Defoliation and plant training for maximum yield
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Defoliation and plant training for maximum yield

Topping, low-stress training, trellising, lollipopping and defoliation each have a different effect on the shape of the plant. This paper gives information about the effect of each method and the time to use it in the cycle of the crop. It also shows how to know when you do too much.

Canopy12 diagrams8 sources~12 min to read
In this paper
01 Purpose and scope02 Definitions03 Evidence and limitations04 Yield effects of training and defoliation05 Topping, FIM and low-stress training in the vegetative stage06 Trellising and canopy control07 Times for defoliation and training08 Troubleshooting09 Expected results and limitations10 References
Start here

Purpose and scope

Plant training and defoliation change the shape of a cannabis plant. You bend and attach branches, and you remove some leaves and branches. As a result, more of the energy of the plant goes into the flowers that you harvest.

Without training, a plant has a large height and one primary top. The bottom growth is weak and in shade, and it makes flowers that have a low density and a low value. Training makes the canopy flat and wide. The canopy is the layer of leaves at the top of the plant. Thus more bud sites get light equally.

Defoliation removes some leaves and opens the middle of the canopy. Thus the middle of the plant gets light and air, and the leaves do not stop them. If you do these methods correctly, they increase the yield and the quality. If you do them incorrectly or too much, they cause stress to the plant and decrease the quantity of flower.

  • Two groups of methods: training (to change the shape of the plant, you bend branches, attach branches and cut the growing tips) and defoliation (you remove leaves and bottom growth).
  • Make the canopy flat and level, with strong light and airflow at each bud site.
  • You do these tasks on set days in the cycle of the crop. You do not do them one time only.
  • If you do too much, there is a risk of damage. This paper shows the parts that you must not remove.
Plant without training and plant with a flat canopy1Without trainingone high cola,bottom growth inshade→2Training and spreadingbranches bentflat across atrellis→3After trainingmany tops, sameheight, light oneach siteA flat canopy changes one top that gets all the light into many bud sites at the same height.
Figure 1. In a plant without training, one top uses most of the light. The inner part of the plant stays in shade, with flowers of low density. A flat canopy after training gives strong light to many bud sites at the same height.
Who this paper is for

This paper is for each cannabis grower who wants a yield that is the same each time. Use this paper with the airflow design and mold risk papers. The work on the canopy changes the quantity of light and the airflow.

Terms

Definitions

Read these terms before the procedures. The paper uses these terms in all sections. Growers use these terms frequently, and many new growers do not know the difference between them. You do not have to know all the terms at this time. Each term occurs again, with more information.

NodeThe point on a stem where leaves and branches start. You count the nodes to measure the training (‘keep the top 3 nodes’).
ToppingYou cut the growing tip at the top of the plant. The growth in height stops, and two new tops start from the node below it.
FIMA topping that is not full: you cut most of the tip, but not all of it. This type of topping can cause more than two new tops to start.
Apical dominanceA plant usually makes one primary top that is higher than the side branches. Topping and LST stop this effect. Thus the side branches can become as high as the primary top.
LST (Low-Stress Training)You bend the branches down carefully and attach them, to make the branches flat. You do not cut the plant.
Trellis / SCROG (Screen of Green)A horizontal net. The branches become higher through the openings of the net. The net holds the branches apart, at equal distances.
LollipoppingYou remove the small branches, nodes and leaves from the bottom of the plant. The result is a bare stem at the bottom and the canopy at the top.
Defanning / defoliationYou remove some large fan leaves to open the canopy for light and air.
Fan leavesThe large leaves of the cannabis plant that absorb light. They are not the small sugar leaves in the buds.
Source and sinkA ‘source’ leaf makes more sugar than it uses. A ‘sink’ (a flower, or a leaf in shade) uses more sugar than it makes.
The parts of a plant, from bottom to top1Lollipop zonebottom third:removed→2Lateral branchesside branches,bent flat→3Nodes and fan leavestop 3 nodes stay→4Growing tipcut to make newtopsUse training on the tip, lollipopping on the bottom, and defanning on the middle.
Figure 2. The parts of the plant where you use each method, from the bare ‘lollipop zone’ at the bottom to the growing tip that topping removes.
Apical dominance, and how topping stops itthe tip hormone prevents growth of the buds below itauxin ↓side buds do not becomelarger, one top becomes highNo topping: one primary toptopping stops the hormone, twocolas startAfter topping: two primary tops
Diagram. Apical dominance: the auxin in the tip prevents growth of the buds below it. Topping removes this signal. Then two colas become the primary tops.
Quality of the information

Evidence and limitations

Three types of information

We want each paper to be correct. Thus we examine each paper for information that is not solid. This information comes from the view of one grower, from a small number of sources, or from grower methods that have no controlled test. We identify this information, and we do not show it as solid.

