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Plant Water Temperature for Cannabis

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  • Escrito por : Ciara
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Plant water temperature is incredibly important when it comes to watering cannabis plants. It also tends to be an issue that many new growers have, although it can be something that affects even experienced growers. If you completely ignore the temperature of your water you could end up with issues that you don’t even recognize, and end up miss-diagnosing them, especially if you don’t even consider temperature when watering. In this post we’re going to talk about how to check water temperature, as well as what the perfect temp is and how to solve temperature related issues with your cannabis plants.

How to Check Plant Water Temperature

When watering, many growers tend to simply grab the hose and start. However, it’s incredibly important to measure the temperature of your water, especially if it seems to be particularly cold or warm. If the water is too hot or cold, you’re putting your plant at risk, as this can cause many different problems. In order to avoid this, all you need is a thermometer.

There are an incredibly large amount of water thermometers, and most of them are incredibly affordable. Some EC and pH meters can also measure water temperature accurately. Now that you know how important temperature is, and how easy it is to keep under control, you’re bound to start checking before every watering. Depending on the temperature, water can actually suffer certain changes in its composition, including oxygen rate.

Extreme Water Temperature Problems

pH and EC levels are some of the most important factors when it comes to watering plant; these factors are incredibly important when it comes to how your plants’ roots develop, the amount of nutrients they can absorb and the general health and state of your plants. Almost every growers knows that these two factors are incredibly important, however most of those growers often forget the third most important factor, which is water temperature. If there are wide variations in temperature, you may have some unwanted issues; water that’s too hot or cold will end up not being able to absorb certain nutrients.

Cold Water

Cold water tends to be more of an issue than hot water. This is usually because water is much colder during the winter months, especially for growers that use their own tap water. Anything lower than 15°C will cause your plants’ roots to almost entirely cease growing and can hardly absorb some nutrients such as phosphorus. This element can’t be absorbed at temperatures lower than 10-15°C, causing clear nutrient deficiencies.

The most obvious symptom of cold water is that your plants’ leaves will begin to go a dark color, similar to purple, with clear deterioration in the stem and leaves, which will also become super brittle and break easily, drastically reducing the final yield obtained.

Warm water

This problem isn’t as common as cold water, although it may happen in certain climates or at certain times of year. This factor causes your plants to stop absorbing nutrients from your water due to the lack of oxygen (the warmer the water, the less oxygen contained in it). From 20°C onwards, oxygen is reduced to around 9ppm (parts per million), with 23°C being the maximum temperature for nutrient absorption, with about 8.5ppm oxygen.

The direct consequences of warm water are the clear delay in plant growth, as well as rot appearing near the roots and substrate. This problem can signify the end of your entire grow if you don’t discover it fast enough.

The Importance of Oxygen when Watering Plants

Water is hydrogen and oxygen, although the amount of oxygen in a body of water depends on water temperature, atmospheric pressure and amount of bacteria. Oxygen helps your plants to easily absorb nutrients, allowing them to grow much stronger. This is why it’s hard to get the perfect amount of oxygen in your water without keeping temperature in mind.

Many growers get air pumps for their water tanks or nutrient tanks in order to help their plants to grow strong and healthy, however in order to do this properly you need to keep close control over the temperature in the tank.

Plant Water Temperature in Cannabis grows

Each and every plant is its own being and there’s no universal code for how you should treat every single plant. There are many different strains, each of which can be grown in different areas and climates. All of them, however, still need a stable temperature in their water – not too cold, not too hot.

If you want your plants to grow out healthy roots that can absorb nutrients, we highly recommend keeping the temperature between 20 and 25°C. The perfect temperature is 23°C, allowing for the perfect amount of oxygen. Your plants should be able to absorb the maximum amount of nutrients possible at this temperature, allowing for strong and healthy growth.

Growing in soil

When grown in soil the perfect temperature is between 20 and 23°C, keeping in mind that the soil acts as a sort of wall between the inside and outside, which allows for slight variations in the temperature in your grow room and water. The real issues start to arise when growing hydroponically.

Growing in hydroponics

When growing hydropnically, there is nothing between your plants’ roots and the water that comes into contact with them – the water is their substrate. In this situation, your plants’ roots are in constant contact with water, which is where temperature really comes into play. When growing in hydroponics, colder water (18°C) can help the roots to grow out to begin with, although not many nutrients are absorbed at this low temperature. Small plants, however, don’t need very many nutrients anyway. Once they’ve rooted and they begin to feed more, you’ll need to increase the temperature to 23°C, absorbing as many nutrients as possible while also keeping a decent oxygen ratio.

Ideal Plant Water Temperature for Cannabis Plants

Water temperature might just be one of the most important factors when it comes to healthy cannabis plants. If you follow the advice given in this post you shouldn’t have any issues keeping it balanced. Plus, there are also devices that can actually help you to adjust cold/hot water temperatures.

If you want to cool your water down, you’ll need to keep a few things in mind. Grow lights can generate high temperatures, which can cause the water to heat up. There are plenty of ways to do it manually, although this can be hard to keep up during the entire growing process. The best thing you can do in this case is to use a water cooler which can keep the temperature constant over a 24h period.

However, if you want to heat up the water, you’ll need to use a heater in your water tank. These devices can increase the temperature of your water by a few degrees, allowing your plants to absorb more nutrients from the water.

Now that you know how important water temperature is when it comes to growing cannabis plants (and plants in general) you’re aware of the issues that cold or hot water can cause in your grow. Hopefully, now you know how to easily measure your water or nutrient solution, as well as correctly oxygenate it. When done right, you can obtain some truly professional results from your plants. Let us know if you have any questions or suggestions in the comments below. Until next time!

