WHAT SHOULD THE TEMP AND HUMIDITY BE IN A GROW ROOM?
The atmospheric conditions in an indoor garden have a tremendous impact on the quality and quantity of the finished crop. Growers of all skill levels are continuously trying to master the subtle environmental factors that can make a significant difference in growth and yield over the course of a plant’s life cycle.
When discussing the atmospheric conditions of an indoor garden, people are often referring to humidity and temperature. Although humidity is an important aspect, this article will focus on temperature, which plays a vital role in the way a plant is able to process light and intake water and nutrients.
Temperature affects a plant’s ability to photosynthesize, and it also plays a key role in seed germination and fruit and flower development. If temperatures fall outside the desired range, the garden becomes less efficient. Over time, these inefficiencies can lead to smaller, lower-quality yields.
How does a plant get warm?
A plant’s temperature develops from a combination of external light, external temperature, and the amount of evaporation. A plant’s exact temperature is not something you can read on a thermometer, but it is a definite measure of health.
Marijuana plants won’t usually die from being too hot, but their growth can slow from it. High external temperatures (above 80 degrees) while flowering will not only slow down bud growth but also reduce their smell and potency. If you care about growing buds with plenty of cannabinoids, you need to be sure the external temperature is kept under control during the flowering stage.
The quality of your buds is reason enough to care about temperature, but there are many more.
You also should care about their health.
Humidity is a measurement of the amount of water vapor in the air. Water vapor’s always in the air, but the temperature of your grow room effects the presence of humidity in your garden:
The first thing you need to do is to buy a hygrometer and thermometer, preferably a digital one with memory function, also showing maximum and minimum values of the past. Some hygrometers aren't the most accurate, so don’t bother having several devices in your grow room to compare values. Now that we’re able to closely monitor our conditions, we can get to the essence of humidity and temperature control – the actual humidity levels and temperatures we aim for.
The ideal temperature for clones is between 68-77°F (20-25°C) with high humidity. At these temperatures, they should quickly form roots and become more self-sufficient. These temperatures are similar for seedlings.
Remember the basic principle that warm hair holds more water than cold air? Keep this in mind, and be aware of the fact that relative humidity and temperatures interact with one another.
When discussing the atmospheric conditions of an indoor garden, people are often referring to humidity and temperature. Although humidity is an important aspect, this article will focus on temperature, which plays a vital role in the way a plant is able to process light and intake water and nutrients.
Temperature affects a plant’s ability to photosynthesize, and it also plays a key role in seed germination and fruit and flower development. If temperatures fall outside the desired range, the garden becomes less efficient. Over time, these inefficiencies can lead to smaller, lower-quality yields.
Temperature effect on plants
Plants are fairly self-sufficient, but when it comes to temperature they are at a disadvantage. Even though it is vital to their health, plants can’t create their own heat. Unlike animals and humans, a marijuana plant is entirely dependent on its environment.How does a plant get warm?
A plant’s temperature develops from a combination of external light, external temperature, and the amount of evaporation. A plant’s exact temperature is not something you can read on a thermometer, but it is a definite measure of health.
Marijuana plants won’t usually die from being too hot, but their growth can slow from it. High external temperatures (above 80 degrees) while flowering will not only slow down bud growth but also reduce their smell and potency. If you care about growing buds with plenty of cannabinoids, you need to be sure the external temperature is kept under control during the flowering stage.
The quality of your buds is reason enough to care about temperature, but there are many more.
You also should care about their health.
Humidity effect on plants
Humidity (water vapor found in the air) in a grow room or grow tent is great: it’s a sign that your plants are breathing healthily, and that there’s no lack of water throughout your grow. At certain stages of a plants life, different levels of humidity are needed so you can seed, veg, and flower the right way. But that grow room humidity level shouldn’t be more than 70% at all times, so if you’re reaching levels that high, you might want to consider where that moisture is coming from, and what you can to do prevent it from harming your grow.Humidity is a measurement of the amount of water vapor in the air. Water vapor’s always in the air, but the temperature of your grow room effects the presence of humidity in your garden:
- The higher the temperature in your grow, the more water vapor the air can hold. Heat also causes water to move faster through the air, covering more area, resulting in higher grow room humidity. That’s why when there’s lots of moisture and it gets hot (like near swamps) it gets sticky and muggy: there’s warm water all through the air moving quickly.
- The lower the temperatures are in your grow, the less water vapor air can hold. Without heat the movement of water vapor slows down, covering less area, resulting in less grow room humidity. Lower temps can be really tricky because too much moisture can result in moisture build-up and/or freezing; not enough moisture and it can get bone dry like the desert in winter.
