What are the optimum humidity levels for indoor cannabis growing? Full Guide 2020 Updated
What is Humidity?
Humidity is expressed as the quantity of water vapor in the air. Humidity plays a necessary role in influencing how much evaporation occurs in cannabis plants. Your plant will take in more nutrition and water when the humidity is low. If for any reason the evaporation strain gets to be too much, marijuana plants will guard itself against scarcity by closing its stomata. So naturally this will stunt the growth of your plant due to the lack of water absorption.
Humidity is an important topic for cannabis growers. But why is humidity so important for cannabis plants, and what are the ideal humidity levels to maintain in your grow room?
To better understand why humidity is important to plants, it helps to think about how plants absorb air from the environment. Remember, all plants respire carbon dioxide from the environment through their leaves. In doing so, they naturally lose some of the water retained in their foliage.
Plants have different needs at each stage of the growing cycle, so to keep it simple, we’ve organized the grow stages into four parts and each one is defined below.
Cloning
Because cannabis cuttings root best in warm conditions with high humidity, the cheap trays with clear plastic domes work remarkably well. In cool conditions, a heat mat should be placed underneath the trays to maintain an optimum temperature of 74-78 degrees F. and relative humidity at 75-85%. No matter where and into what medium you plan to root your clones, keep warmth and high humidity on your priority list. Clones allowed to get cold or dry will perish quite quickly. Too much humidity (over 90%) can also cause mold and rot, so cut a quarter-sized hole or two in your clear plastic dome to allow some air movement and circulation.
VEGETATIVE GROWTH
Young cannabis plants will grow most vigorously if you can maintain 50-70% RH; ideally, for the duration of the vegetative growth phase. Mother plants will also perform best in high humidity environments. Low humidity, even without excessively high temperatures, can stunt plant growth. A dry microclimate is to be avoided at this stage.
FLOWERING STAGE
Once your cannabis is flowering you will want to consider dropping the RH greatly. This is in order to reduce the risk of the dreaded rot. You ideally want you grow room to have a relative humidity of 40-50% now.
Keeping track and controlling your marijuana grow tent humidity is important if you want to really get the most out of your plants. It is another important factor that is usually overlooked by less experienced cultivators. Now that you have a better understanding of its impact you should be able to utilize the knowledge to improve the quality of your grow.
The Late Flowering Stage – 2 Weeks Before Harvest
This is a stage which many people do not consider, but weed plants to have an early flowering period and a late flowering period. The late flowering period starts roughly 2 weeks before the weed plant is ready to harvest.
Now, this is not totally necessary, and you can by all means leave things the way they are, as we discussed in the flowering section above. The temperature and humidity levels for the flowering stage, as indicated above, will do fine for the late flowering stage as well.
However, if you really want to get the best yields with the highest potency, you will want to make some more changes here. In order to increase THC quantity, potency, and the final yield, you should aim to bring the humidity level in your grow room down to 30%.
How to Control Humidity?
Thermo Hygrometer 2 in 1 Meter: Measures both humidity and temperature of the air. Many digital models can even store previously collected measurements that can be transferred to a computer for additional analysis and careful record keeping.
Humdifier for Plants: These are used in the first four weeks to promote vigorous seedling/cutting growth for improved yields later. Also, because outside air is used to refresh grow room air, areas with very arid outside conditions can benefit from a humidifier or series of strategically placed humidifiers throughout the growing cycle.
Dehumidifier for Plants: No commercial-sized grow room is complete without a handful of dehumidifiers on hand. Smaller grow rooms should be no different but the cost ratio of production to equipment expenses can sometimes lead to tough decisions being made. Most grow rooms typically deal with an excess of humidity at one time or another, so if corners are being cut this is probably not the place to do it as lowering humidity during flower/late flowering stages has a big impact on density, flavor and potency of the ripened buds.
Controlling humidity is tough because it changes in relation to temperature. Wily RH values can be crazy-making, but with the right equipment and careful assessment, you can optimize growing conditions and maximize your yields.
