If you want to harvest big and resinous buds, it is necessary to pay attention to the different needs of cannabis, and there are a few of them.
One of those needs that tends to be overlooked in indoor growing is humidity. This is extremely important for the plants. It determines the development of the plants, the development of diseases and fungi, and how much water the plants absorb. Fortunately, there is not so much to learn and understand in this area. We have summarized for you everything important on the subject.
Why is humidity important for cannabis plants?
In cannabis cultivation, we talk about relative humidity. Relative humidity is how much water is in the air compared to the maximum amount of water that can be held at the existing temperature.
At all stages, the cannabis plant needs to absorb water. The amount of water it absorbs depends on the relative humidity in the grow room. If the humidity in the grow room is high, the plants will use their leaves to absorb water from the air. This in turn causes them to absorb less water through the roots. If the humidity is low, they will absorb more water through the roots.
Proper humidity in the growing room is crucial for healthy growth and good leaf development.
If you don't pay enough attention to humidity when growing indoors and it gets too high, mildew, botrytis, root rot, etc. can develop. These pathogens feel comfortable in a (too) humid environment and damage the plants partly enormously or kill them. Therefore, a breeze should always go through your grow room, which is generated by one or more swing fans, especially where the leaf-plant thicket is already very dense.
Cannabis plants need air movement through a fan at all stages. In addition, there is no way around the use of a (tube) fan with sufficient capacity if you want to grow indoors with success. This transports the air with the water outside and out of the grow room.
The supply of fresh and new air into the grow room is one of the most important ways to control humidity. The best solution is always to put the drain all the way outside from the room with the box out in the open and the supply air should come from another place outside, so it should be fresh air.
The air circulation in the cultivation room should therefore be correct, then normally no major problems arise with too high humidity. This is different when outside the humidity is very high, which is the case right now and the new air is also very humid or in hydroponic cultivation, here it is sometimes difficult to keep the humidity in the right measure and the use of a dehumidifier becomes necessary.
Electric dehumidifiers are a neat and easy thing to use if there is too much humidity in your box.
The dehumidifiers together with Humicon, the humidity controller, enable precise adjustment and control of humidity in the growing room.
At different stages of development, cannabis plants need different humidity. When they are small and young they need higher humidity, when they are older and mature they need lower humidity. If the marijuana plants do not get these conditions, they will not grow ideally and growth may slow down and be limited.
Humidity for clones/cuttings
Clones need some time to develop a root system with which they can absorb water. Especially freshly cut cuttings are strongly dependent on absorbing water from the air through the leaves. This is only possible with high humidity.
With increased humidity, the chances that the clones will form roots and grow increase. For this reason, many growers use a greenhouse for the cuttings to keep the humidity here very high. However, it should be aired several times a day, so that no fungal diseases can develop.
Humidity for young plants/growing phase
In the vegetative phase, cannabis plants form countless leaves and branches if they are in a suitable growing environment. Until the plants have fully developed their roots, they benefit from higher humidity(55% - 70%). The leaves also allow them to absorb water from the air and rapid growth is promoted.
So young plant generally grow better when the humidity is slightly higher at the same time warm temperature. This mimics the early summer.
Humidity for flowering plants
At the beginning of flowering, the relative humidity in the grow room should be lowered to 40%-50%. Some growers lower the humidity further to 30% or less as harvest time approaches. This stimulates the cannabis plant to produce more resin.
At the beginning of flowering, the cannabis plants have usually developed a complete large root system. This gives them the opportunity to meet their water needs largely through the roots and the humidity can thus be lowered. Especially in the flowering period, low humidity is important to avoid mold growth in the dense leaves and flowers.
If the humidity is too high during flowering, mold can form easily, quickly and unnoticed in the buds and destroy them or make the whole plant inedible. Even with low humidity, it is always important that air circulation is present in the grow room.
In the last 2-3 weeks before harvest, some growers use especially electric dehumidifiers to keep the humidity as low as possible. This prevents fungal diseases and at the same time stimulates the resin production of the plant. The increased dryness puts the plant under stress and it produces more resin. Some cannabis growers swear by this, although scientific proof is still lacking.
The relationship between temperature and humidity
Warm air can "hold" more water than cold air. Humidity and temperature are closely related. Both factors are crucial for successful indoor growing and should be checked regularly and regulated if necessary.
- If the humidity during the growth phase is very low and the temperature is high, this will result in stretched growth.
- If the air is too damp and cold, problems with mold and disease quickly occur.
So what to do?
- Cannabis wants a comfortable room temperature, maybe a bit warmer depending on your room temperature and a not too dry but not too humid environment. You will feel it yourself after some time. It should feel good 🙂 .
- The ideal grow room temperature is between 21°-26° C. If the lamps are off, the temperature can be lowered by a few degrees compared to the day(20°-21° C), they like that.
- Cold temperatures slow down the growth of cannabis plants. From 15 ° C the plant then stops growing completely, frosty cold temperatures can shock, damage and kill the plant.
- Avoid too cold temperatures and harvest losses with the grow room heater.
With the help of a Bar heater (also called a "heating sausage") together with a Tempcon it is possible to keep the temperature constant at the desired level even in winter.
Too high temperatures during flowering slow down flower growth and at the same time reduce the potency of the buds. So it is especially important during the flowering phase to keep an eye on the temperature in the grow room.
With a digital thermo-hygrometer, it is easy to measure the temperature and relative humidity in the grow room or to control it at different points of the growing area.
Humidity is too high - countermeasures
- Deshumidificador use. This gets the water out of the air in your grow box or grow room.
- Increase air circulation: use more or stronger fans
- Use fans with sufficient capacity, use a controller for the fan
- Do not overwater plants
- Ensure good fresh air supply
- Do not put water in the grow room or water containers, this can significantly and unintentionally increase the humidity of the air
Humidity is too little:
- Insert a Humidifier use. It brings water vapor into the air and thus increases the humidity.
Temperature is too high:
- Use more and stronger fans
- use an air conditioner
- in summer, run the lights at night so they are not on when the hottest hours of the day come.
- bring colder supply air into the grow room if possible
- Use cool tubes and heat dissipating reflectors.
- Use sufficiently powerful fan
Temperature is too low:
- a Grow room rod heater insert
- heat the room in which the box is placed
- Home mats (best used in conjunction with a Heating mat thermostat)
- use a 600W grow light in winter if possible, this will generate more heat by the way than a 400W or 250W lamp.
You can find more tips in our article on the Climate control in the growroom