Frequently there is no paper for the decision that you must make. Then we use the reports of other growers and the methods that work in the rooms that we know. This information can help you, but it is not the result of a laboratory test. Use the methods that work for your plants, for your room and for your meters. If a table does not agree with your crop, use the data from your crop and record the difference.

Solid
Tests of plants, specifications or many sources that agree show that the information is correct
  • Leaves are sources of carbon. When you remove leaves, you remove capacity for photosynthesis.
  • The structure of the canopy has an effect on the light that the canopy absorbs, on the airflow, and on the risk of mold.
Grower method
Many growers use this method in their rooms. Start with it, then change it for your room.
  • Periods for topping, LST, SCROG and lollipopping that many indoor growers use.
  • Stop the removal of many leaves when flower bulking starts.
Weak
The view of one grower, a small number of sources, one test, or a method that works in one room
  • One percentage of yield increase from one defoliation procedure for all plant densities.
  • Topping on day 5 to 7 as the time for all plants. A clone starts with many nodes, and a plant from seed is different.

If you find an error, make a report. We will correct it. Make the report on GitHub, with the name of the paper and the information that is incorrect. If you have a source, include it: Make a report of an accuracy problem. The regulations, labels and licenses of your area always override each procedure in these papers. The label weak in a paper shows the points where the risk of an error is highest.

Basic information

Yield effects of training and defoliation

The basic effect is easy: more of the plant gets light and air. A flat, wide canopy has many bud sites at the same height, in strong light. Without training, one top gets all the light, and the other parts of the plant stay in shade.

You measure the intensity of light in PPFD (photosynthetic photon flux density: the quantity of light that the plant can use and that the canopy receives each second). In a flowering room, the light is approximately 400 to 800 PPFD at the start of flowering. The light increases to a maximum of approximately 1000 to 1200 PPFD in the middle of bloom.[3] This intensity increases the yield only if the bud receives the light. Thus you must open the middle of the canopy. The yield of cannabis continues to increase with higher light, up to this range, if the canopy can use the light.[3]

Target canopy light (PPFD) during the cropThe light increases to a plateau of 1000 to 1200 in the middle of bloom, then decreases at the end.03256509751300vegetativewk1wk2wk3wk4wk5wk6wk7wk8PPFD
Figure 3. A usual light curve for a flowering room: 400 to 800 PPFD in week 1, a plateau of 1000 to 1200 PPFD in weeks 4 to 7, and then the light decreases. When you open the canopy, the bottom buds also get the light of the plateau.[3]

The source and sink model shows the effect of light on a leaf. A leaf in good light makes sugar and supplies it to the buds. This leaf is a source. But a leaf in shade, deep in the canopy, becomes a sink. It uses more sugar than it makes.[2]

When you open the canopy, the leaves in shade can become sources again. At the same time, the airflow becomes better.

Sources and sinks, and the effect of an open canopy1Fan leaf in lightSOURCE: makessugar→2Sugar flowgoes to flowers→3FlowerSINK: uses thesugar→4Leaf in an open canopySINK becomesSOURCE againA leaf in light makes more sugar than it uses. A leaf in shade uses more than it makes. Open the canopy.
Figure 4. Fan leaves in good light supply sugar to the flowers. Inner leaves in shade become sinks. When you open the canopy, they become sources again, and the humidity around the buds decreases.[2]

Better airflow through an open canopy decreases the humidity around buds with high density. This directly decreases the risk of bud rot. The air can absorb only a maximum quantity of moisture. When the air has almost this maximum, it does not remove humidity from the surfaces of the plant. Thus the humidity stays around the buds.

