Achieving the biggest possible harvest in the smallest possible grow room; that’s essentially what micro growing is about. And the cannabis plant is highly suited to that. It’s ideal if you don’t have space or a big budget for a grow room. Or maybe you just feel like carrying out a fun experiment? This article tells you all about micro growing.
Although cannabis normalisation and legalisation are gaining momentum around the world, finding clean, good quality cannabis is not always easy. This is a pity, because good quality is very important for health purposes, especially for medicinal use.
The only way to be 100% sure about the origin and quality of cannabis is to grow it yourself. But not everyone has enough space or budget to set up a good grow room. And if growing outside is not an option due to an unfavourable climate, because your neighbours won’t tolerate it or because the law doesn’t allow it, you are totally dependent on others. Fortunately, the cannabis plant provides you with more options than you think. What about micro growing?
What is micro growing?
The advantage of indoor cannabis cultivation is the ability to monitor the growing process. In a grow room, almost all circumstances can be optimised. This allows the cannabis plant to grow and flower in a perfect environment. Obviously, out in the open a plant can become quite large, because a pot hinders root formation. But at the same time you have no control over the climate outside, while you do inside. Inside, you have complete control over the light, temperature, air circulation and humidity, and of course water and nutrition. These ideal conditions are essential for a healthy plant and also for a decent yield.
Micro growing is more or less the same as regular indoor growing. There is only one major limiting factor: the available space. Which is much smaller. Really a lot smaller! Examples include a computer cabinet, an old speaker case or a small home-made grow box. The challenge is to create the optimum conditions in which to grow as many plants as possible in that small space. Or to allow one single plant to grow to its maximum size, within the limits of the micro growing space.
Cannabis plants and techniques using micro growing
The number of plants that will fit in a micro growing space depends on the size of the space and the cannabis strain chosen. The use of growing techniques to influence the size is also a determining factor.
In micro growing spaces, you should ideally opt for an Indica-dominant strain, such as our Northern Lights or Hindu Kush. Indicas remain smaller compared to Sativas. The length of an Indica also increases by 50 to 100% during the flowering phase, while Sativas undergo a 200 to 300% increase in height. So if the flowering of an Indica is activated once it has reached the middle of the growing space, it is likely that it will finish just below the ceiling.
You can activate the flowering phase of a cannabis plant by shortening the number of hours of light per day suddenly from 18 to 12 hours. Read more about activating the flowering phase of cannabis plants in this article.
A good alternative is autoflowers. Whatever the conditions, these strains remain smaller. These plants, moreover, are not sensitive to the number of light hours to activate the flowering phase. They can be placed in 18 hours of light per day for the entire cycle.
Soil quantity for a cannabis plant
But there are more tricks available to affect the size of the plant. Most plants and trees have just as much volume under the ground as above the ground. This also applies to the cannabis plant: the amount of soil which the plants have at their disposal has a large influence on their size. The available space for soil is limited with micro growing, but below is a list of averages to give an impression:
- approx. 0.5 litre: plant height of up to 13 centimetres
- approx. 2 to 3 litres: plant height of up to 30 centimetres
- approx. 5 litres: plant height of up to 60 centimetres
- approx. 12 litres or more: average plant height
Topping, FIM and super cropping
Three techniques that affect the size of the plant are topping, FIM and super cropping. With these techniques, you can influence the height of the plant to create more of a bush-like shape.
With topping, you cut or trim the highest shoot off the main stem. This stimulates the plant to create two new shoots. Instead of a single shoot growing vertically, there are now two growing horizontally. Extra buds also grow on the second shoot, which means more yield.
FIM stands for “Fuck, I missed.” The story goes that someone didn’t properly perform the topping technique and cut off the shoot too high up. When this technique is performed correctly, new branches grow in addition to the two new shoots, which generate more yield.
