Do Porch Lights Affect Plants? Here’s How

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Plants need light to grow among other vital inputs such as nutrients, soil, and water. Porch lights can alter a plant’s normal growth pattern by exposing the plant to more light than it should be receiving.

Porch and outdoor lights will affect plants by exposing them to an unnatural quantity of light. Increased lighting periods cause plants to produce growth hormones as a natural response. These hormones can affect the rate and direction in which plants grow, as well as their ability to produce flowers and healthy fruits.

Porch lights are a great way to keep your house looking nice and welcoming. However, it’s important to know that porch lights do have an impact on plants. Plants have many responses when it comes to light. These responses are dependent on the plant’s exposure to light. 

In this article, we are going to discuss all the effects that artificial and outdoor lights have on the growth and development of plants around the home.

Factors that Additional Light Affect in Plants

It Offsets Photoperiodism

The term photoperiodism is derived from two words: “photo†meaning light, and “period†meaning period.

The plant growth regulators are chemicals and physical factors that change the way plants grow. They affect the growth of both the roots and the shoots of the plant.

Photoperiodism is a process in which a plant responds to the duration of light or dark. It is a kind of biological clock. 

The duration of light and darkness affects the growth, development, and flowering of plants. 

During photoperiodism, plants also respond to seasonal changes in the length of light or dark. 

For example, during summer, days are longer than nights which entice plants to flower and fruit, which is why most plants produce fruits during this period of the year.

Disrupts Flowering

The flowering of plants is very sensitive to light-dark conditions.

Plants that flower depend on cues from their environment to determine when to produce flowers. 

Too much light can lead to an extension of the vegetative stage, but generally, too little light will prevent flowering.

An international team of researchers has found that the protein, called cryptochrome 3, controls the circadian rhythm of plants and regulates their flowering time. 

A study done by Max Planck Institute shows how the protein is activated by light and switches on the genetic program which leads to flowering.

Promotes Phototropism

Phototropism is the growth of an organism in response to a light stimulus.

During extended lighting periods, for instance, when the porch light is kept on all night it can trick the plant into thinking that it’s receiving sunlight from the direction that the light is coming from.

This causes the plant to produce more Gibberellin.

Gibberellin, a growth hormone, is increased and increases stem growth. Gibberellin increases auxins in the tip of the shoots and roots which promotes this growth. 

More light = More Gibberellin = More Growth

As a result, it increases legginess in plants as it promotes extra elongated growth towards the light. 

What you will notice is that the plant will start turning and growing towards the light and in its efforts in doing so it may start developing unnatural features such as the aforementioned legginess.

This symptom is more predominant in vined plants like monsteras and tomato plants.

If you would like to know more about how legginess affects plants you can see our detailed article here.

Additionally, our article on why do plants grow sideways will give a more detailed account of why plants lean and bend, and Using moss poles on houseplants will give you a cost-effective fix for when plant gets leggy.

Either Promotes or Stunts Growth 

Studies have found that blue light promotes the growth in plants as it causes the plant to produce more growth hormone. 

Therefore the amount of blue light a plant is subjected to will affect if it grows or becomes stunted.

Many of the lights that we use today produce a great deal of blue light such as energy-efficient LEDs.

LEDs are a great way to save energy if we are to use them in porch lighting or even for pathways and street lights.

Some of the brighter LED bulbs emit light in the 1000K to the 5000K range which can mimic close to daylight conditions.

Here are some light ranges and how they relate to light color temperature –

Color of light	Color intensity	Classification
Soft White	(2700K – 3000K)	Also known as Warm Light
Bright White/Cool White	(3500K – 4100K)	Also known as Natural Light
Daylight	(5000K – 6500K)	Also known as Cold Light

The spectrum of blue light increases as the color intensity increases.

The blue light in these spectrums can promote growth in plants if the light source emits white or cold light. However, if the light is of warmer nature, it will emit a lesser amount of blue light which can reduce the growth in plants.

Reduces Fruit Production 

As we have explained above, light can disrupt flowering in plants.

The ripple effect of lack of flowering extends to fewer insects as their food supply diminishes. 

Insects such as bees and wasps will start looking elsewhere for their food as the plant produces little or no flowers. As a result, the plant will also be affected as the pollination rate will reduce when there are little or no more insects around to carry out the process. 

Plants that can be affected by this are tomatoes, eggplants, ladyfingers, cucumbers, and bell peppers.

Produces Mutations

One simple example is a garden full of corn that I planted a couple of years ago. It was exposed to a street light at night as well as normal sunlight during the day. 

To compare, I also planted another garden of corn (in another location) at the same time which was not exposed to any external light.

The street light was definitely not as strong as the sunlight but it did have an effect on the way the plants grew and produced corn.

Here were the differences I found in both crops –

Corn plants that were exposed to the street light were
Taller than the ones in the other location.
The plants had sometimes split on the barks.
The corn that was produced was larger and sometimes had two in one.
The kernels were sparsely populated in the corn.

Distance of the Light and the Effect on Plants

The effects of light on plant growth and development can be affected by the intensity of light because there is an inverse relationship between distance and light intensity – as the distance increases, light intensity decreases. 

As the distance away from a light source increases, photons of light become spread over a wider area.

Therefore, the distance from the light source will have a direct effect on your plant.

Let’s take a 60 watt light source for example. If the light is located at 10 ft it will have a far greater effect on the plant than if it were situated 20 or 30 ft away.

