 5 nodes. It’s worth adding that many of those that practice cannabis topping routinely prefer to wait for at least 5 nodes to have developed before removing the tip.

At this stage, the plant has gained sufficient strength, stature, and root size to survive the (high) stress of cannabis topping. Often your cannabis plant will be around 4-5 weeks old at this stage but be aware that different cannabis strains grow at different rates in the first few weeks.

The cleaner and sharper the blade the better. A blunt blade may leave a ragged cut which may cause more harm than good. A razor or sharp horticultural scissors are ideal.

Using a sharp blade, the growing tip is removed between the 3rd and 5th nodes. Aim to cut a few mm above the side branches to avoid damaging the small shoots that are positioned between the main stem and the side branches. These small side shoots will eventually take over from the main bloom and grow with increased vigour.

Some growers will also top these side shoots, but wait a week or two before you attempt it. This will give you four main tops instead of the original one.

What are the effects of topping for indoor cannabis growers?

You will see a shorter, bushier cannabis plant. Instead of the central main bloom being the tallest point of the plant you will see a flatter canopy. For indoor growers this allows the main bloom points to form a more level canopy with more of the blooms in the optical ‘sweet spot’ of optimum PPFD (light) levels.

This allows more efficient utilisation of the light for indoor growers. Instead of just your main central bloom forming under optimised light levels you may find that several of them are now bathing under ideal light levels.

Look forward to some heavier cannabis harvests! Remember that un-topped cannabis plants have a single central bloom, whereas topped cannabis plants can have two ‘new’ central blooms (or perhaps 4 if you have topped twice).

Related:
The ultimate guide to growing cannabis indoor

What are the benefits of topping for outdoor cannabis growers?

Some outdoor marijuana growers find that certain cannabis strains (e.g. the stretchiest sativa strains) can simply grow too tall. Sativa cannabis seeds can produce plants that reach 3-4m tall.

If you’re growing in a garden or patio this could be inconveniently tall and too easily noticeable. Topping these cannabis plants once or more is a great way to control vertical height.

Related:
The ultimate guide to growing cannabis outdoor

Topping vs Super cropping cannabis

Power Plant ready for harvest after 5 toppings and some super-cropping.

Two cannabis grow techniques that have similar sounding names (but very different processes) are topping and super cropping. Topping your cannabis plants means careful removal of the growing tip in order to produce a shorter, bushier plants with more growth points.

Supercropping is the name given to the technique where the stem of the cannabis plant is gently crushed between thumb and finger. The softened stem can now be bent over horizontally at 90º and tied in position to prevent it reverting to vertical growth. Supercropping is used by both indoor and outdoor cannabis growers to reduce vertical plant height. It also allows you to put several bud points at an equidistant position from an indoor grow light. This can be beneficial for the subsequent yields.

Lollipopping is another term with a similar sounding name which shouldn’t be confused with topping. Lollipopping is the removal of lower branches which may only produce small fluffy ‘popcorn’ buds. By removing these branches, air flow beneath the canopy is improved and the plant can focus its energy on the main upper blooms.

How does cannabis topping work?

Cannabis plants exhibit a property called apical dominance. This determines the classic Xmas-tree style growth pattern that follows when a cannabis seed is germinated. It’s an evolutionary adaptation to the fact that the sun moves from one side of the sky to the other allowing the plant to grow well without parts being permanently in the shade.

The growing tip of the main central cannabis stem is known as the apex which is where the name apical comes from. This top part of the plant produces plant growth hormones known as auxins which flow downwards through the phloem – this is the stem tissue which transports sugars etc from the leaves.

Auxins prevent excessive stretching (elongation) of the growth-points below the apex. Auxins, however, don’t travel long distances through the plant. Therefore, as the plant grows vertically, the lower branches are released from the inhibiting effects of the auxins. This produces the classic “Christmas tree” shape.

Cannabis topping enables the manipulation of growth patterns by removing the top apical growth tip where auxins are produced. Breaking the apical dominance, as professional cannabis geneticists refer to it, allows side branches to develop. Once the tip of the cannabis plant has been removed the two adjacent side shoots grow rapidly over the following week. Other cannabis training techniques such as manifolding and mainlining can be made easier when cannabis topping is used.

Why top cannabis plants?

Not everyone believes in cannabis topping. Plenty of cannabis growers prefer the simplicity of growing cannabis naturally without any growth techniques.

After all, cannabis has grown well that way in nature for thousands of years. Furthermore, some cannabis strains (such as a stretchy sativa) may be much more suited to topping than e.g. a naturally compact and short indica.

