How to Get the Best Temperature for Indoor Marijuana Plants

How to Get the Best Temperature for Indoor Marijuana Plants:

Marijuana plants grow big and strong when we provide the best temperature in the grow room. Without it, they would experience serious problems with nutrient absorption that affect their overall health. Thus, it’s important for growers to have good general knowledge and skills in controlling the temperature.

Negative effects of the wrong temperature include slower evaporation which results in less suction force. Over time, this leads to smaller roots, making it hard for plants to take in minerals from the medium.

In turn, many minerals are unused and left to break down in the root environment and build up salts. This creates high acidity in the medium which alters the roots and makes them take in less water and nutrients. Left unchecked, this condition could stop the plants from growing and kill them even before they produce buds.

Therefore, a small external problem like the wrong temperature can destroy our hopes of getting a decent harvest. So, in this article, we will learn everything there is to know how to optimize it to get an awesome cannabis crop.

How to Get the Best Temperature for Marijuana Plants

For best results, we must first learn about temperature before we start planting. Thus, this section will demonstrate the ways to achieve the ideal temperature depending on the crop’s stage in life and other factors. But first, we must understand how it affects our cannabis crop to get a clear picture of why the right temperature matters.

  • Learn the Basics
Learn the Basics

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The basics provide the framework as to why we need to provide the ideal temperature in the grow room. This includes the effects on the plants that we must avoid as well as its relationship with humidity. So, to get the best start, learn this helpful information first.

  • Effects of Temperature on Plants

How does temperature affect the marijuana plants? In general, it regulates several plant functions that are vital to growth and development. But when it gets too hot or cold, it can create devastating outcomes. The following are examples of these effects.

  • Too High

The good news is, marijuana plants don’t usually die from high heat. However, it can cause them to grow slower. Once it goes above 80 degrees, flowering will slow down, and both the smell and potency will suffer.

When it’s too hot, the plants are also less likely to fight off pests and diseases. With high humidity, they’re also more vulnerable to root rot, powdery mildew, and nutrient burn.

In rare instances, outdoor plants can suffer heat stress when the temperatures are beyond 105 degrees. Indoors, this can occur when we place the grow lights too close to the plants.

The first signs occur on the top leaves as they start to yellow and curl inward as a way of protection. If we don’t pay attention, this can devastate our crop.

So, make sure to keep the lamps a bit higher than the plants. To be safe, use a fan to blow some of the excess heat away.

  • Too Low

Photosynthesis occurs regardless of the temperature, but it likes to produce more sugar at 60ºF (15ºC) or 85ºF (30ºC). The problem sets it when it’s less than 68ºF (20ºC) because sugars move a lot slower in this temperature. In fact, it could get stuck in one place, and our plants won’t get the nourishment they need.

While older plants can recover once we improve the temperature, immature plants may not. As a result, they might stop growing and we will end up with no harvest.

During the dark period, it’s normal for the temperature to drop. But it shouldn’t drop below 60ºF (15ºC) or the plants will grow slower and produce fewer buds. Since we might not notice this if we aren’t familiar with the normal yield, it’s vital to adjust the temperature so we’ll get the most out of the plants.

  • Relation with Humidity
Relation with Humidity

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Humidity is the amount of water vapor in the air which varies depending on the temperature. Normally, the grow room has higher humidity because the plants’ leaves evaporate 90% of the water they take in.

  • Water Vapor and Condensation

Temperature plays a huge role in humidity because it affects the amount of water vapor that the air can hold. Specifically, warm air can handle much more water vapor than cold air. And we want the air to be able to hold as much water or it will start condensing.

A temperature drop will often trigger the condensation process. And we will notice this in the form of tiny droplets on the plants or on colder parts of the room.

While it seems harmless, the moisture will actually promote the growth of molds and other fungi. Therefore, we must regulate the temperature to produce less water.

  • Relative Humidity

So, what is the temperature that ensures less moisture in the garden? In general, a warm room is better since it can hold more of the vapor.

