Indoor plants need light to thrive just as much as any other plant. Though greenhouses are designed to let in as much natural sunlight as possible, there may be times when your greenhouse-grown plants are not receiving enough light. For example, maybe the light is being blocked by trees, shelving units, or the foliage of other plants, or maybe the days are simply getting too short to provide your plants with sufficient natural light.
If you’re struggling with inadequate lighting in your greenhouse, you should consider supplementing with grow lights. The right amount of supplemental lighting not only enhances photosynthesis, but it speeds up germination and guarantees healthy blooms!
But with so many options available on the market, it can be a challenge to find the right grow lights for your greenhouse and unique growing needs. Factors such as illumination, cost, and light spectrum all figure into selecting the best greenhouse lights for your needs. Keep reading to learn everything you need to know to pick the right grow lights for your greenhouse, plus our recommendations for you!
Grow lights vs. regular lights
Plants can’t photosynthesize without light, which allows them to convert water, carbon dioxide, and minerals into oxygen and energy needed to grow and develop. While you might be tempted to install regular lights in your greenhouse to supplement natural light and save costs, it’s important to understand that not all light is created equal.
Essentially, the chlorophyll in plants is the most responsive to the red and blue wavelengths of light, or the 400-700 nm range of the visible light spectrum. Green light, roughly in the middle of this spectrum, is not as easily absorbed but penetrates deeper into leaf tissues.
Grow lights are designed to meet the light spectrum needs of plants for all stages of growth, making them the most efficient choice for the greenhouse grower. Regular lights, on the other hand, may not provide the right light wavelength for plants to photosynthesize. Additionally, incandescent light bulbs, besides being highly inefficient, can emit too much heat and burn leaves. And while the blue light of fluorescent bulbs makes them an attractive option, the intensity of light emitted is not enough for flowering or high-light-demanding plants. If you’re hoping to grow fruits and vegetables through the winter, grow lights are a must-have greenhouse accessory.
Different types of greenhouse grow lights
In order to pick the right type of lighting for your greenhouse, you’ll need to understand what you’re looking for. First, there are three different greenhouse lighting systems commonly referred to as grow lights:
T-5 fluorescent lights
T-5 fluorescent lights are full-spectrum light bulbs that are efficient and have a high light output. They use less energy than incandescent lights and can last up to 50,000 hours, making them the workhorses of commercial greenhouses. They are particularly good for starting seedlings and growing leafy greens.
High-Intensity Discharge (HID) lights
HID or High-Intensity Discharge bulbs can provide efficient lighting over large areas. However, they have to be installed at a distance as the heat output can cause leaf burn. There are two kinds of HID bulbs: high-pressure sodium and metal halide.
- High-pressure sodium (HPS) bulbs emit red light that’s best used to encourage flowering and budding.
- Metal halide bulbs emit blue light that stimulates bushy growth.
LED Lights
Light-emitting diodes, or LEDs, are no longer the new kid on the block. In many cases, they’ve superseded other types of grow lights. They offer a balance of performance, energy efficiency, and low cost. What sets LEDs apart is their ability to be tuned to specific light spectrums, catering precisely to the varying needs of plants through different growth stages. LEDs also give off less heat than other lights and are more energy efficient, with an average lifespan of 11 years.
Factors to consider when choosing greenhouse grow lights
Besides the type of light bulb, there are a number of other important aspects to consider when selecting a greenhouse light system. Greenhouse grow lights should be long-lasting, energy-efficient, and cover a wide area. Additionally, greenhouse grow lights should have the option to be used alone or daisy-chained together to easily and efficiently cover a wider area.
Are the grow lights waterproof?
It’s important that the grow lights you choose for your greenhouse are waterproof, as you’ll be watering your plants frequently and humidity can remain high in the greenhouse environment. Grow lights that aren’t properly sealed can malfunction when exposed to too much moisture, and that’s the last thing you’ll want to deal with.
Grow lights designed specifically for greenhouse use are usually waterproof or highly water-resistant, but it’s still important to check if a particular product is waterproof or at least able to withstand high moisture levels.
How much area do the grow lights cover?
Another important consideration is how much surface area the grow lights cover. Whether you’re trying to provide light to your entire greenhouse or multiple shelving units, you’ll want to calculate the total surface area so you can get the right number of lights. Watts are a good, albeit imperfect, indicator of how much surface area a grow light will cover: higher wattage generally indicates that a grow light can cover more space at a greater distance from the plant canopy.
