Even where cannabis is legal, in many places you are only allowed to have a limited number of plants. Those who want to maximise their yield in the face of this restriction would do best with a Screen of Green. A simple piece of netting will stimulate sideways growth and bud formation. The result: plenty of fat, highly potent buds.
Screen of Green (SCROG) is the name of one of the most efficient and productive methods of growing cannabis. It is suitable for both small home growers and professional cultivators. Basically it is a question of making maximum use of the growing area to obtain the greatest possible yield.
A mesh ensures that the cannabis plants can grow sideways in a controlled manner and with even lighting. This leads to the formation of plenty of buds. In the ideal case you will end up with a thick, even carpet of buds.
This article explains how this approach works in detail, and what you need to bear in mind.
1. The right type of plants
Before starting with the construction itself, you need to select the right types of plant. Because the growth phase lasts longer using the Screen of Green method than with other methods of cultivation, auto-flowering cannabis plants are not suitable.
Whether you start from seeds or seedlings is a matter of personal preference. Many growers prefer seedlings because they grow homogenously and their growth structure is predictable, but seeds also work perfectly well with a Screen of Green. You need to ensure that the plants grow evenly and will flower at about the same time.
Ideally, you should use either Indica, or Sativa varieties. A combination is not recommended. If you decide to go with a Sativa variety, then the pruning will involve more work, but the SCROG method is perfect for managing a cannabis variety that typically tries to shoot up.
The following varieties are particularly suitable for a Screen of Green: Michka, Silver Haze, Skunk #1, Super Skunk and Afghani #1.
2. Ideal growing conditions
It is important that the plants have enough space. In contrast to the Sea of Green approach, the pots should not be too close together. Around 30 x 30 cm per plant, or 1 to 5 plants per square metre, has proved successful. Getting a big harvest from just a few plants is one of the main benefits of the SCROG approach!
After planting in the pots, a mesh is installed between the plants and the lights. The plants will grow up to this height. Some growers construct their own netting from (hemp) ropes, washing lines, bamboo or fine wire. It is simpler to work with ready-made manufactured mesh. This comes in various shapes and sizes and is usually made of plastic, metal or nylon.
The height of the netting will be higher or lower, depending on the variety of cannabis being grown. Around 20 cm above the top of the pot is the right height for Indica varieties, for Sativa the best height is around 45 cm, and for Haze or Thai varieties the height should be as much as 60 cm above the top of the pot.
After each harvest, the net needs to be thoroughly washed or replaced.
3. The growth phase
With the SCROG approach, the focus is on the plants growing sideways. Depending on the variety of marijuana, the growth phase lasts three to eight weeks. Fast-growing Sativa varieties will reach the net sooner than Indica varieties.
Once the plants are about 25 cm high, you need to take action. The tips of the main growing points need to be pinched out. This is how you force the plants to spread sideways.
All the shoots that appear above the net need to be fixed into the mesh structure. In most cases you can simply weave them into place. Push the shoots carefully under the next hole to create a thick, even plant carpet.
It is important to avoid breaking off any side-shoots or branches, because the plant will then waste energy sending up new shoots. Very thick shoots that stretch a long way may need to be tied to the netting. The best way is to use plant ties.
The lower branches are pruned to ensure that the plants put all their energy into the upper branches, where the buds will later appear.
4. The flowering phase
Once you are happy with the horizontal growth, you can trigger the flowering phase. This is done by reducing the lighting from 18 hours to 12 hours. Growers have to decide for themselves exactly when this should take place. Generally speaking, with a Screen of Green the vegetation growth should not be pushed to the maximum, as the plant will exhaust itself producing new branches instead of forming buds.
The plant is now allowed to grow up through the netting. In order for the buds to receive the maximum amount of light, as many leaves as possible should be pushed back below the netting. If there is strong leaf growth, it is worth cutting off half the leaves. The remaining half will still provide enough energy for the plants and will keep out less light.
From approximately the second week of flowering, the buds will start to grow vertically. A thick carpet of buds will gradually develop. As the canopy becomes increasingly dense, the lower parts of the plants receive less and less light. The leaves will begin to turn yellow. At this time, it is better to cut away all the leaves, branches and buds that are below the netting.
This will ensure that the plants put all their energy into the top buds, and it also improves air circulation. This is important, as large buds in particular have a tendency to attract mould.
As with as any other intervention on growing plants, such as fertilising, great care is needed when pruning or cutting away plant material. It is better to proceed gradually. Do not remove all the branches and leaves at one time, as this may cause the plants to go into shock and stop growing normally or become sickly.
Once you master the SCROG approach, you will be rewarded with a rich harvest. Screen of Green yields can be as much as 20% higher than other forms of cultivation. Of course, some practice is necessary; there is no such thing as an instant expert.
Quick summary of the pros and cons of Screen of Green:
+ one of the most efficient and productive cultivation methods
+ up to 20% higher yields
+ high quality (only 1A buds harvested)
+ the plants do not grow too high
+ particularly well-suited for Sativa and Haze varieties
+ you only need a few plants
– Indica and Sativa varieties cannot easily be combined
– does not work with auto-flowering varieties
– the vegetation phase lasts 1 to 3 weeks longer than with the Sea of Green approach
– a netting mesh needs to be installed
- Disclaimer:Laws and regulations regarding cannabis cultivation differ from country to country. Sensi Seeds therefore strongly advises you to check your local laws and regulations. Do not act in conflict with the law.