Plant water temperature in cannabis is extremely important for the health of your plants, especially if growing using a hydroponic system.

Irrigation water temperature and cannabis cultivation

While not taken into account in many occasions, the temperature of the irrigation water (in case of using solid nutrients) or the nutrient solution (if liquid fertilizers are used) is a very important factor for proper development of the root ball and to get the most out of the plants during the growth and bloom stages, especially if hydroponic or aeroponic systems are used. Some novice growers usually forget about this and don’t even measure the temperature of the irrigation water, which normally brings problems that are in turn – in most cases – incorrectly diagnosed. Plants that don’t root as they should, with slow or even null growth and poor development of buds may all be symptoms of inadequate temperature of the irrigation water.

If we’re lucky enough to use tap water to irrigate our cannabis seeds or cuttings, we must always bear in mind the different temperatures in winter and summer, also if we’re using some type of hose in our outdoor garden. Many times, hoses freeze during the coldest hours of the day in winter, and the water during the hottest hours is not warm enough to be suitable for irrigating. On the other hand, tap water is significantly hotter in summer, also inadequate in some cases. We’ll take a look now at the problems derived from irrigating the plants with water at too high or too low temperature, also at what is the best temperature range to water cannabis plants.

This bud didn’t develop properly due to low temperatures

Symptoms of irrigation water at too high temperature

While it is a much less common problem than using cold water, in some climates or circumstances the irrigation water can be too hot. If this happens, the overall development of the plants will be slowed, since nutrient uptake is seriously compromised due a lack of oxygen in the water. These deficiencies will be almost impossible to fix unless the temperature of the irrigation water – broadly speaking, the temperature of the root area – is reduced.

Another problem that may arise, as serious as the aforesaid or even more, are fungal infections in the substrate and the root ball. While these infections can represent a major problem in the aerial part of the plant (leaves, buds, stems), they’re often deadly when found in the root area, so using water that is too hot is something that must be avoided at all times. We have different solutions to fix these problems: using air conditioning systems in the grow room is probably the best idea, although there are also water chillers that keep the temperature of the water constant, which is set by the user. Do not water the plants during the hottest hours of the day in the case of growing outdoors. Dawn or dusk (especially dawn) are the best time for watering the outdoor garden.

Always avoid excess heat in the root area

Symptoms of irrigation water at too low temperature

This is a much more common problem in many gardens, since water is at too low temperature during a considerable part of the year in many areas. One of the first visible symptoms are purple stems and petioles and very dark leaves, which is probably caused by a deficiency of phosphorous (this element is poorly assimilated at 15ºC, and won’t be assimilated at 10ºC). The growth of the plant is stopped and soon deficiencies of other elements will be observed, like magnesium or nitrogen.

During bloom, this problem usually results in poor flower development, although resin production is normal in many occasions, as happens whith intensive off-season outdoor farming. Thus, the size of the buds will be much smaller and they’ll develop much more small leaves. To avoid it, we just have to use a reservoir for our water or nutrient solution and a simple water heater, which allows us to set the desired water temperature. Using strains suitable for colder climates is also recommended if we can’t raise the temperature, like Philo Skunk, Fruity Jack or Tropimango.

The minimum temperatures of this grow were 10ºC, with the irrigation water at 15ºC

Oxygen and water temperature

As we know, water is composed of hydrogen and oxygen. But the content of the oxygen dissolved in the water is not always the same, which mainly depends on temperature and atmosferic pressure (besides other secondary factors, as we’ll see). The amount of oxygen dissolved in the water is crucial for our plants, for it determines the nutrient uptake capacity of the root system and thus the overall development of the plant. That’s the reason why many experienced growers oxygenate their nutrient solution (or irrigation water), either with air pumps and air stones, with oxygen tablets, by recirculating it or by using other water oxygenation systems. These growers know that oxygen in the water – combined of course with a suitable temperature – means better performance of the plants and thus higher yields.

The oxygen content also depends on other factors, although at a lesser degree. Significant populations of bacteria may cause a decrease in the amount of oxygen present in the water, necessary for their activity. On the other hand, water plants provide an extra supply of oxygen thanks to the photosynthesis process, although the aforementioned solutions are doubtless more usefull in our case.

You can consult the amount of oxygen (ppm) depending on water temperature on the following chart:

Temperature and amount of oxygen in water

Ideal irrigation water temperature for growing cannabis

As you’ve seen in the chart, the amount of oxygen decreases as temperature raises, although it doesn’t mean that the more oxygen the better development. We must find the correct amount, as you’ll see next. Normally, the amount of oxygen is too low for proper growth of plants at 30ºC, especially cannabis. On the contrary, we know that several nutrient deficiencies will be visible at 15ºC, so everything suggests that our ideal temperature will be between this range, 15-30ºC.

Good ambient and water temperature are crucial to get abundant harvests

Today, we know that most plants develop properly with water temperatures between 20 and 25ºC, and thanks to the experience of many growers we even know that roots develop better at temperatures around 18-19ºC. However, nutrient uptake at 23ºC is maximum. Thus, the best temperature for irrigating our plants is between 20-23ºC. Also, and apart from keeping a constant temperature with the aid of a simple water heater, remember to raise the amount of oxygen to achieve best results.

We’ll be pleased to reply any doubt or comment!

Irrigation water temperature and cannabis cultivation While not taken into account in many occasions, the temperature of the irrigation water (in case of using solid nutrients) or the nutrient