Have you ever noticed the appearance of water droplets on your plants leaves? This is a phenomenon called guttation or transpiration. But how do we tell the difference? And why does it matter which method of water release the plants is using? As a scientist I enjoy using my formal education to help dissect the reasons why our houseplants and gardens do certain things. In this blog post we will look at why plants release water via guttation and transpiration. As well as determine the differences between the two and why it matters.
If you are new to this blog my name is Ashley and I am a soil scientist. I am located in a Canadian Zone 3 and a USDA Zone 4. I write articles, make YouTube videos, Instagram & Facebook posts all designed for Canadians and Cold Climate gardeners using science-based methods. If you are looking for anything specific be sure to let me know in the comments down below.
Why do water droplets form on leaves?
Water droplets forming on leaves is caused by moisture that much I obvious. But it is the source of moisture that determines if the leaf water droplets are harmful or a normal response. The dew we see on leaves in the morning hours is a normal occurrence due to changes in the ambient moisture.
The amount of water release from the plant is dependent on a few factors:
- Relative humidity
- Wind and air movement
- Soil-moisture availability
- Type of plant
Temperature: The rate of transpiration increases as the outside temperature increases. This is why during the summer months both indoor and outdoor plants require more water. As the temperature increases the plants needs to sweat in order to cool down. This sweating comes in the forms of water that is released through the stomata of the plant.
Relative humidity: As the humidity around the plant rises the rate of transpiration decreases. This is because the air is fully saturated and is unable to take on more water. This is when things such as dew being to form on the plant leaves.
Wind and air movement: This will cause higher levels of water loss because the likelihood of dry air or drying effects.
Soil-moisture availability: When the soil moisture is too low something called senesce will begin to take place. This is a fancy word for premature aging which may results in yellowing leaves or leaf loss all together. This will result in less transpiration in hopes of conserving water in the plant. On the flip side an excess of water will cause water droplets to form as well (we will get into this a bit later).
Plant Type: The type of plant will also affect how this process happens. For example, a succulent is less likely to give up water via transpiration vs. a thinner leafed plant such as a calathea.
Why does transpiration happen?
Transpiration in plants is mostly invisible. It is unlikely that you will see a form of water on a plant due to a transpiration process. Despite this transpiration is happening all the time and in relatively high quantities. It can account for up to 95% of all water loss in a plant.
Transpiration is a normal mechanism the plant uses to transport nutrients and even help cool the plant down in times of high heat. This entire process takes place with the use of stomata and guard cells. The number of stomata is based on the type of plant and its native environment.
How to Identify Transpiration?
It is unlikely you will ever physically see the process of transpiration taking place without some intervention. However, you can try an at home experiment where you tie a bag to your plant and see how much moisture is produced within a certain time frame. This will give you an idea of how much water the plant uses in a one-hour period for example.
Why does guttation happen?
Guttation is a much difference phenomenon when compared to transpiration. Guttation does not happen via stomata; it actually takes place using a special part called a hydathodes. Hydathodes act like valves in the plant allowing for excess water to be released. This release process generally happens during the night when the stomata are less active, but water pressure is still building up inside the plant.
Guttation is a result of too much soil moisture and therefore a sign of over watering. When our soil is fully saturated the plant is unable to export excess water back into the soil system. This is because the soil pressures are too high. Therefore, the next easiest way out is via the hydathode. This is the plants attempt at reducing the soil moisture content in hopes of prevention root rot.
Because the water droplets forming on the leaves are cause by pressure build up the plant has to fight against gravity. The force of gravity is increasing the taller the plant gets. This is why it is uncommon to see guttation in a plant over 3 feet in height.
What is in the water droplets found on leaves?
The process of guttation is caused by the hydathodes in the plant. These hydathodes are directly attached to the veins of the plants. Meaning they are directly tapped into the food source the plant needs to survive. When the water forms on the leaf it will consist of whatever the plant currently has for food in the xylem. This can include amino acids, salts, & sugars.
How to Identify Guttation?
Guttation is the droplets of water you find on the points of a leaf.
Is Guttation Bad?
Guttation is a sign your soil moisture content is too high. If you watered the plant in the last 24 hrs common sense would dictate that the plant is simply being dramatic. However, if the plant is still forming water droplets for days afterwards it maybe time to consider reducing the amount of water the soil is holding.
There are a few tricks to this, and I encourage you check out my article or video about it.
Its official you now know what the water droplets on plant leaves are. You can not decide if its time to act or simply leave things alone until the plant is able to regulate. Let me know if you have experience guttation.