How to Choose the Best Grow Lights for Your Indoor Plants

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Plants need energy to survive and light plays a big role in providing that energy. As part of the photosynthesis process, plants transform the sunlight they receive into chemical energy or food. But when it comes to growing plants indoors, providing enough sunlight can be tricky since our windows only provide a fraction of the light plants need. The best way to solve this problem is through the proper use of grow lights. This article will walk you through how to choose the best grow lights for your indoor plants based on what you’re growing and the space you have.

1. Decide If Your Plants Need Grow Lights

The first step to finding the best grow lights for your indoor garden is to figure out whether or not your plants need grow lights in the first place. Below are some examples of indoor plants that benefit from grow lights.

Common houseplants

Variety of green cactus in pots

Most houseplants do not require a grow light setup, unless you do not have windows that face south or east. These common low-light plants that thrive without grow lights include:

  • Orchids
  • Monsteras
  • Snake plants
  • Ferns
  • Philodendrons
  • Spider plants
  • Lucky bamboo
  • Some palms

However, many light-loving plants, like succulents, air plants, and cacti have become indoor staples, and they often need grow lights to thrive. Before you buy a houseplant, look up its light level requirements. If it likes full-sun, you will want a grow light. Some of the most common indoor plants that need grow lights include:

  • Kalanchoe
  • African violets
  • Aloe
  • Sedums
  • Rosularia
  • ZZ Plants
  • Aglaonema
  • Fiddle leaf figs
  • Bird of Paradise

Transplants

Veggies with LED grow light.

Transplants — whether they’re vegetables or flowers — benefit from grow lights. Many gardeners start their vegetables indoors before planting them in their outdoor vegetable gardens. Without ample light, vegetables like tomatoes and peppers become “leggy” as they stretch to find a better light source. Leggy plants do not transplant well because they’re too weak to support their own produce and they’re more vulnerable to disease.

The same is true for gardeners who start their flowers from seed indoors before transplanting them outdoors. To ensure they grow and remain healthy, you’ll want grow lights.

Plants winter indoors

Outdoor potted plants that need to winter indoors frequently require grow lights. Most of these plants are accustomed to sunlight and will suffer from the lack of light indoors.

2. Choose the Right Type of Grow Light for Your Plants

There are four main types of grow lights: high-intensity discharge, LED, fluorescent, and incandescent. To choose the right grow lights for your plants, it’s important to know the differences between them.

High-Intensity Discharge (HID)

Veggies under HID grow lights

HID lights are the most powerful and brightest grow lights on the market. They’re the top choice for commercial plant growers.

HID lights are composed of two diodes — one on each side of a glass tube. The tube is filled with gas, and when an electrical current is sparked, the electricity leaps from one side to the other, illuminating the gas to create light.

Metal Halide (MH) and High Pressure Sodium (HPS) bulbs are the most common bulbs for HID lights. MHs operate in the blue spectrum which is best for plant growth. HSPs operate in the yellow light spectrum, which is optimal for flowers and vegetables. To decide if HID lights are right for you, it’s best to consider their benefits and drawbacks.

Benefits of HID lightsDrawbacks of HID lights
Are the brightest grow lights available.Can become extremely hot and often require a cooling system for safety’s sake.
Nourish the entire plant, not just the top section.Require more frequent waterings due to evaporation from the light’s heat.
Have been around the longest, leading to better innovation.Are the least energy efficient option and cost more to operate.

LED

LED grow lights

LED grow lights are more popular among home gardeners. Unlike traditional light bulbs, LEDs are essentially just the diode without the bulbs. They offer dense energy emission and emit a greater spectrum of light wavelengths, which means growers can customize their LED light to emit a specific wavelength for their plants.

Benefits of LED lightsDrawbacks of LED lights
Great for hobbyists and home growers.Higher initial cost.
Extremely energy efficient.Their violet hue can distort plant color and mask damage.
Produce more wavelengths of light color.Large setups can be heavy due to built-in heat regulators.

Fluorescent

Fluorescent grow lights

Fluorescent grow lights are most often used on small-scale farms. These lights emit ultraviolet light that reacts with the phosphorus coating, making the light visible.

If you choose to use a fluorescent bulb as a grow light, purchase a high output bulb. The narrower the bulbs, the higher the output. T5s and compact fluorescent bulbs are ideal for plant growing. Fluorescent light is bluer than other choices, which works well for stem and foliage growth, but not for flowers or vegetables.

Benefits of fluorescent lightsDrawbacks of fluorescent lights
Can be purchased from common stores.Often very fragile.
Effective for simple plant growth.Only emit blue light.
Less energy expense than incandescent bulbs.Produce excess heat.

Incandescent bulbs

lightbulbs hanging over the top of a row of potted plants

Incandescent lights are normal household light bulbs. They are the least popular for growing plants indoors. They produce a lot of heat while only emitting a small amount of light energy. Often they have to be so close to the plant to be effective that they wind up burning the plant. They do work fine to provide shade-loving plants a little extra light, though.