However, LED lights operate more efficiently than traditional grow lights, so you can get the same amount of light for fewer watts. Often manufacturers will distinguish between displayed vs. actual wattage for this reason. For instance, a single LED grow light might use 25 actual watts, but give off light equivalent to a 50 W HPS grow light. Both lights will provide enough light for approximately 1 square foot, but the LED light will do so more efficiently.
What is the grow light’s range?
Grow lights with higher wattage are generally more powerful and emit more light, but we also know that LED’s are more efficient at lower wattage. That said, you can use the “displayed wattage” of an LED grow light to figure out a grow light’s range, or how far away you can place it from the plant canopy without sacrificing light intensity.
Here’s a general rule of thumb:
- 100 W = 8 -12 inches away
- 200- 399 W = 12- 20 inches away
- 400- 599 W= 20- 30 inches away
- 600+ W = 30+ inches away
For best results, make sure to monitor your plants at various distances. If a plant appears to be leggy or stretching towards the light, move the grow light closer. If you observe leaf burn or bleaching, move the grow light farther away.
Low-light vs. full-sun plants?
If things weren’t complicated enough, you’ll also need to consider the needs of individual plants when choosing and placing your greenhouse grow lights.
Low-light plants such as tropical houseplants or leafy greens don’t need as much direct light to thrive. You can either place grow lights farther from the plant canopy and/or reduce the amount of time a grow light is on during the day.
Sun-loving plants such as tomatoes, on the other hand, might need as much as 12-16 hours of bright light close to the canopy.
Group plants with similar light requirements together so you can adjust your grow lights accordingly. For example, raise grow lights farther away from the plant canopy for low-light plants, or closer for plants requiring full-sun conditions.
You can even set grow lights on a particular schedule using a timer such as this one.
Are different grow lights necessary for different plant stages?
Plants benefit from different light ratios at various points in their life cycle. For instance, seedlings perform best with more blue light, while plants need more red light when developing blooms and fruit.
Many greenhouse grow lights offer a balanced light spectrum that can meet the needs of all plant stages. That said, some grow lights can toggle between different modes (for example, red light vs. blue light) to enhance leafing or blooming as needed.
For most hobby greenhouse growers, it’s not necessary to buy and install different grow lights. If you want to switch between different light colors, simply choose a single grow light with those modes. For most purposes, however, a full-spectrum grow light supports healthy plant growth at all stages.
The best greenhouse grow lights
To help you pick the right grow light for your greenhouse, we’ve narrowed down our top choices in the following categories: germination, flowering, vegetation, and budget.
Best choice for seedlings: MARS HYDRO TS-1000 Led Grow Light
This square, 3ft x 3ft LED grow light is perfect for starting seeds. It boasts full spectrum light with high efficacy in the blue and red ranges, with blue light being more important for germination and early leaf development. The 120° refraction angle ensures wide coverage, but you can cover even more area by daisy-chaining multiple lights together.
Product features:
- 150 W
- PPFD: 343 umol/m2s@12
- Full light spectrum (730-740nm Red IR/3200-4200Knm/5200-6800Knm)
- Light-weight at 3.7 lbs
- Max coverage is 3ft x 3ft
- 120° refraction angle ensures good coverage
- You can daisy chain up to 60 lights together, great for a medium-sized greenhouse
- There is an adjustable 0-100% dimming feature
- Ideal height from canopy for germination: 12”
- 5-year product warranty
Best choice for healthy blooms: Illumitex Eclipse GEN2 LED Grow Light
Get your plants to produce large, healthy blooms with the Illumitex Eclipse GEN2 LED grow light 4ft bar. The slim design allows for easy connection of multiple lights (up to 15 lights on a single power source), providing bright, uniform F3 spectrum light. The primarily red and blue wavelength is ideal for all stages of plant growth, especially once a plant starts flowering.
- Full F3 light spectrum
- Light-weight at 6 lbs
- Coverage: around 3.5 sq. ft. at 12”; 11 sq. ft. at a 26”
- Special design with 50° beam angle ensures maximum light distribution
- Can be chained together with up to 15 lights using the included 9-foot long power cord
- Internal dimmable driver (0-10V)
- Dust-resistant, waterproof, and damp-proof
- 5-year product warranty
Best choice for vegetables: AntLux 4FT LED Grow Lights
If you’re looking for an affordable, effective grow light to overwinter vegetables such as leafy greens, the AntLux LED grow light is a good option for you. This grow light comes in a pack of 4 and you can daisy chain up to 10 together on a single power source to light up an entire small greenhouse.
