Mastering Plant Training: Topping vs. Fimming

In this blog we explore one of the most talked-about—but often misunderstood—topics in horticulture: topping and fimming.

If you’re serious about plant health, yield optimization, and canopy management, understanding these techniques is critical. Let’s dive into what they are, how to use them, and what to avoid—especially with autoflowers.

What Is Topping?

Topping is a pruning technique that involves removing the apical bud (the plant’s main top shoot). This bud normally suppresses the growth of side branches due to high concentrations of auxins (growth hormones). Once removed, the plant redirects energy to the lateral nodes, encouraging two new shoots to grow—ultimately multiplying the plant’s flowering or fruiting sites.

Benefits of Topping:

• Increases number of colas (tops)
• Encourages bushier growth
• Helps maximize canopy space
• Boosts yield when done correctly

Pro Tip:
Topping works best with photoperiodic plants—never try this with autoflowers, as it can drastically reduce their yield.

What Is Fimming?

Fimming, or as it’s politely called, “F**k (Flip) I Missed,” is a less aggressive version of topping. Instead of removing the entire top, you trim just part of the new growth—often leaving about a third of it intact.

The result? Growth is stunted temporarily, and lower branches have a chance to catch up, creating a more even canopy.

Key Differences from Topping:

• The top may regrow in a mutated form
• Ideal for managing plant height
• Less risk of shocking the plant

Pro Tip:
Fimming is great when your plant is getting too tall too quickly or when you want to improve lower growth structure without halting upper development entirely.

When NOT to Use These Techniques

Some plants don’t respond well to topping or fimming. Here’s when you should steer clear:

🚫 Do NOT Top or FIM Autoflowers
Autoflowering varieties operate on a biological clock that can’t be paused. Any stress—like pruning—will delay growth without delaying flowering, meaning smaller yields and weaker plants.

Is This Super Cropping?

Not quite—but it’s related. Super cropping involves strategically stressing the plant to improve strength and shape, such as bending or pinching stems. Topping and fimming fit under this broader umbrella as architectural training techniques aimed at creating the optimal plant structure for light exposure and airflow.

Other training techniques discussed in past episodes include:

• Knocking & Niching
• Girdling & Scoring
• LST (Low-Stress Training)

Final Thoughts

Topping and fimming are powerful tools in a grower’s toolkit—but only if used intentionally and correctly. When done right, these techniques enhance yield, structure, and plant health. When done wrong—especially on autoflowers—they can cost you the whole crop.

So before you snip that apical bud, ask yourself:

• Is my plant a photoperiodic variety?
• Am I aiming for better shape, better yield—or both?
• Do I have the time to let the plant recover?

And if you are looking for an excellent fertilizer to help out with growing your plants from seed to harvest, check out Liquid Gold

Article by Dr Russell Sharp

If you would like to keep up to date with subjects just like this, you can listen to both our podcasts! Links can be found bellow:

Hydroponics Daily Podcast: https://open.spotify.com/show/207T7p7fw9sPjINfSjVXW2

Cereal Killers Podcast: https://t.co/eSEbBkTVHl