Do You Keep Grow Lights on All the Time?

Views: 11     Author: Site Editor     Publish Time: 2022-09-05      Origin: Site

Modern agricultural technology has enabled gardeners to grow plants indoors using grow lights. Although plants normally do better in natural light, some thrive under artificial light. This is beneficial when you have limited outdoor space or prefer indoor growing techniques, i.e., hydroponics. Most gardeners have adopted in-house growing techniques, and if you are among them, you might wonder if it's always possible to leave grow lights on.

So, is it okay to keep growing lights on all the time? No, it's not advisable to always leave grow lights on. Plants require a defined light and dark cycle to grow appropriately. Some scientists believe that plants rest when in time of dark periods and likely use that time to distribute nutrients into their extremities. Apart from the expenses of keeping up with the electricity bill, some plants don't fare well with over-exposure to light.  Grow lights can also produce heat which might harm the plants.

Grow lights

There are various factors to consider when choosing to grow lights and indoor planting like:

  • What kind of plants are you cultivating

  • The development stage of the plant

  • What kind of lighting are you employing

  • How long do light and dark last

Let's take a deeper dive into why you should not leave growing lights on all the time.

Why you should not leave growing lights on all the time

The major reason why you shouldn't leave growing lights on all the time is that most plants are sensitive to the level of darkness and light they receive per day (day length). Day length is crucial as it informs plants which season it is, allowing them to know when it's time to develop flowers.

A perfect example is during short days ( approximately 9 hours), plants understand that it's winter, which is not the best time to flower. Also, some types of growing lights, especially high-intensity and incandescent lights, can produce excessive heat. It will leave your plants hot or dry if left on for long periods.

How long should you leave grow lights on

Most plants require a minimum of 8 hours of daylight each day. This corresponds to grow lights providing a minimum of 8hrs of artificial light daily. Keep in mind the crop and its stage of growth determine the precise duration of light exposure. To begin flowering, short-day plants require just under 12 hours of daylight (and over 12 hours of the night).

Plants can be grouped into three different categories, depending on their sensitivity toward light and day length:

  • Neutral length plants: This type of plant don't rely on daylight length to flower, for example, apples, tomatoes, cucumbers, some type of onions, and corn.

  • Short day length: These plants require less than 12 hours of light. Sweet potatoes, raspberries, blueberries, and other onions are great examples.

  • Long day length: For this type of plant to flower, they require over 12 hours of sunlight each day. Carrots, spinach, and lettuce are a few examples of long-day light plants.

By now, it should be evident that leaving growing lights on all the time is not a good idea since it might confuse your crops from knowing which season it is. Plants that use artificial growing lights require more exposure than plants growing under natural light.

The reason is: that it's challenging to replicate the same intensity light ratio of sunlight. However, you can employ high-intensity lights if your plants require extra light. Another option is to reduce the distance between the light and your plants.

Types of grow lights to employ

If you are in the market for growing lights, you have four options to choose from:

  • Incandescent: This type of artificial light most individuals are accustomed to is the incandescent light bulb. They produce large quantities of red light but tiny blue. This indicates that they're an unbalanced option for indoor plant growth. They generate a great deal of heat; regular incandescent bulbs are less energy efficient than the      alternative growing lights.

  • Fluorescent: Fluorescent light bulbs are excellent plant growing lights since they typically emit red and blue light. Additionally, they generate a lot less heat compared to incandescent light bulbs.

  • High-intensity discharge: High-intensity discharge lighting is built on halides or sodium gas. In greenhouses, these bulbs are frequently used.

  • LEDs: Light Emitting Diodes growing light bulbs produce relatively little heat. They last much longer and use little energy. LEDs can also be modified to create the required light wavelengths. They might be a bit expensive, but you can cut off the cost from low cost and maintenance.


Grow lights are a modern marvel that opens the agricultural world to newer possibilities. To sweeten the pot, grow lights are easy to use and maintain; however, a few things should be monitored, starting with the duration of light exposure. By now, it's evident that you should not always leave growing lights on as it might harm the plant or affect its development. Hopefully, this article will guide you down the right path.