Fluorescent Light And Plants: Lighting Options For Indoor Gardening

By: Bonnie L. Grant, Certified Urban Agriculturist

The right kind of grow lights can make all the difference in how your plants perform. Using fluorescent garden lights to enhance plant growth allows you to grow a host of plants in an interior space. Standard indoor lights do little to influence photosynthesis, while using fluorescent lighting placed closely to the top of the plants can help drive this important plant process.

About Fluorescent Light and Plants

Modern plant lighting has focused on the LED sources of light, but fluorescent lights are still widely available and easy to use. Fluorescent lights don’t last as long as LEDs but are easy to find and install. Whether you use them vs. LEDs depends upon the light requirements indoors that your particular crop or plant needs.

Fluorescent lights were once the “go to” source of plant lamps. They fell out of favor because they don’t last very long, are delicate, bulky, and don’t provide a high lumen intensity. Therefore, the bulbs are not ideal for fruiting and flowering plants. Modern fluorescents, however, have increased the lumen output, come in compact bulbs and last longer than their predecessors.

In fact, new T5 lighting systems produce less heat than the old bulbs and can be placed closer to the plant without worrying about burning foliage. They are also more energy efficient and the light produced is readily used by the plant.

Determining Lighting Requirements Indoors

A good light meter can help you determine how bright you need to make the light system. Light for growing plants is measured in foot candles. This measurement indicates the amount of light given off a foot (.30 m.) away. Every plant needs a different amount of foot candles.

Medium light plants, such as tropical rainforest specimens, need around 250-1,000 foot candles, while high light plants need over 1,000 foot candles. You can increase the amount of light a plant receives even with a low output bulb by using a reflector. These can be purchased or use aluminum foil to focus light.

Fluorescent Lighting Options for Indoor Gardening

If you are considering using fluorescent lighting, there are a couple of systems to consider.

  • The new T5 fluorescent garden lights are tube lights which provide light on the blue spectrum and are cool enough to touch safely and won’t burn young plants. The number 5 refers to the diameter of the tube.
  • There are also T8 tubes that are similarly efficient. Both produce plenty of light but are of a lower wattage than older fluorescents and, therefore, more economical to operate. Purchase tube lights with an HO rating, which indicates high output.
  • Next are the CFLs or compact fluorescent tubes. These are great for small grow spaces and can be used in an ordinary incandescent light fixture.

No matter which you choose, fluorescent light and plants will increase growth and output in interior situations.

This article was last updated on

Read more about General Houseplant Care

Indoor Lighting

Indoor Lighting

Growing carnivorous plants indoors is practical and convenient. One major consideration is providing sufficient light. Since most carnivorous plants develop their best color and flowering in bright light, it is important to provide good lighting. This can be accomplished indoors often by placing the plants on or near a bright window sill. However artifical lighting extends your indoor growing area.

I have found that plant carts, large or small, are a great way to pack a large number of plants into a small area. Hanging a simple shop light over a tray of growing carnivorous plants is an easy arrangement. Keep in mind that light intensity and duration are important considerations. Common white light fluorescent lights placed about 6" above the plants, and run on a timer set for 14 hours a day is a good basic set up for indoor growing. Lights can be placed from a few inches to a foot above the plants and experimenting with height is worth the effort. Also consider a longer light period for the timer, or adjusting the time seasonally to mimic outdoor growing. 16 hours summer, 14 hours fall/spring and 12 hours winter. I have not yet found a timer that can be set for seasonal variations. Varying the length of daylight will help induce flowering.

