Cannabis Training Guide: LST, Topping, FIM, Mainlining, Supercropping, ScrOG and SOG

Author: Bartholomew Alen

If a cannabis plant is simply allowed to grow straight upward, it will usually develop one dominant top with weaker side branches below it. Training deliberately changes this architecture by distributing light, space and growth across several shoots. This guide explains LST, topping, FIM, mainlining, supercropping, ScrOG and SOG, outlines the limits of every method and helps you choose a technique that suits the genetics, available space and your level of experience.

Why do professional growers bend their plants?

The answer is light distribution. A lamp illuminates the uppermost level most intensely. If a plant grows in a pyramid shape, the main top sits close to the lamp while the lower flower sites receive far fewer photons. When the main shoot is carefully guided sideways, formerly subordinate branches can rise. The result is a flatter canopy with several tops at a similar height.

Greg Green describes training in The Cannabis Grow Bible as a practical form of plant shaping: the main shoot is tied down, natural height is reduced and horizontal growth is encouraged. This is particularly useful in low rooms and beneath a ScrOG net.

Scientific studies confirm the underlying mechanism: plant architecture influences light penetration, the microclimate and the uniformity of flower development. This does not mean, however, that every intervention automatically increases yield.

What is LST?

LST stands for Low Stress Training. Instead of removing the shoot, the grower gradually bends it and secures it to the rim of the pot or to a support with a soft plant tie.

The top should not be forced into one sharp bend. Small corrections made in several stages are safer. Young stems respond particularly well because they are flexible and quickly reorient themselves.

Begin only after the plant has become securely established and developed several pairs of true leaves. Stabilize the base of the stem with a counter-tie so the root ball does not move while the shoot is being pulled. Bend the main shoot sideways, fasten it loosely and check regularly that the tie is not cutting into the stem.

Apical dominance explained simply

Apical dominance is the tendency of the uppermost shoot tip to grow more strongly than the lateral buds. Plant hormones and sugar signals work together in this process. As long as the top clearly dominates, many side shoots remain weaker.

When the top is lowered or removed, this signalling network changes and the lateral shoots gain a better opportunity to grow.

LST weakens spatial dominance without removing tissue. Topping interrupts it by removing the apical meristem. Both methods can create a flatter canopy, but they differ considerably in stress, recovery time and the risk of mistakes.

Topping: advantages, disadvantages and the right time

During topping, the active growing tip is cleanly removed above a node. The axillary buds below it will normally develop into two stronger leading shoots. This makes the plant shorter and wider.

A clean cut made with a disinfected tool causes less tissue damage than tearing or crushing.

The advantage is predictable branching. The disadvantage is the necessary recovery period: the plant must close a wound and reorganize the distribution of its growth.

A late or repeated cut can extend the vegetative stage. In short production cycles, this loss of time can cancel out the theoretical benefit.

Does topping really increase yield?

This question cannot be answered responsibly with a blanket yes. Topping does not create additional energy. The cut gives the plant neither more light nor more root space.

Instead, the intervention changes how the available resources are distributed among shoots and flower sites. A benefit appears only when the altered canopy uses the growing area more effectively, brings more flowers into a productive light zone and leaves the plant enough time to recover.

An untopped comparison plant may produce the same amount or even more. It loses no growing days and concentrates much of its development in the central cola.

In a tall room with good side lighting, this natural form can be efficient. In a low tent beneath a flat LED, however, the same architecture may become problematic: the top reaches the intensity limit early while lower areas receive too little light.

What the controlled Medusa F1 trial found

A trial published in 2026 by CRIC Labs and Royal Queen Seeds compared 48 Medusa F1 autoflowering plants. Twenty-four were topped early and 24 were left untopped.

Lighting, plant density, substrate, irrigation and nutrient supply were standardized. After 75 days, the topped plants were about ten centimetres shorter on average. Their canopies were more compact, the central flower was slightly shorter and growth was distributed more strongly across the side shoots.

The topped plants averaged 255 grams, while the control plants averaged 270 grams. At the same time, a moderate increase in cannabinoid concentration was observed in the topped plants.

The decisive point is that no statistically significant difference was found in total yield or overall harvest quality. The trial therefore does not support the claim that topping autoflowers automatically produces a higher yield.

Instead, it shows that a vigorous F1 autoflower can tolerate an early cut under highly stable conditions and develop a lower, more even canopy.

Yield per plant is not the same as yield per unit of time

A common mistake is to compare only the final weight of an individual plant. If a topped photoperiod plant must remain in the vegetative stage for an additional seven to fourteen days, it generates extra lighting, climate-control and labour costs.