Although it might not seem as far, 20 feet away from a 100 Watt bulb can make a big difference.

Light Sensitivity in Plants

Plants use light to create the food they need by absorbing light in the process of photosynthesis and lighting companies have used this fact to create lights that can provide the right conditions to maximize the process. 

[But there is something that they don’t tell you] Read on!

From studies done on how plants use lights for photosynthesis, it was shown that blue and red lights have the greatest effect on photosynthesis. 

In the experiment, a similar type of light was used for the same type of plant.

The light was separated into different spectrums of wavelengths meaning that the different plants of the same type were exposed to the different colors of the spectrum.

The plants that were exposed to the blue and red light independently showed to have photosynthesized far greater than the plants that were not.

For this reason, many companies have capitalized and have created lights that mimic this experiment to create the perfect spectrum of light that maximizes photosynthesis and hence greater plant growth.

Lights are then marketed based on this experiment to promote sales.

The catch: 

There is a reason that plants do well in full sunlight compared to if they are exposed to artificial lighting. 

With sunlight, you have to do little to ensure that a plant grows well. 

Just provide good soil and some fertilizer. However, with grow lights, you have to continually be tweaking the conditions to ensure proper plant growth.

This is because sunlight exposes the plant to the full spectrum of light that the entire plant utilizes for growth, not just blue or red light. A plant will use all lights in the spectrum to help promote biological processes which ensure their all-round growth.

Will Lights Around the Home Affect Plants?

Lights around the home can affect plants based on their intensity, duration, and distance.

LEDs, incandescent, and fluorescent lights emit light in their full-spectrum and will have an effect on a plant’s growth and development.

The greater the intensity and duration of light, the greater the effect.

Therefore a 60-watt bulb can have a greater effect if it was 10 ft away than if it was 20 feet away.

That same 60 watts of bulb will have a greater effect if it was to be left on an entire night than if it were to be intermittently turned on and off through a motion sensor.

The same goes for LED Solar lights in the lawn and pathways.

Higher wattage lights will have an increased intensity and the effect on plants is much greater than lights with a lower wattage.

Here are some common lights around the home and the effects they can have on your plant’s development.

Lighting Type	Duration	Effect on plants
Street Lights	Continuous	Will cause disruption in flowering and growth pattern
Flood lights	Intermittent/ sometimes continuous	Will cause disruption in flowering and growth pattern
Headlights from a car	Intermittent	Little or no effect on the plant
Security lights	Intermittent	Can cause disruption in flowering based on intensity and duration
Flash lights	Intermittent	Little or no effect on the plant
Night lights (for indoor use)	Continuous	If plants are close it can cause disruption in growth
Solar lights	Continuous	If plants are close it can cause disruption in growth

Homeowners that have raised bed gardens that are exposed to the street light or other forms of light would notice how these artificial lights affect their plants.

Tomato is one of the plants that will show these effects to a greater extent since it can grow very tall in response to increased light exposure. 

Flowering patterns in tomato plants will also change followed by fruit mutation.

How Natural Light is Different from Artificial Lights

Natural Light – Sunlight

Natural light (sunlight) provides light in the full spectrum for a fixed period of time during the 24-hour cycle. 

The daylight cycle is affected by the time of year where the tilt of the earth with respect to the sun produces the different seasons which we are accustomed to.

Therefore a plant will get less sunlight during the day at the beginning of spring than in the middle of summer (July-August months).

This change in light duration causes plants to produce fruits during longer periods of light and also causes them to go dormant in shorter periods such as winter.

Plants become accustomed to this type of seasonality and lighting and adjust their circadian cycle based on the seasons.

Artificial Lights – Outdoor Lighting

Outdoor lighting can produce similar lighting conditions to that of natural sunlight based on the type of lighting used. 

Solar lights are widely used to light pathways at night which primarily have LED bulbs built into them.

Although LEDs are very popular and also energy-saving, the majority of households still use incandescent lights. This is also true for street lights which light our roadways. 

The driving factor is cost as they are readily available and are cheap.

Incandescent light can mimic sunlight on a smaller scale. This means that it can have the same effect as sunlight on plants but to a lesser extent.

With this being said, artificial lights can be put on and taken off with the flick of a switch that is far from natural. 

Seasonality does affect how long outdoor lights are on, because shorter days would mean longer nights which equates to longer lighting times for the artificial light.

These changes in lighting duration will affect plants since it affects their circadian cycle when they are exposed to the source.

Will the Light from the Neighbor House Affect My plants?

Lights from neighboring houses can affect your plants based on the intensity, distance, and duration of the light that the plants are exposed to.

Here are the guiding rules –

Greater the intensity = Greater the effect on your plants

Greater the duration = Greater the effect on your plants

Lesser the distance = Greater the effect on your plants

Now, this is a problem many of us may face as we cannot control what our neighbors do with their lighting system. 

Bright security and floodlights from nearby sources can affect how your plant grows and functions as discussed above.

Here’s what you should NOT do!

Do not shoot out your neighbors light however compelling it may seem. You may land yourself in trouble. Not to mention if you miss your shot. Just don’t do it!

Here’s what you can do 

Have a kind chat and let your neighbors know that their lights are affecting your plants and if they can kindly switch them off at night.

Mention how much money it may save by not having the light on all the time. That might help.

It’s worth a try.

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