Humidity is expressed as the quantity of water vapor in the air. Humidity plays a necessary role in influencing how much evaporation occurs in cannabis plants. Your plant will take in more nutrition and water when the humidity is low. If for any reason the evaporation strain gets to be too much, marijuana plants will guard itself against scarcity by closing its stomata. So naturally this will stunt the growth of your plant due to the lack of water absorption.
Humidity is an important topic for cannabis growers. But why is humidity so important for cannabis plants, and what are the ideal humidity levels to maintain in your grow room?
To better understand why humidity is important to plants, it helps to think about how plants absorb air from the environment. Remember, all plants respire carbon dioxide from the environment through their leaves. In doing so, they naturally lose some of the water retained in their foliage.
Plants have different needs at each stage of the growing cycle, so to keep it simple, we’ve organized the grow stages into four parts and each one is defined below.
Cloning
Because cannabis cuttings root best in warm conditions with high humidity, the cheap trays with clear plastic domes work remarkably well. In cool conditions, a heat mat should be placed underneath the trays to maintain an optimum temperature of 74-78 degrees F. and relative humidity at 75-85%. No matter where and into what medium you plan to root your clones, keep warmth and high humidity on your priority list. Clones allowed to get cold or dry will perish quite quickly. Too much humidity (over 90%) can also cause mold and rot, so cut a quarter-sized hole or two in your clear plastic dome to allow some air movement and circulation.
VEGETATIVE GROWTH
Young cannabis plants will grow most vigorously if you can maintain 50-70% RH; ideally, for the duration of the vegetative growth phase. Mother plants will also perform best in high humidity environments. Low humidity, even without excessively high temperatures, can stunt plant growth. A dry microclimate is to be avoided at this stage.
FLOWERING STAGE
Once your cannabis is flowering you will want to consider dropping the RH greatly. This is in order to reduce the risk of the dreaded rot. You ideally want you grow room to have a relative humidity of 40-50% now.
Keeping track and controlling your marijuana grow tent humidity is important if you want to really get the most out of your plants. It is another important factor that is usually overlooked by less experienced cultivators. Now that you have a better understanding of its impact you should be able to utilize the knowledge to improve the quality of your grow.
The Late Flowering Stage – 2 Weeks Before Harvest
This is a stage which many people do not consider, but weed plants to have an early flowering period and a late flowering period. The late flowering period starts roughly 2 weeks before the weed plant is ready to harvest.
Now, this is not totally necessary, and you can by all means leave things the way they are, as we discussed in the flowering section above. The temperature and humidity levels for the flowering stage, as indicated above, will do fine for the late flowering stage as well.
However, if you really want to get the best yields with the highest potency, you will want to make some more changes here. In order to increase THC quantity, potency, and the final yield, you should aim to bring the humidity level in your grow room down to 30%.
How to Control Humidity?
Thermo Hygrometer 2 in 1 Meter: Measures both humidity and temperature of the air. Many digital models can even store previously collected measurements that can be transferred to a computer for additional analysis and careful record keeping.
Humdifier for Plants: These are used in the first four weeks to promote vigorous seedling/cutting growth for improved yields later. Also, because outside air is used to refresh grow room air, areas with very arid outside conditions can benefit from a humidifier or series of strategically placed humidifiers throughout the growing cycle.
Dehumidifier for Plants: No commercial-sized grow room is complete without a handful of dehumidifiers on hand. Smaller grow rooms should be no different but the cost ratio of production to equipment expenses can sometimes lead to tough decisions being made. Most grow rooms typically deal with an excess of humidity at one time or another, so if corners are being cut this is probably not the place to do it as lowering humidity during flower/late flowering stages has a big impact on density, flavor and potency of the ripened buds.
Controlling humidity is tough because it changes in relation to temperature. Wily RH values can be crazy-making, but with the right equipment and careful assessment, you can optimize growing conditions and maximize your yields.
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