Material for informational purposes only. Growing marijuana and hemp (without a permit) is prohibited in Poland as well as in some other countries. Check the regulations in your location and the required permits in order not to break the law if you want to grow restricted plants.
In order for our plants to grow healthily we need to provide them with appropriate, stable living conditions.
We need to control the temperature and humidity and make sure that light doesn't get in when our plants are 'sleeping'. For our safety it's also important that the light doesn't get out when the plants are having a 'day', and that the smell doesn't get out.
The easiest way to control the conditions is to keep the grow room closed off, either in a grow room or in a grow tent, commonly called a growbox. In addition to tents, there are also cabinets prepared for cultivation available on the market.
Growboxes (tents / cabinets) are prepared to hang lamps, filters and fans. Their walls are sealed to let no light in or out, and on the inside are lined with various types of reflective materials to fully exploit the potential of cultivation lamps.
What a plantation must contain?
Lighting is usually MH lamps, HPS lamps or modern LED lamps. Alternatively CFL, CMH/LEC or Plasma lamps. The lamps have to work a certain amount of time per day depending on the phase the plants are in so you will also need a timer to turn the lamps on and off.
Air exhaust fan with carbon filter to control temperature and eliminate plant odor.
A fan that blows air.
A thermometer so we know if our ventilation is regulating the temperature efficiently.
A hygrometer so we can more accurately control humidity.
If necessary an air heater, air conditioner, humidifier or dehumidifier. If we are forced to invest in these additional devices, it is worth thinking about controllers that will synchronize their work to automatically maintain the right conditions for the health of our plants.
Pots, soil and fertilizers containing nutrients for healthy development of our plants.
The little things we can't forget are hooks/ropes/chains to hang lights, fans and air filters, and ventilation ducts to let the air out of the box.
The next step may be the systems that automate the cultivation - soil irrigation systems or hydroponic systems to grow plants without the use of soil, but if this is your first time to focus on lighting and ventilation, do not complicate matters.
HPS lamps - High Pressure Sodium
HPS lamps hit the market in 1964, the main application was street lighting.
Probably still the most popular lamps in plantations, but recently LED lamps are gaining popularity.
HPS lamps are efficient and their light colour is optimal for the flowering phase. They can easily be used during the whole cultivation period, including the growing phase.
MH lamps - Metal Halide
These lamps give off a very bright white light and are most commonly used on playing fields and stadiums. The first stably functioning MH lamps were developed in 1962, but came into widespread use a few decades later, when it was possible to reduce the cost of their production.
In plant cultivation they are usually used during the growth phase due to their light color, and during the flowering phase the plants go under HPS lamps.
MH and HPS lamps have the disadvantage that they require an additional reflector and igniter and generate high temperatures, which translates into the need to install stronger ventilation systems. Competition are the LED lamps, but their price is several times higher than the MH and HPS lamps, and require 'learning' the lamp to fully use it.
Some people use MH and HPS simultaneously throughout the grow period to provide even better light color for their plants, but most people will get great results with just the HPS lamp.
Examples of the distance from the top of the plants and the area that can be optimally illuminated with a lamp of a given wattage:
Always do a simple temperature test to see if the lamps are too close to the plants: place your hand, palm down under the lamp, just above the tops of the plants. If after 30 seconds you start to get burned, then the plants will also be too hot. If the distance is optimal, it is worthwhile to improve the temperature control in order to be able to place the lamps at the right distance and get maximum yield.
The farther away the lights are from the plants, the more area they will illuminate, but more distance means less light, smaller yields and more plants stretching upwards. If you want to illuminate a larger area, use a wider reflector so you can still keep the lamps close to the plants.
CMH/LEC lamps - Ceramic Metal Halide/Light Emmiting Ceramic
LEC is a registered trade name, CMH is a type of lamp, but so many people say LEC (like sneakers on athletic shoes) that in growshops almost always this type of lamp has both designations at the same time to make it clear what is meant, so CMH, LEC and CMH/LEC are the same thing.
Just like the sun, CMH lamps produce UV-B rays, which increases trichome production and improves plant smell. Glass blocks UV-B rays so don't use glass-enclosed reflectors on these lamps, let the rays shine directly on the plants.
Always wear eye protection against UV rays when using these lamps on your plants.
The downside of the CMH/LEC lamps are a lower yield than HPS lamps of the same wattage, but they give a higher yield than MH lamps when used during the flowering phase.
Another plus is that their life is much longer than HPS lamps.