Benefits of incandescent bulbsDrawbacks of incandescent bulbs
Easy to find and set up.Produce a lot of heat.
Provide extra light to shade-loving plants.Emit lesser amounts of light energy.
Frequently burn plants.

3. Determine Your Plants’ Wattage Needs

When sorting through the different grow light options, you’ll notice different amounts of wattage. If you choose to go with LEDs, the manufacturer will list a wattage equivalent.

To determine your indoor garden’s wattage needs:

  1. Measure the square footage of your growing area.
  2. Figure out your plants’ lighting needs:
    1. Full-sun plants = high light needs = 40 watts per square foot
    2. Partial-shade plants = moderate light needs = 35 watts per square foot
    3. Shade plants = low light needs = 25 to 30 watts per square foot
  3. Multiply your square footage by your plants’ wattage needs:

    Square footage of growing area x Plant’s wattage needs = Garden’s wattage needs

    Example: If you’re growing full-sun vegetables in a 2-foot by 2-foot growing area, you would multiply the length (2 feet) by depth (2 feet) to find your square footage, which equals 4 square feet. Next, you multiply your square footage (4 square feet) by the full-sun vegetable plants’ wattage needs per square foot (40 watts per square foot) to get 160 watts.

    2 ft x 2 ft = 4 sq ft
    4 sq ft x 40 watts = 160 watts

4. Place Lights at the Proper Distance

Deciding how close to hang or place grow lights to your plants is a balancing act. You want the lights close enough to prevent the light they emit from becoming too dispersed and less effective. Yet you do not want the heat from the grow lights so close that they burn your plants.

The easiest way to figure out the distance is by the type of light you’re using. Follow these guidelines to determine placement:

  • LED and fluorescent lights can be within 6 to 12 inches of the top of plants.
  • HID lights should be hung about 12 to 15 inches above plants.
  • Incandescent bulbs should never be within 24 inches of plants.

As your plants grow, remember to raise the height of the light. Adjusting their distance once per week is a good way to monitor plant growth and prevent damage caused by grow lights.

5. Choose a Light Color or Spectrum

plant grow light’s spectrum

To select your grow light’s spectrum, you want to choose based on your plant’s dominant feature: flowers, vegetables, or foliage. Here’s their corresponding light spectrums:

  • Flowers: Red light is best for flower production because it is the most efficient for photosynthesis which produces extra energy for flowering.
  • Vegetables: Vegetables also benefit most from red light because the efficiency of photosynthesis helps create excess energy that can be stored by the plant.
  • Foliage: Blue light is necessary for foliage growth. Blue light is also very efficient for photosynthesis but foliage also needs some exposure to red and green light.

When selecting a grow light, you’ll likely want a spectral mix of red and blue that leans more heavily toward your plants’ features.

You also want to be sure that your grow light has some green light, since green light is highly beneficial to plants. Green light penetrates below the top leaves, providing light for bottom leaves to photosynthesize.

Other Considerations for Choosing Grow Lights

Reflective elements

Reflection maximizes your grow lights’ effectiveness by redirecting light back, at a different angle. Aluminum foil and mylar are cost-effective ways to multiply your light. You can pin it up around the plants and place a layer beneath the pots.

Setup

The setup you create for your grow lights depends on your space and your gardening goals. The following are the most common setups for grow lights:

  • Modular: These systems are excellent for gardeners that are just starting out but want to expand, or only have a need for grow lights during the winter.
  • Permanent: Growing plants on shelves with permanent light fixtures is a wonderful option if you have dedicated room or space for your indoor plants. This can keep your indoor plants happy 365 days of the year. This is a great option for people who truly want an indoor veggie garden or have an ongoing need for grow lights.
  • Mobile: If you grow a limited number of plants throughout your home, you can use a lamp with a compact fluorescent bulb. Simply move it from spot to spot to keep each plant fed. This is by far the most attractive grow light option as well.

Hours of light per day

While our focus has primarily been on providing light to indoor plants, it’s important to note that plants need a certain amount of darkness. That’s because plants use dark hours as their designated respiration time.

Most full-sun plants thrive on 12 to 16 hours of light per day. Medium-sun (or partial sun) plants enjoy around 8 hours of light per day. You’ll need to develop a system for adhering to these light and dark requirements.

Many simple LED grow light setups come with easy-to-use timers you can set to set on or off reminders. Some come with a countdown timer to stay lit for a certain amount of time after you turn the light on. Others come with timers you can pre-set to automatically turn on and off at selected times of the day.

If you opt for a more low-tech setup, you can set a reminder on your phone. It can also be helpful if you turn your lights on and off at the same times daily.

Conclusion: Do Your Homework

Growing plants indoors isn’t difficult, but as with all other gardening endeavors, it takes research to do it well. Take your time and use this article to make a list of the grow light specifications your plants need before purchasing any setups and bulbs.