Which fluorescent bulb to use? My days teaching Physics and Biology have taught me that plants appear to be green in color because they are absorbing all colors of light except green. They reflect this back to our eyes, and thus appear green. What this means for growing, is that plants use the red and blue ends of the spectrum for their photosynthetic needs. Blue light tends to favor leaf growth, and red light tends to favor flowering, seed and root growth. Though most fluorescent lights look like they are giving off white light, there are important differences in the intensities or range of their spectrums or light frequencies. These are described by the manufactures as color temperature. Soft White at 2700K offers a yellowish light, Cool White at 4000-5000K provides a slightly blue light, Daylight White at 5000-5900K is much bluer white. Grow Lights (Plant/Aquarium) are designed to enhace both red and blue frequencies for plants and provide a wider temperature spectrum. They glow at a slightly pink color and are typically twice the price of more common fluorescent tubes. I prefer the Grow Lights, but have had success with Daylight White too.

LED (light emitting diodes) designed for plants are becoming more available. These tend to be a combination of red and blue LEDs, and sometimes provide an unnatural looking glow. They are less expensive to operate.

Aquarist and coral growers often use Metal Halide lighting. I find this too bright and costly to operate for my preference.

Other Considerations

  • Keep in mind that most light and/or their ballasts produce heat. This can be troublesome in a closed terrarium, so keep a thermometer with the plants to monitor heat.
  • Be sure to keep the humidity up for your indoor carnivorous plants by growing them in a water tray, open terrarium or within a plastic tent.
  • A reflective surface such as mylar or aluminum foil can help reflect more light back onto the plants.

What is a regular fluorescent light bulb?

Heating the gas inside a fluorescent tube/bulb with the help of electricity and turning the produced ultraviolet rays into visible light through a phosphorus coating as well as a ballast behind it is the ultimate procedure to emit light.

If we talk about masses, they exhibit more comfort in fluorescent tubes to light up their home rather than fluorescent bulbs. Other than that, covering large grow space with fluorescent tubes are also a profitable idea.

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Lighting options for starting seed (LEDs vs. Fluorescent)

In last month’s article, we discussed some of the indoor gardening tasks that fill the winter void for green thumbs and help prepare gardeners for greater productivity come spring. One of the reoccurring topics of interest in the horticulture wing of our office has been seed starting and artificial lighting options for growing indoors. As anyone who has relied on the light from their house fixtures and a south-facing window know, plants need greater light quantity and quality for healthy growth. And when gardeners want to get a jumpstart on their annual herbs, flowers and veggies, dedicated grow lights are necessary to produce quality plants from seed.

This topic of conversation has evolved over the last 10 years alongside advances in lighting technology and the increasing amount of ‘grow light’ products now available to consumers—especially online. Extension’s recommended setup for starting seeds indoors typically features a PVC stand and fluorescent shop light setup . But everybody’s heard about the benefits of LED's (light-emitting diodes), their touted efficiency and longevity. When it comes to horticultural lighting there are many options (including high-intensity gas discharge lamps or HID's) but for the average home seed starter, LEDs and fluorescent lights are the main options. What is the difference and how do you choose?

The lights in this category are tried and true. They are significantly more efficient than the once common home incandescent bulbs. In simple terms, fluorescents use their energy to produce more light than heat comparatively. And there are two types commonly employed for starting seeds, tube types and compact fluorescent lamps (CFL's). For folks that are pretty new to growing indoors or have a small space, the CFLs can be a great option. These compact types fit into a standard lamp socket, unlike tubes that require a ballast/shop light fixture.

CFLs benefit from use with a reflector to focus the light on plants.

However, because of their shape and expanded surface area tubes are typically more efficient than CFL and fit well into a shelving system. The T5, T8 and T12 bulbs are the most common tube types. Bulbs are classified by T for tube and the number represents their diameter 5 = 5/8”, 8 = 8/8 or 1”, and 12 = 12/8” or 1.5”. T8s and T12s fit most standard shop light fixtures. High output T5s (HOT5) are considered as the most efficient and best in terms of light quality for fluorescent plant production but they will require a special fixture that is less often found at the hardware store.

Whether you’re using tubes or CFLs, fluorescent lighting should be kept close to growing plants (within 1-2” of plant tops) and the area they can effectively cover is limited to the surface area of the bulb. For example, when growing seedling in a standard 10 x 20” seedling tray you’ll want four tubes or two shops light fixtures (

5” wide) to cover the 10” tray width, otherwise your plants on the edges will stretch towards the middle (pictured below).

