The BASICS: How to Use Grow Lights for Indoor Plants! | 🌳

What would you do if you want to set up an indoor garden, but the lighting environment inside your house is inconducive? One of the options you would probably consider is investing in grow lights. These gardening accessories provide full-spectrum light enabling plant growth in areas that would otherwise be inhospitable for plants due to limited lighting. Grow lights also come in handy during winter when there is barely any direct sunlight to aid plant growth. This article will go over the different types of grow lights, how to use them, and how to choose the best.

What is a Grow Light?

A grow light is an artificial light that allows you to cultivate a wide range of plants in conditions with insufficient natural sunlight. This could be in poorly lit rooms or during winter. A grow light is designed to mimic natural light and stimulate photosynthesis in plants that don’t receive direct sunlight.

Additionally, grow lights provide the necessary spectrum for plants to flourish. Simply put, it can let you grow sumptuous tomatoes smack in the middle of winter.

There are numerous plant types you can grow indoors using grow lights, so the options are only limited by the space you have and the lights you are willing to get. Like numerous other gardening tools and accessories, grow lights come in several sizes, shapes, features, and materials. Most of these lights are also energy-efficient, making them viable indoor gardening tools.

How to Use a Grow Light

Here is a brief look at some useful tips to keep in mind when it comes to using a grow light.

Lighting Plan for Transplants

Once seedlings have sprouted, they require full-spectrum light to flourish. This means that the young plants thrive when exposed to both blue and red waves. Specially-designed fluorescent and LED lights work perfectly in this stage, but regular tube bulbs will also work. It is important to ensure that the bulb is at least six inches away from the plant’s tender leaves. If you have an adjustable light, make sure to raise it as the plants’ height changes.

Lighting Plan for Flowering Plants

Flowering plants require a lot of red wavelength light than sprouting ones. This light enhances flowering and fruit formation. Once your indoor plants get to this stage, ensure you have LED bulbs designed for flowering plants. Such bulbs are typically labeled ‘grow lights’ and have more red waves than conventional bulbs. Additionally, some manufacturers have high-output bulbs that are also ideal for flowering plants. However, keep in mind that these high-intensity bulbs are best suited for plants native to full-sun climates, such as rosemary, citrus, and cactus. It is advisable to place the light at least one foot away from the plant’s leaves.

How Much Light Do You Need?

The exact amount of light you need varies from one plant type to another, as well as space you need to illuminate. However, as a general rule, you require about 20 to 40 watts for every square foot of space. To start with, divide your bulb’s wattage by 20 and then by 40. For example, if you have an 800-watt bulb, divide it by 20 to get 40 and 40 to get 20. These calculations imply that your bulb can sufficiently illuminate an area measuring 20 to 40 square feet. When getting bulbs, it is important to only fix them into a system that can handle the power rating. For example, you should not use a 500-watt bulb in a system rated 200 watts.

You can always reduce or increase the output intensity by moving the plants or growing light closer or farther from each other.

Tips and Reminders for Using Grow Lights

Using grow lights for your indoor gardening project requires quite some input from your inside. Here is a look at some basic tips and guidelines to keep in mind.

Use a Timer

Plants typically don’t require continued exposure to light and we will discuss this bit a little later in this guide. Most plants require several hours of darkness. To do this, you need to shut off the light if you have one without a timer. However, doing this can become quite tedious, especially if you are frequently out of the house.

The easiest option is to get a grow light with an auto-timing function. This feature lets the light switch on and off in line with some preset conditions.

Adjust the Light Height Accordingly

Most grow lights come with some form of adjustment. This might include an overhead cable, flexible stand, or any other mechanism. Once your plants have sprouted, it is easy to forget to adjust the grow light as the plants grow taller. Failing to do this exposes the plants to a higher light intensity than they may handle. You should, therefore, adjust the light upwards as the foliage gets closer. If necessary, move the entire light farther from the plant.

Have a Rotation Schedule

For most grow lights, the light output from the middle of the bulb is more intense than that from the outer areas. To balance this out, you need to rotate the plants illuminated by the middle section and periodically place them under areas lit by the bulb’s outer sections. Doing this will enhance uniform foliage growth in the plant.