VPD (vapor pressure deficit) measures how much more moisture the air can absorb. Keep the VPD in the range of 0.8 to 1.2 kPa. Air with high humidity that does not move, in a closed canopy, lets gray mold start in a thick cola.[6]

Results of the work
  • A flat, wide canopy lets many bud sites get the strongest light, and not only one top.
  • An open middle lets the bottom buds and the inner buds get this high light. Without the light, these buds have low density.
  • Better airflow decreases the humidity around buds with high density and decreases the risk of mold and bud rot.[6]
  • Keep the VPD at approximately 0.8 to 1.2 kPa. The airflow from defoliation helps to keep it in this range.
Training methods and the canopy that they makemore tops, same height = more light = more yieldNo training1 primary colaTopping2 primary colasLST4 primary colasSCROG8 primary colas
Diagram. Each training method changes the shape of the canopy. When the tops are more equal in height, the plants get more light. As a result, the yield is higher.
Lollipopping: keep the top, remove the bottomlight and air go to the buds with good yieldKEEPREMOVElarf and shadeRemove the bottom third (small ‘larf’ buds and shade leaves). Thus energy, light and airflow go to the top canopy.
Diagram. Lollipopping removes the bottom third of the plant. This part does not make a good yield. Thus light and air go to the buds that make a good yield.
Basic information

Topping, FIM and low-stress training in the vegetative stage

Topping and LST decrease apical dominance. With apical dominance, one top becomes high quickly, and the side branches stay behind. Topping removes that tip. Thus the growth hormones go to the side branches, and one primary top becomes two or more tops. The plant becomes wider and has more branches.[1] A test shows that the removal of the apical bud changes the parts of all of the plant where growth and yield occur.[1]

LST has the same effect, and you do not cut the plant. You bend the high middle stem down and attach it to the side. Thus the bottom branches become as high as the middle stem, and the canopy becomes level.

Because you do not cut the plant, there is no recovery time. Thus LST is the careful method that is best for new growers and for a home tent. Topping is the stronger method. It is best for longer vegetative stages or for genetics with much stretch.[8]

Topping: one tip becomes two tops1One primary topthat goesstraight up→2Cut the tipremove the topnode→3Two new topsstart from thenode belowWhen you cut the tip, apical dominance stops for the side shoots.
Figure 5. Topping removes the primary tip. The node below the tip makes two new tops. Thus the number of bud sites at that height becomes two times larger.[1]
LST: bend, do not cut1High middle stemprimary,vertical→2Bend down and attachpull it to theedge of the pot→3Level canopyside branchesbecome wide andlevelThe result is the same as topping, with no damage and no recovery time.
Figure 6. With low-stress training, you change the shape of the plant when you bend and attach branches, and you do not cut. The stress is lower, there is no recovery time, and it is easy for new growers.

In commercial rooms, the first topping is usually at approximately day 5 to 7 of the vegetative stage. Growers remove 2 to 3 nodes from plants that are much higher than the other plants. The removal makes the height the same as the height of the remaining canopy. In a usual vegetative stage of 14 days, growers do only one topping, or no topping. In a vegetative stage of 21 days, topping is the usual procedure.[8]

Select the method for the length of the vegetative stage and the height of the genetics. For a shorter vegetative stage, use LST. For a longer vegetative stage, topping is a good procedure.[8]
Height groupUsual length of the vegetative stageMethod of topping
Genetics with large height and much stretchApproximately 8 to 10 daysDo the topping at the start of the vegetative stage. Remove 2 to 3 nodes from plants that are much higher than the other plants.
Genetics with average heightApproximately 10 to 14 daysDo the topping one time at approximately day 5 to 7, or use only LST
Genetics with small heightApproximately 14 to 21 daysFrequently use only LST. Topping is not necessary.
New growers: start with LST

If you are new, do not use topping in your first crop. Use LST. When you bend and attach branches, you get most of the result of a flat canopy, and the plant does not have to recover. After you know the stretch of your genetics, you can use topping.

Topping and FIM: where you cutthe position where you cut gives the number of new topscutTopping → 2 topscut cleanly below the newestnodecutFIM → 3-4 topscut approximately 80% of thetip, not all of it
Diagram. You cut the shoot at a different position for topping and for FIM. Topping removes the tip fully and gives two tops. FIM removes the tip not fully and gives three to four tops.
Basic information

Trellising and canopy control

A trellis is a horizontal net above the table, and the plants become higher through the net. The trellis has two tasks. At the start, it holds a wide canopy in position. After this, it prevents damage to the branches because of the weight of the heavy buds. When you do the spreading of the branches, all of the table gets light. Thus the high PPFD in the middle of bloom gives a higher yield.[7]

A usual procedure is to set all three trellis layers on day 1 of flowering. The first net is 2.5 to 5 cm (1 to 2 in) below the top of the canopy. At approximately day 5 to 7, the plants are through that first net. Then the personnel do the spreading of the branches. They pull the branches away from the middle stalk and put them in the openings of the net. Thus the middle gets light, and the branches fill all of the table equally.