A new technology, compared to the other lighting options in the horticulture world. LEDs are unique in their ability to produce a high quantity of light with lower energy requirements—some models producing more than twice the amount of light per watt compared to fluorescent. Some LED systems are designed to improved efficiency by delivering red and blue spectrums of light exclusively (the wavelengths required for plant growth). This is why some LEDs give off a purple glow, unlike full spectrum lights that emulate daylight. But as we know, LEDs, like those available for home lighting, come in more neutral white colors that will also work for seed starting. You can even buy led tube lights that will fit in your shop light ballast and require less energy. (pictured below).

Balanced spectrum, White LED tube in normal shop light fixture

Now for someone like a hydroponic lettuce grower operating a hundred lights and thousands of watts per hour (kWh) the cost-benefit of LEDs (especially the red and blue dual-band types) vs fluorescent will be highly tangible. For a home seed starter, you’ll be running a couple of lights at a hundred watts for a few weeks. The energy savings and cost in your scenario may only amount to a few dollars. The lifespan of LEDs is also notable with some types lasting 2 to 4 times longer than the average fluorescent. But again, even a fluorescent bulb is rated for 10,000 - 20,000 hrs and will likely be used for less than 1,000 in a typical spring seed start endeavor. Lights can be left on for up to 24hrs during the seedling stage but at minimum 14 to 16 hours each day for best growth. Because the quality of light is less from the lights than light from the sun, artificial lights must stay on for a longer period than normal day length. Some LEDs are more susceptible to degrade when running for more than 18 hr during the day—follow instructions provided with your light.

One last thing to be mindful of when purchasing LEDs, especially the red and blue grow lights, is the distance you’ll want to position the light from your plants. Unlike fluorescents, which should be positioned roughly 1” above the tops of growing seedlings, because of their greater efficiency and higher photosynthetic active radiation (PAR) some LEDs can be held at higher distance from plant tops. If your seedling leaves look bleached, move the light back and if the seedlings are stretching or leggy bring it closer till you find the sweet spot. With both LEDs and fluorescent look for lights that include the cooler blue spectrum, these will often be marked as 5000-6500K (Kelvin). And avoid the hundred dollar plus LED options that tout hundreds of watts, UV and Infrared spectrum as these are not required for good seedling growth

Dual-band LED, better photosynthesis efficiency and so light can be held at a greater distance from plants.

Have questions? The Garden Hotline is staffed by trained EMG volunteers and Extension staff who will assist you with questions.

Fluorescent Lights

Fluorescent lights are ideal for plants with low to medium light requirements, like African violets. They are also good for starting vegetables indoors. These lights typically come in long, tubelike bulbs in a range of sizes including T5, T8 and T12.

The narrower the bulb, the more efficient and brighter it is, due to the smaller surface area. In addition to this, fluorescent bulbs use 75 percent less energy than incandescent lights. So, for example, a 25-watt fluorescent emits about as much light as a 100-watt incandescent light bulb. T5 systems put out about double the amount of light per tube as standard fluorescent lights. They are 6500 Kelvin and also full spectrum, which is very intense light.

Kelvin is a basic unit of color temperature used to measure the whiteness of a light's output it's the degree of visual warmth or coolness of a light source. So the higher the degree of Kelvin, the bluer, or "cool," the lamp appears. The lower the degree of Kelvin, the redder, or "warm," it appears.

When growing most houseplants, use light bulbs between 4000 and 6000 Kelvin, as the bulb's color temperature will borrow from a full spectrum of colors—cools and warms. With these lights, you can actually mimic the growth you would get in a greenhouse or outdoors. Culinary herbs, greens and starter plants can be grown year-round with them. Houseplants that need lots of light, like cattleya orchids, succulents and carnivorous plants, also perform much better under these full-spectrum lights. With starter plants and seedlings, place the T8 or T5 bulbs two to four inches from the plants to mimic the sun. For established plants, including herbs or houseplants, place them a foot or two from the light source.