But those that do practice cannabis topping often find that it allows them to grow strains which might otherwise be too tall and stretchy to grow indoors. For some indoor cannabis growers, topping cannabis may seem easier and more convenient than using the SCROG method.

Related:
Growing cannabis with the screen of green method (SCROG)

Other growers like cannabis topping because it allows them to cultivate their cannabis plants with more blooms growing under optimised light levels due to the flatter canopy. This allows them to produce heavier yields than otherwise possible.

Is LST or topping better for cannabis?

Both LST (‘low stress training’) and cannabis topping are based on the same principle of manipulating plant height/growth in order to maintain a more even canopy. This level canopy is then able to bathe in the optical sweet spot of your light. The SCROG method also utilises the same principle for the benefit of the grower.

Both LST and cannabis topping are popular with growers that need to reduce plant height e.g. to allow stretchier strains to fit in a low-height indoor grow room.

Whether cannabis LST or cannabis topping is better may well depend on the preferences of the grower. Some growers fundamentally feel that cannabis topping is wrong.

For some growers high stress training is something they simply don’t like to do. For that reason they prefer low stress training (LST) where branches are tied down with e.g. cable ties to a metal screen. Other growers don’t like the fiddly high-maintenance nature of LST and prefer to top their plants once or twice instead.

Related:
Growing cannabis with the low stress technique method (LST)

Fimming vs topping cannabis

Topping and fimming have similarities. Both involve the removal of the growing (apical) tip of the cannabis plant. However, topping is deliberately done to allow the two adjacent side shoots to replace the apical shoot.

Fimming is still an attempt to increase the number of main blooms. But instead of two you could end up with 4 or more. Just like cannabis topping, a ‘fim’ will shock and stress the plant which require a few days to recover. Again, wait until you have at least 3 and perhaps 5 nodes.

Fimming is where you remove around 75% of the tip instead of the whole thing. Instead of a clean cut through the stem (as with cannabis topping) you deliberately cut through the base of the tip leaving a rough (and perhaps messy looking) patch of vegetation beneath. This can then gradually grow back with perhaps 4 or more growth points.

However fimming is regarded by many as a precise science than cannabis topping. It doesn’t always work and the word FIM is thought to originate from the words (F**k I missed), which infers a low-success process.

Best cannabis strains for topping

In general, few cannabis seed companies recommend the routine topping of autoflowers. That’s because autoflowers have a fixed life cycle, typically around 75 days. The process of cannabis topping is stressful to the plants requiring several days to repair and reconstruct. Many autoflower seed growers feel that autos simply lack the right plant genetics for cannabis topping. Instead, many prefer to grow autoflower seeds the natural way.

If you do find the need to grow your autoflowers with a more level canopy of blooms (e.g. if you have stretchy sativa autoflower seeds) then LST or SCROG could be preferred methods.

Many strains grown from photoperiod indica feminised seeds don’t really require topping. That’s because the genetics are often naturally short, squat and bushy with little stretch during bloom. Often these types of cannabis plant are somewhat easier to manipulate and manage in the grow room using simple LST methods such as tying down taller blooms or perhaps using the SCROG method.

However, cannabis topping is often very useful for sativa strains or stretchy sativa-leaning hybrid strains. Sometimes for indoor growers, cannabis topping is the best way (perhaps the only way) to allow a harvest if space is limited.

When to top cannabis?

Traditionally the advice has always been to wait until you have 3-5 nodes on your cannabis plant before you top it. Some repeat users of cannabis topping even suggest to wait until you have 5-6 nodes. The main message is not to attempt cannabis topping on an immature seedling.

Topping cannabis early

If done too early, cannabis topping can permanently stunt the subsequent growth. Allow the cannabis plant time to establish a good root system and vigorous growth above ground with healthy looking leaves. If in doubt, allow your plant time to grow a little larger before attempting to top it.

Topping cannabis twice

After you have topped your cannabis plant you will notice the two adjacent side shoots will grow upwards rapidly. These will replace the main bloom. However, each of these can also later be topped.

This will produce 2 new shoots from each side shoot. Instead of having a cannabis plant with a single main bloom you would now have 4. This process can even be repeated again if required.

How to top cannabis plants tutorial

Cannabis topping isn’t a complicated process, you won’t need much equipment, time or experience.

• Use a new razor blade, or some very sharp horticultural scissors. You want to make a clean cut as opposed to a damaging rough cut.
• Ensure your cannabis plant has at least 3-5 nodes, often that means around 30 days from cannabis seed germination.
• Carefully slice through the main stem of the cannabis plant and discard the tip. Aim to cut the tip well above the side shoots on the node just below so as not to damage them. These side shoots will soon grow rapidly with the growing tip removed and the apical dominance broken.