To better understand this concept, let’s use relative humidity (RH) which shows how much water vapor the air can hold. For reference, remember that the higher it is, the better it can absorb water.

So, an RH reading of 70% is great for the indoor garden. But 70% at 77 degrees is better than at 68 degrees as warmer air can hold more moisture. In this case, we must maintain the higher temperature to prevent excessive moisture.

  • Optimize the Grow Room
Optimize the Grow Room

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Internal temperature of the marijuana plants comes from a combination of factors. This includes natural or artificial light, temperature of the room, and the rate of evaporation. So, it makes a lot of sense to consider all these to optimize the temperature in the grow room.

  • Plan Beforehand

The location of the indoor garden in the building is an important factor. If we build in the basement, then it will be a lot cooler than in the attic with a flat roof.

Also, we must think of the size of the room and if we can provide adequate airflow and ventilation in it. We must also decide how many grow lights to use that would provide the optimal heat.

  • Regulate the Room Temperature

Light is the biggest source of heat in the indoor garden. Hence, we must regulate the temperature based on when the lights are turned on or off.

When we turn them on, the ideal temperature is a bit higher than during the dark period. For the cuttings and seedlings, it is between 68ºF and 77ºF (20ºC and 25ºC). For older plants, we may increase to a maximum of 82ºF (28ºC) since they evaporate a little bit more and thus need warmer temperature.

On the other hand, when the lights are off, 59ºF and 72ºF (15ºC and 22ºC) are ideal. Another important rule is that the temperature differences between day and night should have a maximum difference of 18ºF (10ºC). Thus, when it’s 82ºF (28ºC) during the day, the nighttime temperature should not go below 64ºF (18ºF).

  • Give Optimal Temperature at Different Stages of the Plant
Give Optimal Temperature at Different Stages of the Plant

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As the cannabis plants develop, they will need different temperatures in each life stage. For outdoor growers, this is less of an issue since outdoor plants can better withstand temperature fluctuations.

But for indoor growers, the perfect temperature can be tricky to maintain. Luckily, many research has helped us figure out these ideal temperatures.

  • Seedlings and Clones

Both seedlings and clones lack developed root systems, so they largely depend on their leaves to get water. Therefore, they need high humidity until their roots form fully. Hence, many growers use a humidity dome for seedling and cutting so they can easily get moisture from the air.

Ideally, the temperature should be between 68-77°F (20-25°C) with high humidity for both. At these temperatures, roots could form quickly, and our tiny plants will continue to grow to the next stage.

  • Vegetative Stage

As the young plants start to grow more leaves, they prefer a high humidity of at least 70% and temperatures between 68-77°F (20-25°C). But as they get older and their roots expand, they begin to tolerate a slightly lower humidity.

So, for the most part, the ideal temperature during the vegetative stage is between 68-77°F (20-25°C). This goes well with moderate humidity if we also make sure to provide cooler temperatures during dark periods. This will encourage bigger and faster growth.

Just don’t let temperatures drop below 59ºF (15ºC). In general, older plants are more able to survive in cooler temperatures and lower humidity during the day.

  • Flowering Stage

Once the plants start to bloom, they can thrive at a comfortable temperature with low humidity. However, if we are nourishing them with CO2, the temperature must remain under 82°F (28°C).

These lower temperatures are vital during the flowering stage as it preserves the integrity of the terpenes in the buds. To get weed that has rich taste and smell, we must make sure not to destroy the terpenes with high heat. Otherwise, we will be literally burning all the good stuff away.

So, keep the temperatures comfortable especially after week 6 or 7 when terpene production is at its peak. We can also make the temperature during dark periods slightly cooler to trigger more terpenes. This will also encourage the buds to produce more vibrant colors depending on the strain.

  • Harvesting and Curing

Half of what determines superior marijuana is the temperature during the curing period. So, continue to ensure ideal temperatures after harvest. Keep temperatures around 64°F (18°C) and the humidity at 45%. This will get us more potent and great-looking buds that produce smoother taste.

