Why Do Plants Sweat? Here’s why and what you can do


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The water drops on the plants’ leaves in the morning are not always dewdrops. Some water drops are the result of plant sweating. Similar to humans, plants also sweat for multiple reasons which aids in the cooling process. 

Sweating in plants is caused by transpiration, which is the movement of water through the plant to the leaves. Plant sweat or guttation is the secretion of water droplets from the pores of the leaves and is used as a cooling mechanism. When the water evaporates from the leaves, heat is removed providing a cooling effect.

In this article, we will give a rundown of why plants sweat and whether it is normal or not. We will also discuss how to effectively increase the humidity around your houseplants to keep them healthy all year round.

What Causes Indoor Plants To Sweat? 

What causes Plants to Sweat

Two natural phenomena in plants can cause your plants to sweat (drip water): transpiration and guttation

Transpiration is where water absorbed from the soil is lost in the form of water vapors. 

However, in guttation, the excess water and minerals are lost in the form of droplets. Both guttation and transpiration cause your plant to seem as if they are sweating. 

Transpiration

Indoor plants are a great way to improve indoor temperature, humidity, eliminate air pollutants, purify the surroundings, reduce dust fall, and carbon dioxide. 

These positive improvements aren’t only done by the photosynthesis and respiration process of indoor plants. 

Transpiration also plays a significant role in improving the indoor environment and it involves water transportation from the root to shoot and leaves. 

As we know, the roots of the plants are responsible for absorbing the required water and nutrients from the soil. By means of osmosis, the roots hair of your indoor plants sucks up water from the soil. 

Minerals and food are transported to the various parts of plants via the phloem. Whereas excess water is transported to the aerial parts (stems, petioles, leaves,  flowers, etc) of the plants through the xylem. 

Plants continue to draw up available water from the soil throughout the day. However, not all the water sucked up from the soil is used by the plants. 

Only a small percentage of absorbed water is utilized by the plants. Similar to humans, plants also sweat to evaporate excess water.  

This process of evaporation of excess water is called transpiration. 

The extra water is lost into the environment, in the form of water vapors. This natural process of plants makes them effective for adjusting humidity indoors.

Misting is a good way of increasing the humidity around your plant as well as for watering lightly without the effects of overwatering. You can try this misting bottle from amazon which is cheap, durable, and gets the job done.

misting can amazon

Does Transpiration Also Occur at Night?

You might notice your plant dripping water or sweating even at nighttime. Most people get worried as they think transpiration in plants only occurs in the daytime. However, it is not the whole truth. 

According to professor of plant ecology and physiology, Todd E. Dawson, and professor of botany and plant sciences, Louis Santiago, from the University of California, the common assumption that transpiration does not occur at night is false. 

Dr. Todd E. Dawson and Dr. Louis Santiago provided substantial evidence in their research paper that the process of transpiration continues even at night in various plants. 

Leaf stomata do not close completely, leaving a space for water vapors to evaporate. 

“As the stomata are already open and photosynthesis in plants can start as soon as the sunrises, nighttime transpiration may boost carbon fixation in plants during early hours of daylight”, stated Dr. Todd E. Dawson. 
[Google Scholar]

Dr. Dawson also stated, “Nighttime transpiration is widespread in many plant species including indoor plants. Nighttime transpiration also may specify a significant part of plants’ day-to-day and seasonal water use. 

Nighttime transpiration is common especially for low-light indoor plants because they mainly depend on sun flecks for the process of photosynthesis from low-light environments which depend, for photosynthesis, on sun flecks 

Therefore, if you notice your plant sweating or dripping water at night, don’t panic as it is a completely normal process. 

What Factors Can Increase Sweating (Transpiration) in Plants?

The effectiveness or rate of the transpiration process in plants depends on the temperature, humidity, vapor pressure deficit (VPD), strong wind, radiation, light, plant species, and other internal factors. 

Transpiration rate can be affected by both abiotic and biotic factors. 

Humidity

The spaces between cells in the leaf are normally saturated with water vapor. When the air surrounding the plant is dry, water vapors in the spaces between cells diffuse more rapidly out of the leaf. 

The rate of transpiration will increase if the air surrounding the plant is dry. 

However, if the air surrounding the plant is moist or humid, the transpiration rate will decrease. Your plant will sweat (drip water) more in a less humid environment as compared to when it is placed in an area with a noticeable level of humidity. 

Solution:

Using a humidifier can significantly increase the humidity around your plant.

The Geniani portable humidifier from amazon provides the ideal environmental humidity for healthy plant growth. You can find it by clicking here.

geniani portable humidifier

Temperature

Transpiration depends on the phenomenon of evaporation. A rise in temperature outside the plant will increase the rate of evaporation. 

As a result, the rate of transpiration will also increase. 

Your plant will also sweat more if the temperature of the leaf is high to cool down its inner temperature.  

Both outside and inside temperature significantly affect the rate of transpiration. 

Solution:

The simple solution to this, is to move your plant to an area where it is not being hit directly by sunlight. 

If the plant is close to a wall that is being hit by light it can also reflect heat onto the plant. Moving the plant will also help in this case.

Strong Wind

When the air surrounding the plant is still, the process of transpiration makes the air surrounding the leaves moist or damp. 