Three trellis layers, three tasks1Net 1 (low)spreading: lightin the middle→2Net 2 (middle)hold thebranches duringstretch→3Net 3 (high)hold the heavyweight of theflowersThe first net does the spreading. The primary task of the top nets is to hold the weight of the flowers.
Figure 7. The side of a table in the flowering stage, with three nets one above the other. The lowest net does the spreading of the canopy. The top two nets hold the weight of the flowers when they become larger.[7]
Spreading: fill each opening1Middle stalkall branches inthe middle→2Pull away from the stalkput each branchin an emptyopening→3Equal spacingeach openingfilled, light inthe middleSpreading at the start opens the middle. Thus you remove a smaller number of leaves after this.
Figure 8. From above: the spreading moves the branches away from the middle stalk into the empty openings of the trellis. Thus the branches fill the table equally, and the middle is not in shade.
  • Set all trellis levels on day 1 of flowering. The first net is 2.5 to 5 cm (1 to 2 in) below the top of the canopy.
  • At approximately day 5, the plants are through the first net. Then you do the spreading of the branches away from the middle stalk.
  • Spreading opens the middle to light and airflow. Thus you remove a smaller number of fan leaves after this.
  • The number of nets changes with the height of the plants. For short plants, use approximately 2 layers. For genetics with large height, use 3 layers.
Better spreading, less defoliation

When you do the spreading of the canopy at the start, you remove a smaller number of fan leaves after this. A table with good spreading is open to light. Thus defoliation is a small task and not a large task.

Do this

Times for defoliation and training

This section gives a procedure with times for a flowering room. Use it as a default, and adjust it to your genetics. The procedure starts with trellising on day 1. The last task is a defanning, if necessary, in the last part of bloom.

Times of the work in the flowering room1Day 1set the trellison the tables→2Day 5-14spreading withthe first net→3Day 7-10Phase 1:lollipopping ofthe bottom→4Day 21-28Phase 2: bottomdefanning→5Day 42-49Phase 3: lastdefanning, ifnecessaryThe heavy work is in the first part of flowering. The last work is not necessary, and you make the decision for each cultivar.
Figure 9. The default procedure with times for the flowering stage, from day 1 to week 7. The heavy work on the structure of the canopy is in the first part. The only task in the last part is a defanning that is not always necessary, and you make the decision for each cultivar.
  1. 1
    Day 1: Trellis
    Set all trellis levels. Put the first net 2.5 to 5 cm (1 to 2 in) below the top of the canopy.
  2. 2
    Day 5–14: Spreading
    When the plants are through the first net, pull the branches away from the middle stalk. Put the branches in the openings to fill the table equally.
  3. 3
    Day 7–10: Phase 1 lollipopping
    Remove the small branches, nodes and leaves from the bottom half or the bottom third of the plant. Keep a minimum of the top 3 nodes on each primary branch.
  4. 4
    Day 21–28: Phase 2 defanning
    Remove the bottom fan leaves on all the plants. Thus more light and air go into the inner part of the canopy.
  5. 5
    Day 42–49: Phase 3 defanning
    A last defanning, if necessary. You make the decision for each cultivar. Do it only if more light or air is necessary in the canopy for that cultivar.
A default procedure with times for the flowering room. The lollipop zone is approximately the bottom 25 to 45 cm (10 to 18 in), the bottom third. In this zone, the growth makes small larf that does not get full maturity.
Day of floweringTaskResult
Day 1Trellis (all levels)Set the structure of the canopy before the plants fill the space
Day 5–14Spreading with the first netOpen the middle to light. Fill the table equally.
Day 7–10Phase 1 lollipoppingRemove the bottom larf. It cannot make good flower.
Day 21–28Phase 2 defanningLight and airflow to the bottom and inner buds
Day 42–49Phase 3 defanning (if necessary)Only if more light or air is necessary for that cultivar
The lollipop zone1Top: keeptop 3 nodes ofeach branch stay→2Middle: defanningdefanning forlight and air→3Bottom 10-18in: removebottom thirdremoved, barestemRemove the bottom third. Keep the top 3 nodes on each primary branch.
Figure 10. Lollipopping removes approximately the bottom 25 to 45 cm (10 to 18 in), the bottom third. It keeps a minimum of the top 3 nodes on each primary branch. Thus the plant uses its energy for the flowers that get full maturity.
Do lollipopping in the first stage

Do Phase 1 lollipopping in the first week or the first two weeks of flowering. At this time, the plant can recover and send its energy to the other parts. Do not remove much of the bottom in the last stage of bloom. The removal causes damage to the plant, because the plant must make the flowers larger in this stage.