- 50W
- Mainly blue and red light spectrum
- Each light weighs about 3.4 lbs
- Coverage: about 16 sq. ft. at 8”; 27 sq. ft. at 12”; 41 sq. ft. at 16”
- Integrated light reflectors reduce light loss and provide excellent heat dissipation; ideal for all kinds of flowers
- Daisy chain up to 10 together with a single power source
- Comes with mounting/hanging hardware
- 5-year product warranty
Best choice on a budget: Monios-L T5 Grow Lights
If this is your first time buying grow lights for your greenhouse, and you don’t want to invest too much, the Monios-L T5 LED grow lights are affordable and highly effective. These come in a pack of 6 and can be daisy-chained together. If you want to set up more than this, you’ll need multiple power sources.
As you would expect from a budget grow light, these boast no fancy features such as dimming, but the full spectrum light will still support healthy plant growth at all stages.
- 20W
- Full light spectrum (380nm to 780nm), available in pink, white, or yellow (soft white)
- Available in 4ft and 2ft lengths
- Mounting hardware included (3 choices: zip ties, screw, double sided tape)
- Space 6-40” from plant canopy, with closer providing more bright light to the plants
- 2-year product warranty
18 comments
Please tell me, how many and what kind of LED lights do I need for a 5′ x 10′ greenhouse. thats all I want to Know, I have been asking that question all over the network and nobody can give me a straight answer.
Hi John, that’s probably because there is no straight answer. It depends on which product you’ll pick and how many plants you’ll grow. If you plan on utilizing both sides of your greenhouse, you’ll need to cover about 20 ft in length. Now, one of our products (Illumitex Eclipse GEN2 LED Grow Light) is 4ft long. Considering that light will cover a broader area, you could use 2 units on each side. You could probably go with 1-2 units in total if you’re not growing on each side because 5ft isn’t very wide. I hope this is a better answer for you but this is a much as I can do without know how your shelving plan looks like.
Hello, we have a 30′ x 80′ community greenhouse in the far north of Canada. 90% of it is plant beds. We grow vegetables like radish, carrots, tomatoes, spinach, lettuce and so on. I’m most interested in fast crops that we can provide a steady food supply. Tomatoes and slower crops are the exception.
I would get white, blue and red LED lights. I would like advice on what light model would be most efficient to operate and cover the area.
I would like for them to be waterproof as well.
I would like to have your advice please.
JS
Hi James! Your budget and usage rates will help determine the best product for you. With a size of 30’ x 80’ you will need multiple units to provide adequate lighting for the area. The products mentioned in this article are excellent choices with a varied spectrum of white, blue and red light. These products can handle humid situations, though they are not considered waterproof. They would not withstand a direct stream or dripping of water.
Hi I have a 6ft by 4ft Greenhouse and would like to know which light would be best to use for all of my garden potted plants. I will be filling the floor of the Greenhouse. Some of my plants are lupins cannas begonias etc. I would like one for day and night on a timer? Can you pls advise?
Thanks
Hi Taylor! For best results you will need to create different, varied levels of lighting with the plants you have named. Begonias require low light and cannas require full sun. We recommend researching the plants you plan to grow and grouping plants according to their needs. In this case, you can use one grow light and group the low light plants on the sides where there is less light from the grow light.
As far as lighting options, LED options are very popular, energy efficient, and can be placed on a timer to cycle off at night. This period of darkness is important for most plants to rest. One grow light like the GENESIS LED Powered Grow Light System GL600 would work well for an area of up to 16 sq. ft. You could also add more lights and a multi-zone timer as your collection grows, since you are growing plants with different sunlight requirements.
Tired or replanting my outdoor potted plants every spring (lantana, hibiscus, mandavilla). SO, this winter want to build a small indoor/garage greenhouse to “winter” my potted plants. Will be cutting them back a bit. My plan is a 6′ w x 10′ l x 8’h plastic wall/PVC frame structure. Have plans for small heater to maintain temp and fan for circulation. What would you recommend for lighting? Plan on about six hours a day and don’t plan on “active growing”. Appreciate your website and information!
Hi Danny! Sounds like you will have a great overwintering space this year. LED options are very popular, energy efficient, and would work well to mimic natural sunlight. A LED like the Dimgogo LED Greenhouse Grow Light System that we mentioned in the article is an economical choice for this space. You can put it on a timer to provide light for 6 hours.