CMH LEC lamps should usually be hung about 45-50cm above the plants in the case of 315W lamps and about 60-66cm in the case of 630W lamps, but usually does not mean always so check by putting your hand under the lamp - if after 30s starts to burn you, give the lamp higher. Also, check the manufacturer's recommendations as some models have a suggested distance of 70-90cm from the tops of the plants.
Just like MH and HPS lamps, CMH lamps need an igniter (ballast), but there are many CMH lamps on the market with built-in ballast which makes them more convenient to use than lamps with a separate igniter.
LED lamps have been gaining popularity for several years. Their quality is increasing and prices are decreasing. Manufacturers are improving the color of the light and use better lenses, which translates into deeper light penetration and higher yields.
LED lamps generate a much lower temperature than HPS lamps so it is much easier to control growing conditions. On the other hand, the leaf temperature is lower so you must take this into account when setting the temperature and humidity in the box.
Harvest quality according to many growers is noticeably better (power, taste and smell).
They do not require a starter, you buy, hang, plug in and you can work.
The biggest disadvantage is the price, a good lamp can cost 300-500 euros for a power of about 200W to 1000-2000 euros for 600W lamps.
The other downside is that they often need to be mounted higher above the plants than HPS lamps, which requires more available height on the plantation, and grow tents are usually only 150-200cm. This is not due to the temperature, which is low, but simply the power of the leds. This problem often builds up slowly, over weeks, so it's hard to notice right away (leaves turn yellow, dying very slowly). Always check the recommendations of the manufacturer of the lamp as to the optimum distance from the plants. There are already LEDs on the market that can be hung close to plants.
Another minus is that the lamp is not equal to the lamp, with the same power will differ in light color, temperature that they generate, the distance from the plants that they require so each LED lamp you have to learn from scratch to optimally use it.
LED lamp should have a full spectrum of light, and not as in the old LED lamps only red and blue LEDs.
When buying a LED lamp pay attention to the fact that it has a full spectrum of colors and real power. Many manufacturers state the 'equivalent of 600W HPS'. The truth is that the LED lamp, depending on the model and skills can be drawn 0.5-1g per watt, so if you want the equivalent of 600W HPS buy a LED lamp with similar, real power - usually have a parameter given real power consumption in addition to the inscription xxxW HPS equivalent.
Air circulation, filters and fans that is temperature control, humidity and odor neutralization.
Air extraction fan + carbon filter
These are one of the most important things in our plantation. They help eliminate odour and control the temperature. In addition, the plants need fresh air, it is assumed that the fan should exchange all the air in the box at least once every 1-2 minutes (some sources say once every 3-5 minutes, but this is usually not enough to maintain an adequate temperature, always better to have a reserve power).
A carbon filter attached to the fan reduces its efficiency by about 25%.
Fans are given in m3/h. So if we have a box with dimensions of 1.20m x 2.40m x 2.5m, we have an area of 7.20 m3. We want to exchange air once a minute or 60 times an hour, so we calculate 7.2 x 60 = 432 m3 per hour. The filter will lower the efficiency of the fan so we make a correction: 432 + 25% = 540m3/h.
Is a 540m3/h fan enough for us? To exchange an optimal amount of air yes, but whether to control the temperature we do not know. We do not know what lamps you will use, with what power and in what quantity. We do not know where you live, what temperatures are in the room where you will set up your tent/grow box. Will it be in the attic in summer or in the basement in winter? You need to take into account the ambient conditions.
There needs to be a duct connected to the fan that will lead the warm air out of the room the tent is placed in - this route should be as short and straight as possible. The longer and more winding the greater the loss of efficiency of the fan.
The longer and more winding the path, the greater the loss of performance of the fan. You also do not want the fan to run non-stop at maximum speed, it will wear out faster and break down more easily.
You need to take all this into account, if the tent is located in a cool room, you are using a LED lamp and next to it there is a chimney, to which you can connect a ventilation pipe, the power reserve does not have to be huge. If you are using HPS lamps, the room is moderate in temperature, and the ventilation duct has a long and winding way before it reaches the window or chimney then the power reserve will have to be considerable.
Unfortunately it's hard to guess, many sites and stores say buy such and such a fan for such and such a growing area and that's it, but then there may be an unpleasant surprise.