The water vapors build up and increase the air humidity. 

As we mentioned earlier in the article, if the outside air is dry, the transpiration rate will increase to moist the outside air. 

Similarly, during a windy day, the moist or damp air surrounding the leaves gets blown away, taking the humid air away and leaving dry air behind. 

The plants will increase the rate of transpiration to make the air around the leaf moist again. 

The stronger the wind is, the higher will be the rate of transpiration. 

However, if the wind is very strong around the leaves, leaf stomata may close as the guard cells lose too much water. Your plant may sweat or drip more water during dry windy days. 

Solution:

Plants that are close to doorways and windows or even out in the yard can be subjected to high winds that significantly reduces humidity. Moving the plant to a less windy area will help reduce moisture loss to the wind.

Light

Light affects the rate of transpiration as it can significantly affect the size of the stomatal openings in the leaves. 

During the night or in shade, the stomatal opening may partially or completely close down, reducing the transpiration rate. 

However, on a very sunny day, the stomatal opening on the leaf gets wide open, increasing the rate of transpiration. 

Furthermore, to reduce the heat from the plant during hot weather, water vapor rapidly moves outward, cooling the leaves. This also helps the plants from being scorched by the hot harsh sun. 

Your plant may be sweating more to remove the inner heat of the plant and preventing its leaves from being burnt in the sun. 

Solution:

Try to provide some type of shade for your plant by placing them around larger plants if they are outside or by moving them to an area where they are not being hit by direct sunlight.

Indirect sunlight is the best in such cases. See our article 7 safe places to put plants at home.

If you feel your plants are not getting enough light you can use this cost effective grow light we use from amazon.

Providing balanced lighting is crucial, and we have found an effective and durable artificial grow light on amazon that provides the right spectrum of light to get the job done. You can find it by clicking here.

grow light

Transpiration Vs. Guttation:

Both transpiration and guttation can cause your plant to sweat or drip water. However, both these natural processes are two different phenomena.

Down below, we have made a table to give you a better understanding of what exactly makes transpiration and guttation different from each other. 

TranspirationGuttation
In transpiration, the absorbed water from the soil is lost in the form of water vapors.In Guttation, the excess water, minerals, and salt are lost in the form of droplets.
In transpiration, only pure water is evaporated into the outside air.In guttation, the removed droplets also contain various minerals and salts along the water.
In transpiration, the water is lost through three aerial parts of the plant: stomata openings, lenticels present on shoots, and cuticles.In guttation, droplets are removed through pores, aka hydathodes, present at the ends of the veins.
Transpiration can significantly affect the turgidity of the leaf, leading the leaves to wilt. Guttation has no apparent effect on the turgidity of the leaves.
Guard cells present in the stomata are responsible for regulating stomatal transpiration.However, the opening and closing of pores, aka hydathodes, can’t be regulated.
Transpiration mostly occurs during the daytime, in the presence of sunlight.Guttation, on the other hand, mostly occurs at nighttime or during the early hours of the sunlight. 

Is Sweating a Good Thing?

Sweating or guttation does not cause any harm to a plant and it does not mean that the plant is stressed in any way. Sweating is a natural process caused by either transpiration or guttation where water forms droplets on the leaves, giving the plant a sweating appearance.

Sweating, as a result of transpiration, can help the plant to remove its inner heat, just as humans sweat to maintain their inner body temperature.  

As the water vapors are evaporated to outside air, making the outside air more moist or humid, heat is also reduced from the surrounding air. 

This provides plants with cool or more humid environments. 

Sweating, as a result of guttation, can help the plants to reduce salt stress or remove any excess minerals in the form of droplets. 

Hence, sweating can be good for plants’ overall growth and health. However, too much sweating can lead the leaf to lose its turgidity and lead it to wilt. 

How to Increase Humidity around Indoor Plants

On average tropical plants are subjected to a humidity of 88% in their natural environments, whereas the average houseplant will require a humidity that ranges somewhere between 30% and 40%. 

Misting increases the humidity around the plant. Although some argue that this is for a short period of time. The overall effect of humidity around a plant is to allow water to be absorbed by the plant.

Additionally indoor humidity can be affected by other factors such as seasonal conditions, wind, and appliances such as air conditions, radiators and fans.

What does humidity actually mean according to the National geographic encyclopedia

Humidity is the amount of water vapor in the air. If there is a lot of water vapor in the air, the humidity will be high. The higher the humidity, the wetter it feels outside.

Humidity is usually explained as relative humidity. Relative humidity is the amount of water vapor actually in the air, expressed as a percentage (%) of the maximum amount of water vapor the air can hold at the same temperature.

It’s not practical to mimic the full tropical conditions for plants as such high humidity can cause mold and fungus growth within our homes which can cause health problems.

However, we can temporarily increase the humidity around the plant by misting or using a humidifier.

Also see out article on how to correctly mist plants to get a better idea on the benefits of misting plants.

The Geniani portable humidifier from amazon provides the ideal environmental humidity for healthy plant growth. You can find it by clicking here.

geniani portable humidifier

JayLea

JayLea has a passion for plants and has been gardening since 2015. He has valuable knowledge about gardening and houseplant care and can answer everyday practical questions that every plant owner has.

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