I am constructing a greenhouse 8’ X 20’ with shelving along one long wall. I think LEDs are preferable. What do you recommend and should the lights be adjustable in height?
Hi Arthur! LEDs are a popular choice for lighting and a solid choice for many growing scenarios. Your lighting needs will partly be determined by what crop you are choosing to grow in your greenhouse. LEDs are efficient and long lasting, and available with both blue and red light spectrum colors. They emit low amounts of heat and will not substantially contribute to the temperature of the greenhouse. If you are looking for the lights to produce a significant amount of heat; however, you may wish to explore lights that emit more heat such as incandescent or high-intensity discharge (HID) options.
If you choose to start with seedlings and plan to use the same lights throughout the growing cycle, it may be worth considering adjustable lights to raise the height as your plants grow. Again, this will be dependent upon the growth pattern of the plants you choose to grow. If they are very upright growing, they may require more of an adjustment to keep a reasonable distance from the grow lights.
Good luck with construction and growing in your new greenhouse!
I am getting a 4.6 ft x 2 ft greenhouse for my balcony. I will be growing microgreens and herbs. In the winter I will be housing my aloe plant, orchid and two bonsai trees. I need to know what grow light and/or heater I need to use without overheating or using too much light.
Hi Lisa! For more information on heaters, our post on Best Greenhouse Heaters for the Cold Season may have useful information. You may not need a heater if the location is very sheltered and the greenhouse you choose has quality insulation. Since it is a small space, it will not require much to heat. You may want to consider purchasing a simple indoor grow light and small electric space heater that has an automatic shutoff/thermostat.
I was given a 12 X 8 factory built clear plastic tin greenhouse and it has a thermostat fan in it. It is in very open sunny area except for the tree line about 15 feet on one side to protect from wind. Do I need a grow light? I have some tomato plants in there and I plan on putting house plants in there for the winter.
Hi Noley! Tomatoes need about eight hours of sunlight for production. If you have tomato seedlings, they will require more hours of light, about 14-16 hours. Where you are located will have an impact on how many hours of sun are received and the location of the treeline will also impact if the greenhouse is shaded.
I will have a 14×14 greenhouse with 10ft peaked roof. I want to grow food year around, including a couple of dwarf citrus trees. I live on the North Oregon coast, so lighting will definitely be needed. I have six raised beds 5x3x22″tall. I’ve done quite a bit of reading and I’m now more confused than when I started! I guess I had no idea there were so many options, not to mention just about everything I read is all about growing cannabis, which I’m not going to grow. Any recommendations? Thanks!
Hi Lorinda! Citrus trees will need six to eight hours of sunlight per day on average. Having raised beds already in place is a wonderful first step in your greenhouse. For citrus, you will want to place your lights 12 to 18 inches above the canopy for best results. LED lights are a good option that will have the needed spectrum of light, are cost effective, and energy efficient. I hope this gives you more needed information. Good luck with your greenhouse garden!
Hi! I have a sunroom that I want to grow annual flower seedlings for hanging baskets in, as well as the spring vegetable seedlings that I transplant into my raised beds in spring. Last year was the first time that I tried growing the vegetable seedlings in my south-facing 17x 12 room. I used 2 -3’L x2’W pieces of plywood on three sawhorses for grow tables. I also used a suspended adjustable grow light that only covered 3/4 of that area well, so I was moving trays a lot. Not efficient, but I managed to make it work for the most part with constant adjustments. Oh! The ceiling is only about 7’H with a 12″ pitched roof. I was thinking to add about 4 more table set ups for the 6 – 72 cell trays of flower seeds. Would trying 2 – T5 systems work for this? Is the ceiling too low for that? Or what do you suggest?
Hello Michelle! T5 grow lights are often favored over other types of grow lights for seedlings because they are less harsh on young plants. To figure out the size of the system you’ll need, you’ll just have to decide how many greens, clones, or seedlings you’d like to grow. Four-bulb 24w T5 fluorescent lights will give your plants a total of 8,800 lumens. The footprint would be around 2ft x 14in at 12 inches above your plants. To begin with, hang it about 4 to 6 inches above the tallest plant, for vegging or flowering. The T5 fluorescent grow light distance for seedlings should be a bit further away. I’d start by hanging the light 6 to 10 inches from seedlings. Hope this helps.