Check the Soil Water Level Regularly

When using grow lights, particularly the high-intensity ones, the potting soil may dry up quite quickly. This accelerated drying comes from the heat emitted by the bulbs. This makes it essential to check the soil water level periodically so that your plant’s roots are not affected. It is also worth noting that the soil might dry even faster in winter due to the heat coming from your house’s warming system.

Watch the Temperatures

While most grow lights do not emit significant heat, some variants, such as those made of metal halides, can get quite warm. This heat can significantly affect the room’s ambient temperature, which in turn affects your plants. If the ambient temperature rises too much, it may create a less-than-ideal environment, especially for young plants.


The maintenance you need to carry out on your grow lights largely depends on the type of bulbs. LEDs, for example, require little to no maintenance. Other lights might require regular inspection and dusting to enhance durability. If the light manufacturer has a suggested maintenance schedule for the bulb, follow it to the letter.

Getting the Right Light for Indoor Seed Starting

If you head over to any online shop and browse growing lights, you will quickly realize there are almost countless options available. While having several options to choose from is a good thing, numerous choices can easily overwhelm you. Here are some of the factors to keep in mind when selecting a grow light.

Plant Type

The crops you intend to farm under the grow light will determine the type of bulb to get. For example, if you intend to farm microgreens, the coverage, spectrum, and intensity requirements will vary significantly from those of a gardener intending to farm flowers or herbs. It is important to research the different lighting requirements for various plant types.


Like any other gardening accessory, lighting tool prices vary from one manufacturer to another. Sometimes, the price difference reflects the underlying differences in quality but not always. It is important to consider your entire budget before setting up your indoor garden. For example, if you can only afford five grow lights, you need to set up a garden that five or fewer bulbs can sufficiently illuminate.

Bulb types

Grow light bulbs fall into four major categories; fluorescent, LED, incandescent, and high-intensity discharge bulbs. Each class of bulbs has its pros and cons. Fluorescent bulbs, for example, quite affordable but not very durable or efficient. On the other hand, LEDs have excellent spectrum coverage, are highly efficient, and emit almost no heat. However, they tend to be pricier than any other grow lights.

Light Spectrum

Light waves have different colors, often referred to as a spectrum. Most plants require the red and blue ends of the light spectrum with a little bit of green and yellow included. Blue light is essential for plants in the vegetative stages and helps in the development of roots and leaves. Red light is essential for flowering flowers and those in fruit development. In terms of the light spectrum, grow lights come in two distinct types; full-spectrum and targeted spectrum. The former imitates sunlight and provides light waves covering all the colors. The latter emits a specific color, say red or blue, and are better suited for specific growth stages.

Light Intensity

This basically refers to the amount of light that actually falls on the plant leaves. It is important to consider the bulb’s output since it will determine how much light falls on each plant and how much space can be sufficiently covered. A high-intensity bulb can illuminate a wide area even when placed far from the plants. However, keep in mind that a high-intensity bulb will probably produce significant heat and can therefore harm plants if placed too close.


Before purchasing a grow light, it is important to ensure its mount comes with some form of height adjustment.

Having this feature allows you to adjust the light upwards as the plants grow taller. Additionally, you can get lights with some level of portability to allow relocation as plants grow wider. Most high-quality lights come with swivel stands adjustable for height, tilt angle, and direction.

Types of Grow Lights

Here is a look at some of the most common types of grow lights.

Incandescent Bulbs

Incandescent lights are ideal for plants with low light requirements. Keep in mind that incandescent bulbs can get quite hot and need to be placed at least two feet from plant foliage. If your garden has dracaenas, ferns, or vines, you should definitely consider an incandescent light. The total energy output from this bulb is only 10% light and 90% heat. In terms of efficiency, these bulbs might not be your best option, particularly due to the considerable heat output. You may want to avoid using such a light on light-loving plants such as succulent and tropical plants.

Fluorescent Lights

Arguably the most affordable grow lights out there. Newer fluorescent lights have full-spectrum light, making them ideal for virtually any plant type and growth stage. Keep in mind that older models have limited spectrum output and are ill-suited for the vegetative and germination phases of plant growth.