Problems to prevent

Troubleshooting

The largest problem is that you remove too many fan leaves. Fan leaves are ‘sources’: they make more energy than they use. Thus keep as many fan leaves on the plant as possible, and get sufficient light and airflow in the canopy. If you remove too many leaves, the buds do not get sufficient energy. Too much pruning can decrease the yield and the cannabinoid content, and it does not help.[2]

Too much defoliation and correct defoliation1Too much removedbare stems, lowenergy→2Selectkeep sourceleaves→3Correct defoliationopen middle,many fan leaves:ENERGY ANDAIRFLOWOpen the canopy, but keep the leaves that supply energy. More bare stem is not better.
Figure 11. Left: a plant with too much defoliation, with a small leaf area to supply the flowers. Right: a plant with correct defoliation, with an open middle and many fan-leaf sources that stay on the plant.[2]

The second problem is overcrowding. Plants that are too near each other cause a shade avoidance response. The plants sense the shade of the plants near them. Then they use energy to make the weak inner branches longer, in the direction of the light, and not to make flowers.[5] With correct spacing, much less defoliation is necessary. The canopy has a correct density from the start.

A usual start point is approximately 0.21 m² (2.3 ft²) for each plant. The usual range is 0.17 to 0.28 m² (1.8 to 3.0 ft²). A higher plant density can increase the total yield for each area, but it decreases the uniformity. Thus you cannot get the highest yield and the highest uniformity together, and there is no one ‘correct’ number.[4]

Plant spacing: density zones (sqft for each plant)Start at approximately 2.3 sqft. With less than 1.8 sqft, plants have more stretch and make shade for each other.high density: shade avoidanceusual rangewaste of space1 sqft2.25 sqft3.5 sqft
Figure 12. Spacing zones. A density that is too high causes shade avoidance.[5] The usual range is 0.17 to 0.28 m² (1.8 to 3.0 ft²). With correct spacing, you do much less work on the plants.[4]
The usual problems of new growers. In the last row, the correct procedure for a canopy with air that does not move is more airflow. It is not the removal of all the leaves.[6]
ProblemEffectCorrect procedure
Too much defoliationYou remove the leaves that supply the buds. The yield and the potency decrease.Keep as many fan-leaf sources as possible. Open the canopy only as much as necessary.
OvercrowdingShade avoidance: the inner growth is weak and has much stretchUse approximately 0.21 m² (2.3 ft²) for each plant. The range is 0.17 to 0.28 m².
Topping in the flowering stageIt causes damage to the plant when the plant must make the flowers largerDo all the topping in the vegetative stage
Heavy defanning in the last stage of bloomStress, with no time to recoverDo the heavy work in the first stage of flowering
A smell of mold, and inner leaves that dieThe canopy is too closed, and the risk of bud rot increasesFirst, increase the airflow. Do not remove all the leaves.
Leaves are not the problem

Do not continue to cut until the plant is ‘clean’. Each fan leaf that you remove supplies energy to the flowers. Open the canopy sufficiently for light and air, and then stop. If the room continues to have a smell of mold, increase the airflow. Do not cut more. Read the airflow design paper.[2]

The limits

Expected results and limitations

Training and defoliation are controls for the yield and the quality, but they have limits. The numbers change if your genetics, light or environment change. Use the data of each crop to adjust the method for the next crop. It is possible that you must adjust the method in approximately three crops of the same cultivar, to get its best yield and quality.

Adjust the method for a cultivar in three cropsSame cultivar, same room: you adjust the training and the defoliation in each crop.90102115128140crop 1crop 2crop 3yield and quality index
Figure 13. The yield and the quality usually increase in the first three crops of a cultivar. During these crops, you find the stretch of the cultivar and the quantity of work on the canopy that is necessary.