HOW TEMPERATURES AND HUMIDITY LEVELS INTERACT
It’s important to know that humidity levels and temperatures are closely related to one another. When we talk about humidity, we usually mean relative humidity (RH), which is the ratio of partial pressure of water vapor to the maximum vapor pressure of water at the same temperature. You get the whole idea when knowing the basic principle that warm air holds more water vapor than cold air. This is one of the reasons why it’s necessary to extract a lot of warm air from our grow room, and ideally allow cool air to enter – warm air simply holds too much water vapor in it.HUMIDITY LEVELS AND TEMPERATURES: FROM SEEDLING TO HARVEST
We need to define what humidity and temperature control actually means when growing cannabis. It makes sense to divide the life of cannabis plants into 4 different stages in which humidity levels, and temperatures, should be adjusted to ensure healthy growth. Don’t think that humidity and temperature control is complicated and not worth it! It’s generally very easy, and more about keeping parameters within a certain range, and as constant as possible.The first thing you need to do is to buy a hygrometer and thermometer, preferably a digital one with memory function, also showing maximum and minimum values of the past. Some hygrometers aren't the most accurate, so don’t bother having several devices in your grow room to compare values. Now that we’re able to closely monitor our conditions, we can get to the essence of humidity and temperature control – the actual humidity levels and temperatures we aim for.
Seedlings and clones
- Seedlings and clones like high humidity levels of 65-70%
- Reason: The root system is not established
- High humidity levels allow water intake through leaves
- Temperatures with lights on: 20-25 C° (lights off: 4-5 C° lower)
The ideal temperature for clones is between 68-77°F (20-25°C) with high humidity. At these temperatures, they should quickly form roots and become more self-sufficient. These temperatures are similar for seedlings.
Vegetation Period
- The best grow room temperature during the vegetative stage of growth is 70-78 degrees F. when the lights are on during the “daytime” and no longer than 10-15 degrees cooler at “night” with a relative humidity of 45-55%.
- With these settings, your plants will be able to convert light into energy for growth. This is the time when the plant puts on branches and leaves and expands it’s root system during your growing medium. If it gets too cold or hot, growth ceases and you eventually risk losing your plants altogether.
Flowering Period
- The best grow room temperature during the flowering period of growth is 68-75 degrees during the day and no longer than 10-15 degrees cooler at night. If you’re supplementing with CO2, daytime temps are often as large as 75-82 or so. During flowering, you should lower your relative humidity to 35-45percent and even lower (30%) for the last few weeks before harvest. This will help you avoid issues with mould, bud rot and PM (Powdery Mildew) that could arise in higher humidity.
- The drying room is a place that must be carefully monitored. Bear in mind that your plants will be giving off a large quantity of moisture to the room as they dry. It’s important to pull wet air out and keep air circulating in the room without really having fans blowing right on your hanging branches, which may dry them out prematurely leading to a harsh taste and burn. Also, growers in dry areas like Colorado struggle to expand their drying time with humidifiers, while farmers in more humid climates like Northern California use dehumidifiers to pull water from the air to be able to avoid mold growing on their buds.
- The ideal temperature for a drying room is between 65 — 74 degrees Fahrenheit and humidity between 45 — 55% in a dark well-ventilated room. Cannabinoids, terpenes, and flavonoids can vanish and be released at temperatures over 80 degrees, decreasing the odor, flavor and potency of your buds. Within 6 — 10 times your branches should snap rather than bending and the buds should feel popcorn tender on the outside. This is the time to lower the person buds out of the branches and put them into glass jars to start the curing process. Heal your buds in a cool (68-72 degree F.) and dark place.
ADJUSTING HUMIDTY LEVELS AND TEMPERATURES
We’ve got a pretty good idea on humidity levels and temperatures we aim for. Now it’s time to get to the practical part, and to find ways to bring things back in balance when they’re not. Most growers will struggle to keep both relative humidity and temperatures down, which is of primary importance in the flowering period – we got that. In some colder regions, and depending on the lighting solution, the opposite scenario might be the case, and temperatures or humidity levels must be raised.Remember the basic principle that warm hair holds more water than cold air? Keep this in mind, and be aware of the fact that relative humidity and temperatures interact with one another.
WAYS TO LOWER HUMIDITY
- Run you existing tube vent on higher velocities or upgrade (air exits tent AND the room it is placed in!)
- Increase fresh/cool air supply (e.g. active air intake by 140mm case fans for PC’s)
- Try to water your plants right after lights are switched on
- Spend money on a decent sized dehumidifier (the small ones can’t hold enough water)
WAYS TO LOWER TEMPERATURES
- Just like lowering humidity: Increase the total airflow in your room by allowing more warm air to be extracted, and more cool air to enter (higher velocities or bigger tube vent)
- Always have “lights off” during the day, and “lights on” at night
- When you grow with HPS lights, consider using a cooltube
- Install an air conditioning unit (AC’s will also lower humidity levels)
RAISING HUMIDITY
- Manually increase humidity levels with a spray bottle (It won’t last long)
- Keep the surface of the soil moist, but not wet
- Hang wet towels/cloths in your grow room or put open water containers in it
- Invest money in a humidifier with a large water tank (small ones demand constant refills)
RAISING TEMPERATURES
- You can always upgrade to a bigger grow light (more watts = more heat)
- Place a heating mat at the bottom of your tent or grow room
- Isolate your grow room with materials from the hardware store
- Use a simple space heater with a thermostat
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