Compared to incandescent light, fluorescent lights produce less heat and are, therefore, more efficient. However, they still lag behind LEDs on this front.

High Intensity Discharge Lights

Commonly referred to as HID lights, these bulbs are typically made from metal halides and high-pressure sodium.

Unlike the highly affordable fluorescent lights, HIDs can be quite expensive to purchase and operate. On the flip side, the high-intensity blue light emitted by metal halide HIDs is excellent for most plants’ vegetative and germination stages. High-Pressure Sodium lights have an orange-red hue, excellent for the flowering and fruit production stages but not ideal for the vegetative stage.

LED (light emitting diode) Lights

LEDs are the new kid on the block when it comes to growing lights and, unsurprisingly, among the most popular.

LEDs emit almost no heat and require very little power to operate. These diodes can be programmed to mimic the sun’s 5700K color temperature. Additionally, LEDs provide full-spectrum light, making them ideal for all plant growth stages. Compared to fluorescent lights, LEDs are still quite pricey, although the prices are gradually dropping.

Keep in mind that while grow lights are quite good at what they do, they are still not a perfect replacement for sunlight. However, choose the light that best suits your preferences and budget, position it correctly, and you will have excellent results.

How Long Should the Grow Light Be Left On

Now that you have purchased your full spectrum grow light, how long should you keep it on? The exposure duration [1] is known as the photoperiod and varies from one plant type to another. Typically, most plants require 16-18 hours of light on each 24-hour cycle. More exposure to light might not have any additional benefits to the plant. While light has immense benefits, most plants also require some darkness to flower and form fruits properly.

It is important to consult your local gardening center if you are unsure about the ideal photoperiod for the plants in your garden. Plants are divided into three categories depending on their behavior when it comes to light. Here is a brief look.

  • Day-neutral plants: These plants require 8-12 hours of light each day throughout the year. Prime examples of day-neutrals include African violets, coleus, and geraniums.
  • Long-day plants: These plants have the highest light requirements ranging from 14-18 hours of light each day. When placed in an inadequately lit environment, long-day plants become leggy and turn pale. Examples of long-day plants include garden flowers and vegetable seedlings.
  • Short-day plants: Plants in this category thrive with less than 12 hours of light per day. Short-day plants often require several days of short-day light before they can form buds and flowers. Examples include begonias, azaleas, kalanchoes, and chrysanthemums.

Once you have established your plants’ light requirements, you will need to set your automatic timer accordingly. If you do not have one of those, feel free to create a schedule to switch the lights on and off manually.

What Color Light Is Best for the Plant Growth

Most full-spectrum grow lights are designed to emit every wavelength of light, including those not visible to the human eye (such as UVB and UVA). However, the light that comes from these lights is more focused on useful waves such as red and blue. Focusing on these lights enhances growth, [2] flowering, and fruit production. Typically, plants use the warmer, shorter wavelengths found in blue light to grow and mature. They then utilize the cooler, longer wavelengths found in orange and red light to flower and produce fruit.

Here is a breakdown of the various light colors [3] and their uses/effects on plant growth.

  • Blue light: Ideal for the foliage growth and vegetative stages.
  • Orange/red light: Excellent for flowering and fruit production stages.
  • Green light: Has little to no effect on plant growth. Chloroplasts found in plant leaves often reflect off green light.
  • Ultraviolet light: Plants grow better when exposed to less ultraviolet light.
  • Violet light: Enhances the aroma, color, and taste of fruits.
  • Yellow light: Yellow light results in slower plant growth compared to blue or red light.
  • Infrared light: Enhances the conversion of phytochrome, reducing the time it takes for the plant to enter a night-time state. Consequently, this results in better plant yields.


Grow lights are undoubtedly some of the most important components of indoor gardening. These lights expand a farmer’s possibilities, allowing crop production in less-than-ideal lighting conditions. By following this guide, you can easily choose the perfect light for your indoor plants.


We will be happy to see your thoughts

Leave a reply

1 × 5 =