Good selection of the genetics and the spacing gives a better result at low cost. The correct number of plants and the correct layout change the yield for each area and the uniformity. The effect can be larger than the effect of equipment with a high cost, and the cost does not increase. The effect occurs because the uniformity and the light interception increase.[4][7]

  • It is possible that you must adjust the method in approximately 3 crops of a cultivar, to get its best yield and quality.
  • Good selection of the genetics and the spacing can increase the profit by 15 to 30%, and the cost does not increase.[4]
  • It is not necessary to do all the phases for each cultivar. You make the decision about the Phase 3 defanning for each cultivar, from the condition of the plants.
  • Record each crop and make photos of the canopy. Then use your data for the changes, and do not use general instructions.
  • For genetics with slow growth, use careful methods and remove a smaller quantity.
Three important facts
  1. No procedure is correct for all rooms. Start from this procedure with times. Adjust the day ranges and the quantity that you remove for your genetics, light and room.
  2. A small quantity of removal is usually better. Keep the leaves that supply the plant. Open the canopy only sufficiently for light and air, and then stop.
  3. Your camera is the best tool. Make photos of the canopy in each crop. Use these photos for your decisions in the next crop, and do not use a general method for all rooms.

Make the canopy flat, and do the spreading at the start. Use lollipopping on the bottom of the plant. Use defanning only as much as is necessary for light and air. Record your tasks. This procedure, and not one task only, gives the result of training and defoliation.

To prepare for the next stage, read the paper on harvest, dry, trim and cure. During bloom, use the mold risk paper.

Related papers
Airflow and fans
How much air to move, and where to put the fans
Mold risk
Find and stop bud rot
Harvest, dry, trim, cure
All the steps after harvest

References

  1. Sikora V, Berenji J, Latkovic D. Apical bud removal increased seed yield in hemp (Cannabis sativa L.). Acta Agriculturae Scandinavica, Section B - Soil & Plant Science. 2019;69(4):317-323. doi:10.1080/09064710.2019.1568540 https://doi.org/10.1080/09064710.2019.1568540
  2. Massuela DC, Hartung J, Munz S, Erpenbach F, Graeff-Honninger S. Impact of Harvest Time and Pruning Technique on Total CBD Concentration and Yield of Medicinal Cannabis. Plants. 2022;11(1):140. doi:10.3390/plants11010140 https://doi.org/10.3390/plants11010140
  3. Rodriguez-Morrison V, Llewellyn D, Zheng Y. Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment. Frontiers in Plant Science. 2021;12:646020. doi:10.3389/fpls.2021.646020 https://doi.org/10.3389/fpls.2021.646020
  4. Danziger N, Bernstein N. Too Dense or Not Too Dense: Higher Planting Density Reduces Cannabinoid Uniformity but Increases Yield/Area in Drug-Type Medical Cannabis. Frontiers in Plant Science. 2022;13:713481. doi:10.3389/fpls.2022.713481 https://doi.org/10.3389/fpls.2022.713481
  5. Wang X, Gao X, Liu Y, Fan S, Ma Q. Progress of Research on the Regulatory Pathway of the Plant Shade-Avoidance Syndrome. Frontiers in Plant Science. 2020;11:439. doi:10.3389/fpls.2020.00439 https://doi.org/10.3389/fpls.2020.00439
  6. Mahmoud M, BenRejeb I, Punja ZK, Buirs L, Jabaji S. Understanding bud rot development, caused by Botrytis cinerea, on cannabis (Cannabis sativa L.) plants grown under greenhouse conditions. Botany. 2023;101(5):200-231. doi:10.1139/cjb-2022-0139 https://doi.org/10.1139/cjb-2022-0139
  7. Anthony BM, Serra S, Musacchi S. Optimization of Light Interception, Leaf Area and Yield in 'WA38': Comparisons among Training Systems, Rootstocks and Pruning Techniques. Agronomy. 2020;10(5):689. doi:10.3390/agronomy10050689 https://doi.org/10.3390/agronomy10050689
  8. Morphological, physiological, and biochemical responses of two industrial hemp (Cannabis sativa L.) cultivars to different levels of topping. Journal of Cannabis Research. 2026;8:Article 410. doi:10.1186/s42238-026-00410-2 https://doi.org/10.1186/s42238-026-00410-2

Each citation in the paper, for example [1], refers to an item in this list. Each item is a primary source or an instruction from an authority, unless the item shows a different type. The results of cannabis tissue culture change much with the genotype. Before you use the dilutions, hormone doses and local regulations, make sure that they agree with the primary sources.