Best Light for Growing Plants Indoors

Growing indoors? Get the lowdown on choosing lights for your indoor plants.

Related To:

Plant Lights

Investigate the variety of plant lights available to increase the rays your plants receive, especially in northern regions in winter. New light technology provides full spectrum rays from models small enough to fit on a tabletop.

Photo by: Gardener’s Supply Co. at Gardeners.com

Gardener’s Supply Co. at Gardeners.com

Investigate the variety of plant lights available to increase the rays your plants receive, especially in northern regions in winter. New light technology provides full spectrum rays from models small enough to fit on a tabletop.

Plants need three things to thrive: soil, water and sunlight. Soil and water are easy to come by, but if you’re planning to grow anything other than houseplants indoors, providing sufficient sunlight presents a challenge. Even if your house or apartment has plenty of windows, you likely won’t get sufficient sunlight to keep your indoor garden happy, especially during winter.

That’s when you bring in the “sun” in the form of artificial lighting. “With the right lighting, you can grow peppers, tomatoes, cucumbers, herbs – a wide range of edible plants,” says Paul Thompson, an indoor-garden expert at All Seasons Gardening and Brewing Supply Co. in Nashville, Tennessee. The lighting you choose depends on the area you need to cover and the light requirements of the plant.

How Much Light Do Vegetables, Herbs, and Fruits Need?

Understanding basic light levels and how different plants respond to light is your first step to indoor gardening success. People and plants "see" and use light differently. What looks like a bright lamp to you might not be very efficient for plant growth. Light provided to your plants from grow lamps needs to be within the right spectrum for good photosynthesis. Lamps must also provide enough volume of light for the type of plant you're growing. Skip the shop lights. Quality, efficient grow lamps that generate more light and less heat are your best bet. New innovations in LED grow lamp technology have made them good choices for growing seedlings, leafy greens and herbs, and small fruits indoors.

Edibles will require more light than your average houseplant. If your indoor light levels are low to moderate, and your light source is farther away from your plants, stick to leafy greens and shade-tolerant herbs. Sun-loving foliage herbs, such as basil and thyme, will need medium to high light levels indoors with a closer light source. Fruiting plants, such as tomatoes, peppers, and citrus, will need the highest levels of light. Germinating seedlings also fall into the high-light category.

Grow Lighting Tip: You can increase your light levels, to simulate full sun conditions, by moving your plants closer to the grow lamp. You can decrease your light levels, to simulate part-sun to shade conditions, by moving your plants farther away from your grow lamps.

Growing Leafy Greens and Herbs

If you're just getting started, try growing low- to moderate-light tropicals and edibles. Leafy greens, such as many varieties of lettuce, mache (corn salad), watercress, sorrel, spinach, and kale grow in moderate light levels. If you think about how these plants grow in the outdoor garden, they can be maintained successfully in conditions that are partly shady. This also applies to cool-season herbs in the carrot family, such as parsley, cilantro, and fennel — as well as mints.

Some edibles, such as leafy greens, can grow in bright windowsills indoors, but in areas with less natural light, you'll need grow lamps for a good harvest. These lettuce plants are growing under the high-output LED lamps in the Low Bamboo LED Grow Light Garden.

Most leafy greens and cool-season herbs have a compact to medium-sized growth habit that is perfect for small spaces such as your kitchen or living room corner. Your light source can be a little farther away from these leafy crops, as they don't require intense light levels to thrive. Use a light timer to keep your grow lamps on for approximately 12 hours a day. If your light garden is situated next to a bright window, you may be able to leave the lights on for fewer hours per day.

Fertilizer Tip: Leafy greens and herbs aren't heavy feeders, but since you'll be harvesting from them regularly, be sure to feed them monthly with a natural liquid fertilizer that contains humus or seaweed, such as Plant Health Care for Seedlings & Houseplants.