It’s also important to create air flow around the buds, but not directly on them to avoid drying too quickly. The key is to focus on maintaining the right temperature and humidity for at least 10 days. This will prevent molds from forming as well as over-drying which guarantees the best weed possible.

  • Measure the Temperature
Measure the Temperature

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Measuring the room temperature with a thermometer is not the exact temperature of the plants. However, it’s a definite indication of their health.

Hence, depending on our preference, we must use an analog or digital thermometer in the grow room. The ones with a built-in memory is a good choice as it shows the previous readings when we need to make comparisons.

To get the accurate temperature, always measure in the shade, and at various areas in the garden. Also, provide good air circulation by using fans. This will even out the temperature in the room. Aside from that, it helps stop the growth of mildew and other molds.

Since the lamps emit radiant heat, make sure they’re not too close to the plants. Otherwise, it can cause the tips of the top leaves to burn. So, make sure to provide a good distance between the two.

  • Control the Temperature
Control the Temperature

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One of the most useful skills in the grow room is getting the optimal temperature. As mentioned, when it’s too hot or too cold, our crop will most likely suffer. Luckily, anyone can master this skill. So, read on and learn the easy ways to control the room temperature for healthier marijuana plants.

  • Increase it

There’s no need to increase the temperature when the grow lights are on. As mentioned, they are the main source of heat for the indoor plants. Just make sure to use fans to distribute the air around the room and get the same level of heat everywhere. For best results, put them in swivel mode, and aim them to blow between the lamps and plants.

When the lights are off for the dark period, it can get very chilly in the grow area especially during winter. Fortunately, there are many things we can try to improve the room temperature.

First, we can use a simple space heater with a thermostat. For most growers, this solution is enough, but they can rack up huge electric bills. Alternatively, we can use a radiator with a thermostat. To avoid cold spots when the temperature is below freezing, simply introduce fresh outside air and distribute it all over the area to get rid of the problem.

  • Lower it

Since we use lamps in the grow room, heat can often become an issue. So, we must know how to choose and properly use them. For example, fluorescent lights don’t produce damaging heat and are usually great for the plants. On the other hand, HPS lamps can produce a lot heat up to 122ºF (50ºC) and can cause serious damage.

  • Use the Right Room Size

So, if we want to use HPS lights, it’s important to build the right dimension of the grow room. For a 600-watt HPS lamp always use a minimum space of 3 ft x 3 ft x 6.5 ft (100cm x 100cm x 200 cm).

  • Use Extractor Fans

For extractor fans, use the following simple formula: number of watts divided by two = extractor in cubic feet (meters). This means that 2 x 600watt HPS requires an extractor fan of 22000-cubic ft. (600m3). This equipment helps regulate room temperature by blowing the hot air outside, and sucking in fresh air.

  • Use Air Conditioners

However, if it’s hotter outside, we will also be allowing hot air into the room through the extractor fans. To combat this problem, some growers use an air conditioning unit to run as needed.

  • Run the Lights at Night

Many growers don’t have the time, money, or energy to apply the methods above. So, they simply keep the temperatures low by running the lights at night. A few hours after sunset, they turn on the lights for a few hours, then turn them off a couple hours after sunrise. In effect, the plants only get heat from the lights at the coolest period of the day.

The Best Temperatures Create Superior Weed

Marijuana plants thrive in comfortable temperatures much like humans do.
With the wrong temperatures, they can deteriorate, and we can end up with a disappointing harvest. So, pay attention if it’s hot, cold, humid, or dry in the grow area. Then makes sure to adjust the temperature to its optimal level.

To develop this skill, we must learn as much as we can about the subject. Like most excellent weed growers, we must be well-informed about the basics of temperature. In the long run, this will result in more bountiful harvests of potent buds.

So, if we care about getting great weed, we must learn to provide the optimal temperature at every stage of the plants’ life.

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