Topping a plant is a very simple process, but understanding exactly when, where and why to top a plant can be overwhelming for the beginner grower, so I’d like to share our process for topping plants here at Dirty Bird Genetics + NASC. 

How to Top a Cannabis Plant: 

You will need: A clean razor + clean hands - that’s it! 

1. Gather your sterile razor and the plant you wish to cut. 

• PRO TIP: We keep a cup of bleach near our cloning station and throw used razors into the bleach after we take cuts from each plant. We use one razor per plant and never reuse a razor when moving on to a new plant. This helps stop the spread of disease in the grow space, which often, we are not privy to until it’s too late. 

2. Take your cut off of the main stem, above an internode, but as close to the internode as you can get without harming the foliage below.

• PRO TIP: You want at least two full sets of leaves (not counting the cotyledon) before you top the plant. This will allow 2-4 new colas to develop. 

3. Now let your plant rest and recover! It’s as simple as that.

Before long, you will see 2-4 new colas emerging and developing.

When + Why to Top a Cannabis Plant 

Choosing whether to top a plant or not is a personal decision, and one that should be made with genetics and your end goals in mind. 

The primary reasons to top a cannabis plant include: 

1. Height + growth control: If you have limited vertical space, topping your cannabis plant at the right time can help the plant fill out laterally versus vertically. 

2. Yield: Each time you top a plant, if done correctly and timed correctly, you turn one main cola into 2 - 4 new main colas. Main colas, also known as apical buds, are located at the top of the plant's canopy and develop into the largest flowers on the plant. You can really increase yields on most cannabis plants by selectively topping them. You definitely don’t want to go hacking away willy-nilly. That will cause unnecessary stress to the plant. Intention and timing is key here. 

3. Even canopy: Topping and training plants can create a nice even canopy once your plants are placed into their final home for flowering. An even canopy is desirable because it allows for optimal light placement and penetration, and optimal yields.  

When to Top a Cannabis plant: 

DO: While you could feasibly top a cannabis plant once you have two full sets of leaves (not counting the cotyledon), we prefer to wait until we have 3 sets of leaves or more before topping our plants so that we don’t stress the plants out too much during their critical first couple of weeks of life. 

A freshly topped plant with several sets of leaves below the cut point. 

DO NOT: If you’re growing a photoperiod plant, we do not recommend topping or training your plant in the two weeks before you initiate flowering (12/12 light cycle). If you’re growing an auto, I wouldn’t recommend topping once you start seeing pistil development. Once flowering begins, you really want your plant focusing its energy on developing flowers, not on vegetative repair; this will help maximize yields in bloom. 

Most plants do very well topped once along the apical meristem (the main stalk of the plant). A second round of topping can be applied for larger cannabis plants with a longer veg. If you choose to top your plant again, you will want to allow the 2-4 new main-stalks to grow up large enough that there is at least one internode and leaf set to top from. 

Should I top an autoflower plant? 

Jury is out on whether topping an autoflower plant does more harm than good, and I’m certainly not an all-knowing authority on autos; however, we have experimented with this a lot in-house trying to answer this very question. In my experience, it comes down to the overall vigor of the plant. Some auto genetics are more vigorous in veg than others, and those tend to do better topped than a plant that has less vigorous vegetative growth. Height might be another consideration. If you find yourself with a tall, lanky autoflower, I think it’s reasonable to top it so long as floral initiation hasn’t begun. The slower-growing the plant is, the less I’d recommend topping because you really want all of that plant’s energy going into the growth of the plant. Ultimately, topping a plant does cause a flesh wound, and the plant will have to divert some of its energy to repairing that wound. It’s up to you to weigh whether that loss of energy is worth it. 

Sour Lime Haze x Moose n Lobsta

I hope this guide on how to top a cannabis plant was helpful to our beginner growers out there! Happy Growing, and stay tuned for more beginner friendly content to come! 

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