Super cropping resembles topping. But instead of removing a shoot, the main stem is double-folded at the top until the interior of the stem snaps. The plant ‘thinks’ that the main stem is gone, whereupon it focuses completely on the underlying branches. The broken main stem will eventually recover, but will not grow very high.
Read more about topping, FIM and super cropping.
Screen of Green
Like topping, FIM and super cropping, the Screen of Green technique (SCROG) arose from a desire to get more yield from plants. The main objective of SCROG is a uniform light distribution over all the flowers. But SCROG is also a good method to control plant height.
With the SCROG technique, a wire mesh is placed between the soil and the light source. Examples are chicken wire or similar. Once the trunk and branches grow through the screen, they are tied with thread to the wire mesh so that they do not continue to grow in length. They are instead guided over the screen. This creates a screen full of branches and tops that all remain at the same level. It’s a good way to manage the length, while all tops get the same light, which improves the yield.
Lighting in a micro growing space
In order to grow, a cannabis plant needs light, air and water. So however small the cabinet, a lamp must be present for light and heat. A lamp timer is also essential to activate the flowering phase, by switching from 18 to 12 hours of light per day (does not apply to autoflowers). The light source can’t be too large or have too much wattage. A high wattage creates too much heat in a small grow room. Be sure to hang a thermostat in the grow room. Fluorescent, CFL (energy saving lamps), HPI and HPS lamps with a very low wattage and LED bulbs are particularly popular with micro growers.
Fluorescent lights and energy saving lamps
Fluorescent tubes are inexpensive, have a good light output and their shape allows them to spread the light well. Also, fluorescent lighting is available in different light colours. A growing plant requires more blue light while a flowering plant requires more red light. Neutral light and warm white are common colours with fluorescent lamps and meet this need.
In terms of wattage, 400 to 450 Watts are required per square metre. So in a micro growing room of, for example, 60 x 40 cm (0.25 square metres) with 18 Watt fluorescent lamps, 6 lamps are needed. For additional illumination, it’s a good idea to make the ceiling reflective so that the light output fully benefits the plants. Place the VSAs outside the cabinet so that it does not overheat.
Read more about some different lighting options in a grow room.
Energy-saving lamps are almost the same as fluorescent lamps. There are a few major differences. The VSAs are built in and the glass of the lamp is folded. The range of light colours is also limited.
HPI and HPS
HPI- and HPS lamps have been favoured by indoor growers for years. That’s because they have a high light output. You can use these conventional grow lights in micro growing spaces as well, but it is not ideal. The lower wattages are harder to find and they tend to become very hot. As a result, the plants can’t be placed too close to the lamps. This requires space, which is precisely what you don’t have with micro growing.
Much can be written about LED lighting. For this article, it suffices to know that LED is ideal for all light colours. It takes up little space and is not very hot, so plants can be placed close to it. However, good LED grow lights are expensive and therefore not as cost-effective for micro growing.
Read what growers think of the difference between HPS and LED.
Water and air
The supply of water and air also calls for creativity. Water is the source of life. But plants also need fresh air. And when these lamps make the air too hot, this heat must be released.
When building a micro growing space, keep the water supply in mind. Watering from above becomes somewhat tricky at a certain point, because the cabinet is full of green buds. This is certainly true for SCROG technology. When building a micro growing space, it is therefore advisable to build the cabinet such that everything is accessible from the side. And if you want even more of a challenge, very small hydro systems are also available to be purchased.
The flow-through of fresh air is also essential. However, a table fan isn’t an option in a micro growing space. A commonly used solution is the use of two (or more) computer fans. Place the supply fan on one side and the output on the other side of the cabinet. The input should always be as low as possible, while the output should be at the top of the cabinet.
We hope that this article gives an impression of some important considerations for micro growing. It is especially important that growers realise that the first cultivation in a micro growing room is experimental. Take the time to gain experience. Find pleasure in finding out what combination of cannabis strains, growing equipment and growing techniques work for you. The reward is an educational and fun experience with the miraculous potential of the cannabis plant.
- 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.