Germinating Seeds & Growing Microgreens

When you're ready to get new seedlings started, or grow fresh microgreens, you'll need to step up your light levels. Seedlings are light-hungry: they require long durations of bright light to sprout successfully and vigorously. Too often, beginners attempt germinating seedlings without enough light, resulting in weak, stretched seedlings that eventually topple over and die.

Use a light timer to leave your grow lamps on for an average of 16 hours per day for young seedlings. If your light garden is next to a bright window, you can run your lamps for 14 hours. If your space doesn't have much natural light, you can run your lamps for up to 18 hours. Watch your seedlings to see how they perform.

In most grow light setups, the light source also needs to be very close to the tiny seedlings to provide enough light: as close as 3 to 6 inches. The high-output LEDs in the Bamboo LED Grow Light Gardens provide adequate light for seedlings to thrive up to 8" from the bulbs. (GSC photo.)

One major benefit of using LED grow lamps to start seedlings is that these lamps do not generate much heat. That means you can keep your young plants closer to the lamps to give them high light levels, without burning them.

Once your seedlings have new true leaves and are ready to be transplanted into larger containers, the transplants can be moved a little farther away from your light source — or moved from the 12" (Low) Bamboo LED Grow Light Garden unit to the 30" Medium Bamboo LED Grow Light Garden.

Fertilizer Tip: Seedlings can burn from over-fertilization. Use a natural liquid fertilizer, such as PHC Plant Health Care for Seedlings & Houseplants, at 1/4 the recommended strength to feed your seedlings weekly.

Alpine strawberries flowering and fruiting in a Low Bamboo LED Grow Light Garden.

These cherry tomatoes were grown in a Bamboo LED Grow Light Garden in the Gardener's Supply Testing Lab. Small-fruited tomatoes like these are a better choice for growing indoors than large-fruited varieties. (GSC photo.)

Grow Fruits, Roots, and Sun-loving Herbs

When your heart is set on growing sun-loving fruits and herbs indoors, quality grow lamps are a must. Producing flowers, fruits, and large roots takes a lot of energy, so plants need intense light levels for longer periods. Crops such as tomatoes, peppers, beets, strawberries, and basil thrive and produce outdoors in full sun conditions, where they typically receive direct sun for 6 to 8 hours per day. You'll need to replicate those conditions with your grow lamps indoors.

For small space indoor growing, choose compact or dwarf fruits such as mini cherry tomatoes, compact peppers, mini-beets, or day-neutral strawberries (alpine strawberries are a good choice). The Bamboo Light Garden easily accommodates strawberries and mini-tomatoes and peppers in the 12" fixture, and compact tomatoes, peppers, and herbs in the 30" fixture. Your light source will need to be about 6 to 12 inches above the plants to provide enough light. You can always prop up shorter plants to place them closer to the light source.

Sun-loving crops will need the high-output LED grow lamps turned on for 14 to 20 hours per day, depending on the type of plant and the ambient light in your space. If you can place your Bamboo LED Grow Light Garden next to a window you can further boost light levels. If plants are not growing vigorously or flowering enough to produce good fruit yields, leave the lamps on longer.

If you keep larger fruiting edibles in containers during the warm season, it can be a challenge to keep them healthy once you move them indoors for the winter. You can overwinter dwarf citrus plants, compact figs, and many other tropical container plants and houseplants in the Tall Bamboo LED Grow Light Garden.

Fertilizer Tip: Fruiting crops are heavier feeders, so fertilize twice monthly with a natural liquid fruit or vegetable fertilizer.

You might have noticed that not all quality and powerful grow lamps and fixtures are attractive. Meaning, you wouldn't want to hang them in your living room! The Bamboo LED Grow Light Garden's good looks are right at home in any living space. They're available in three heights fit for seed starting and high-light plants, leafy greens and herbs, and larger container tropicals and edibles.

For more in-depth information on growing edibles and ornamentals indoors with grow lighting, check out Leslie's book Gardening Under Lights: The Complete Guide for Indoor Growers, published by Timber Press.

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