A fair comparison should therefore document at least five measurements:

• Dry mass per plant
• Dry mass per square metre
• Total cultivation time
• Energy consumption
• Proportion of marketable flowers

Only this combination reveals whether the method is genuinely more efficient in your own system.

When should you not top?

During flowering

Heavy cutting during flowering is usually a poor trade-off. The plant is already investing in flower formation. Restructuring it late costs time, removes active leaf area and may delay maturity.

Light maintenance is different from removing the dominant top. Greg Green explicitly warns against using topping as a late correction.

When plants are weak or stressed

Yellow leaves, slow growth, drooping shoots or unstable roots are stop signs. Check irrigation, climate, pH and nutrient supply first.

The article Slow-Growing Cannabis Plants explains common causes; for water-related problems, consult the guide to proper cannabis watering.

With unknown genetics and no test

Different genotypes respond differently. Some produce vigorous, symmetrical lateral shoots after the cut, while others recover slowly or merely divide the same biomass among smaller tops.

Green mentions Blueberry as an example of a genotype that can respond well, but he emphasizes the influence of the variety. During a run, test only some comparable plants and record the timing, number of cuts and recovery.

When too little time remains

The calendar is just as important as the number of nodes. A plant with six nodes may look technically ready to cut but still be unsuitable if flowering is about to begin.

Commercial guides often suggest a recovery period of seven to fourteen days. This range is not a promise: temperature, root health, genetics and the severity of the cut determine when growth actually accelerates again.

FIM or topping?

FIM is the incomplete removal of the young growing tip. Instead of cleanly cutting away the entire apical meristem, only a large portion of the fresh tip tissue is removed.

Depending on the cut and the plant's response, several new shoots may develop. That same variability is also the disadvantage: FIM is less predictable than a clean top.

Mainlining and manifolding

Mainlining combines repeated topping with symmetrical tying. The goal is a central hub from which several equivalent main arms extend.

After every planned cut, the number of leading shoots theoretically doubles. The system looks tidy and makes an even canopy easier to achieve, but it requires time, consistent maintenance and a plant that tolerates cutting well.

The method does not suit every schedule. If flowering must begin quickly, several recovery periods may provide no net benefit.

The available window is also narrow with autoflowering plants because the onset of flowering cannot be postponed at will. Scientific literature on mainlining explains the hormonal and structural principles while also pointing to the lack of standardized protocols across genotypes.

Supercropping: controlled pinching and bending

During supercropping, a still-flexible shoot is carefully rolled between the fingers to soften it and is then bent without intentionally tearing the outer skin.

The technique can bring excessively tall shoots down to canopy height. It is considerably more invasive than LST and requires experience. Too much pressure may sever vascular tissue or cause an open break.

If a branch breaks accidentally, align it immediately and secure it with plant tape or a splint. Greg Green explains that many breaks can heal when they are stabilized properly.

Cleanliness and mechanical stability are more important than home remedies. Honey appears in older growing guides but is not a standardized sterile wound treatment.

ScrOG: Screen of Green

In a ScrOG, a net is installed above the plants. During the vegetative stage, growing shoots are not simply allowed to pass upward through it; instead, they are guided sideways into empty squares.

The net is therefore a guidance system, not merely a support frame. The method combines LST with area planning and is particularly suitable for a small number of plants spread across a broad growing area.

Do not completely fill the net before initiating flowering. Many genotypes stretch considerably afterwards. The amount of empty space that should remain depends on the expected stretch.

A sativa-dominant plant often needs more reserve than a compact indica. For background on the basic growth forms, see the comparison of Indica, Sativa and Ruderalis.

SOG: Sea of Green

SOG follows the opposite strategy: many smaller, uniform plants with a short vegetative stage and little individual shaping.

The aim is a closed, uniform surface of dominant main shoots. Clones are attractive for this purpose because genetically uniform starting material can grow more consistently. Plant density, air movement and legal plant-count limits must nevertheless be considered.

More plants do not automatically mean a higher yield per unit of area. Research shows that density and architecture work together. Overcrowded stands may reduce uniformity and create a poorer microclimate.

Topping autoflowers: an exception, not a standard rule

The traditional recommendation is not to top autoflowers because their vegetative window often lasts only a few weeks. This cautious approach remains sensible for beginners.

The Medusa F1 trial nevertheless shows that the question is more nuanced: under optimal conditions, a vigorous, uniform F1 autoflower can tolerate an early top without a statistically significant reduction in final yield.

This does not mean that every autoflower should be topped.