You have to take everything into account when shopping, and you'll find out the truth anyway once you've got the lamps and ventilation running. It is better to buy ventilation with a reserve of power, because buying a weaker and thus cheaper fan can prove not only a lack of savings because you will have to buy a more powerful fan, but also a waste of time it will be necessary to remove the weak fan and filter and connect the new one.
Remember that the carbon filter also has a given capacity, so if you buy a fan and filter too weak, you will have to change both - or you can buy a second set and connect it instead of pulling the first. Buy a filter with a higher power than the fan to have a reserve, as it will be weaker than the fan it may not work and let the smell through.
To the fan should be bought controller, which will measure the temperature and regulate the speed of the fan, so it will not work at maximum, but only in an optimal way. Controllers usually have the option of specifying the minimum rpm, below which we do not want to go down even if the temperature is low because we want to maintain an optimal flow of fresh air.
There are many fans on the market with an option of manual or automatic speed control, so you may be able to buy two in one, without having to buy a controller.
In addition to a fan that blows air out, it's a good idea to place (hang) fans that blow air into the box to avoid hot spots that can harm plants. This will also allow you to 'rock' the stems slightly, which will definitely strengthen them.
Suggested temperature and air humidity are given further on in the text - it may turn out that the temperature surrounding our tent is so high or so low that despite efficient ventilation an air conditioner or air heater will be needed. Also air humidity may need to be adjusted with a humidifier or dehumidifier.
Our plants like a similar temperature to us of 20-30 °C. In the first phase (growth/vegetative phase, lamps 18-20h/day) the temperature can be in the upper limit.
In the flowering phase (lamps 12/day, and for autoflowering plants from the beginning to the end 18-20h/day) the optimal temperature is 18-26°C.
A temperature below 15°C can cause negative effects, not always noticeable, but the yield can be lower than with plants that had optimal conditions.
During the day (lamps on) keep the temperature at the upper limit, at night (lamps off) keep it at the lower limit.
In the growth phase it can reach 60%, but should not go below 40%.
In the blooming phase it should be kept at a level of 40-50%, and in the last weeks of blooming 40-45%. Too high a humidity can end up with mould on our flowers.
It is absolutely necessary to buy a thermometer and a hygrometer - preferably two in one. You can buy an electronic one with a sensor on a cable - hang it near your plants.
On the market there are also devices controlling simultaneously ventilation, heaters, air conditioners etc... For the first time you don't have to invest in everything to the maximum, start with mastering ventilation and air filtration, with time, as the need arises, invest in other solutions, if it will have its justification.
Sometimes, harvesting 10% more in a small tent may not be worth investing in a few expensive devices and professional controllers.
If the air is enriched with carbon dioxide, the temperature should be about 5°C higher, and if you use very bright lamps such as LEDs, the temperature can be even higher, and with a combination of powerful LED lights and carbon dioxide and low humidity, the temperature should reach 35°C.
We will not elaborate on CO2 because this is a text about basic, minimal equipment, but it can be mentioned because you will probably come across it in many texts on the Internet.
Information on air humidity, thermperature and CO2 in the case of using LED lamps:
- https://www.thriveagritech.com/avoid-this-common-mistake-when-comparing-leds-to-hps/ https://www.thriveagritech.com/how-is-co2-supplementation-affected-by-converting-to-led-lighting/ https://www.lumigrow.com/learning-center/blogs/optimize-your-cannabis-grow-for-led-temperature-and-co2-considerations/
To sum up for the first time you need:
- a sealed room/tent/box for lighting and a timer to automatically turn on the lamps for 12-20h/day depending on the phase in which the plants are in an air extraction fan with a carbon filter, preferably with speed control to more easily control the temperature thermometer + hygrometer fan blowing air
In addition, only if clearly needed:
- air conditioner humidifier or dehumidifier professional climate controllers CO2 generator
Once you have a plantation where you can control the conditions, it's time to add pots, soil and fertilizer.
For the first time there is no point in getting too complicated and experimenting with special growing media, hydroponic systems etc. Just pots, good soil such as Biobizz Light-Mix, one fertiliser for the growth phase and one fertiliser for the flowering phase (e.g. also from Biobizz or BioCanna).
Everyone has his or her own preference as to the number of plants, so on the internet you will find very different suggestions, from 4 plants per square metre in 20-40L pots to 12 plants in 7-10L pots.
Taking these different suggestions into account I think it would be wise to use 10L pots and between 6 and 9 plants per square metre to start with before you develop your own growing style.
E.g. faster, smaller plants 9 per square meter, larger, longer maturing plants 6 per square meter.