Do Plants Grow at Night? [Photosynthesis vs Respiration]

Plants do grow at night which contradicts the common myth that plants only grow in sunlight. In fact, some plants even grow faster at night than during the day.

To understand how a plant grows, you need to understand the processes of photosynthesis and respiration. These are two separate processes but both are necessary for plant growth.

Read on to learn more about photosynthesis, respiration and how a plant grows at night or during the day.

Photosynthesis vs Respiration

Most people have learned in biology class that plants use photosynthesis to produce their own food. However, consuming the energy of this food is done through respiration.

Photosynthesis is a process whereby plants absorb sunlight to convert water and carbon dioxide into glucose. This glucose is the source of energy for plants, just like with humans.

Since photosynthesis cannot occur without sunlight, plants only use this process during the daytime when there is light. That means there is no photosynthesis at night.

Respiration is a process whereby plants consume their self-made glucose for energy. This energy is what the plant uses to grow.

Plants have circadian rhythms so they can distinguish between daytime and nighttime. During the day, the plant both photosynthesizes and respires but at night photosynthesis stops and the plant only respires.

Plant Growth During the Day and at Night

Plants grow both at both daytime and nighttime. However, they grow differently.

If you have looked up plant care, you will have come across the advice to place plants near windows for more sunlight. If you follow this advice, you might notice that plants tend to grow towards the sun.

During the day, when plants are absorbing sunlight their growth is more horizontal, in the direction of the sunlight. Plants that enjoy sunlight also tend to grow larger leaves – larger leaves means more chloroplasts which means more sunlight absorption.

However, this does not mean that photosynthesis is a growing process. Plants only grow during respiration but sunlight can affect in which direction plants grow.

At night, plants tend to grow more vertically because there is no sun to direct them. Depending on the type of plant, the growth in height may be more noticeable.

Some plants grow faster at night than during the day.

Some plants grow faster at night because the photosynthesis process has stopped, allowing the plant to focus on respiration. However, the difference in rate of growth depends on the type of plant and in many plants there is no significant difference.

Frequently Asked Questions:

What Do Plants Do in the Dark?

When there is no sunlight, plants continue to respire. During respiration, plants consume the stored energy they created during photosynthesis and use that energy to grow.

Can Plants Be Watered at Night?

Whether it is okay to water a plant at night depends on the environment. In many cases, it is not recommended to water plants at night because it could potentially cause root rot.

At night, water evaporates slower because of the cooler temperatures and lack of sunlight. This means that pot soil stays saturated for longer.

At the same time, plants require less water at night because they don’t photosynthesize in the dark. Less water absorption and longer saturated soil are a major cause of root rot which is why most houseplants should not be watered at night.

The exception is for outdoor plants in very hot areas. In tropical weather, it is better to water outdoor plants nearer to dawn and dusk because high temperatures could cause the water to evaporate before the plant is able to absorb it.

What Plant Can Live in the Dark?

Certain plants can survive in dark rooms because they need very little sunlight. Examples of these types of plants include:

Summary

The short answer to ‘do plants grow at night?’ is: yes, they do. However, there are many misconceptions about how plants grow.

Many people think plants grow during photosynthesis but this is not true. This is where the wrong idea of plants only growing during the day comes from.

Plants grow during respiration and plants respires continuously, both during the day and at night. So, even though photosynthesis stops when the sun goes down, respiration does not.

Since plants still respire at night, plants also continue to grow at night. Plants seem to grow faster at night but although this is true for some plants, most plants grow at very similar rates during the day and night.