How to conduct a useful comparison

Grow reports are valuable only when the other influencing factors remain as constant as possible. Two plants raised from different seeds are not a clean comparison because different phenotypes can strongly affect growth and yield.

Genetically identical cuttings or a highly uniform F1 population are better options. Place the test and control plants in comparable positions, or rotate them according to a fixed plan.

A photograph taken from the same position every week is often more informative than a memory at harvest. Record the working time as well: mainlining can create an even canopy, but it requires considerably more tying and supervision than a naturally growing plant.

Recommended plants and cuttings for training

The following recommendations are starting points rather than guarantees of a specific response. Begin with gentle training and document internodal spacing, lateral-shoot vigour and recovery time.

Hazelightyear seed-grown plant

A Haze-dominant genotype is an interesting candidate for LST or ScrOG when long shoots and pronounced stretch need to be distributed across the available area.

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Real Killer Skunk cannabis cutting

A cutting provides genetically uniform starting material. This makes comparative trials easier when one plant is trained only with LST and a second is topped.

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Studio 54 pre-grown cannabis plant

The established bushy structure provides several points for gentle tying. Before every intervention, check that the plant has fully recovered from transport and transplanting.

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Kushblast Kush cannabis cutting

With more compact genetics, early and careful LST can help bring the side shoots to the same level. Strong interventions should wait until visible acclimatization has taken place.

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More varieties and current availability can be found in the Cannabis plants and cuttings category. Guidance for the first days after delivery is available in the Grow Island Blog.

Which method suits which genetics?

Long, flexible shoots

LST and ScrOG use the length of the shoots without removing unnecessary tissue. Leave reserve space for the stretch.

Compact, heavily branched plants

Gently spreading the side branches may be sufficient. Too many cuts quickly make an already dense canopy difficult to manage.

Photoperiod plants

They provide more recovery time because the transition to flowering can be controlled. This makes topping and mainlining easier to schedule.

Autoflowering plants

The short, genetically determined window favours gentle LST. Topping is defensible only on highly vigorous plants and with sufficient experience.

The labels indica and sativa offer only a broad expectation. The actual phenotype, internodal spacing and lateral-shoot growth are more valuable for choosing a method.

Observe the real plant rather than relying only on the variety description. For colour-related or genetic characteristics, see Why Cannabis Turns Purple.

Four traits matter more than the label

A decision path for beginners

1. Is the plant healthy and active? If not, do not train it.
2. Is vegetative time limited? Choose gentle LST instead of repeated cuts.
3. Is vertical space limited? Plan LST or ScrOG early.
4. Are several identical cuttings available? Set up a controlled comparison.
5. Are the genetics unknown? Begin with a small bend and document the response.
6. Is flowering about to begin? Do not start structural mainlining.

Common cannabis-training mistakes

Doing too much at once

Topping, heavy defoliation, transplanting and introducing a new lighting schedule on the same day make the cause of later problems impossible to identify. Change one major factor and allow time for observation.

Ties that are too tight

Stems thicken. Wire or thin string can cut into them and interfere with sap flow. Use broad, soft ties and inspect every fastening regularly.

Training without a lighting plan

A flat canopy is useful only when the area is illuminated evenly. Insufficient distance can cause light stress despite a good plant shape. Guidance on symptoms is available in LED Distance for Cannabis.

Excessive defoliation

Leaves are photosynthetic surfaces. Do not remove healthy fan leaves indiscriminately. Scientific evidence shows that architectural manipulation can locally improve light and uniformity, but severe cutting costs active meristems and leaf area.

Read the separate guide to cannabis defoliation.

Ignoring mould risk

A dense, flat canopy can block air movement. Monitor humidity below the canopy and between flowers. The guide to identifying and preventing mould explains the warning signs.

Checklist after every intervention

During the next 24 to 72 hours, pay particular attention to new growth. Old mechanical damage will not disappear, but new shoots should look vigorous.

If yellow leaves, spots or burnt tips appear at the same time, avoid making a hasty fertilizer correction. First use the diagnostic guidance in Nutrient-Related Problems.

Conclusion

LST is the best starting point for most beginners because it is reversible, gradual and easy to observe. Topping creates predictable branching but requires a healthy plant and sufficient recovery time.

FIM is more variable, mainlining particularly structured, supercropping demanding, ScrOG area-oriented and SOG density-oriented. No method replaces a stable climate, suitable lighting, healthy roots or a realistic assessment of the genetics.

A professional approach does not involve using every technique simultaneously. Choose a clear objective, change little, document the response and compare only plants that began in a similar condition.

Sources and technical basis

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