Can plants grow with heat lamps instead of sunlight? At first thought, why not? After all, heat lamps emit both light and heat, right? On second thought, plants need more than just heat and light from artificial lights.
Plants can be grown under a heat lamp that is designed to: 1) emit full-color spectrum lights, 2) allow lighting control to simulate day-night cycles, and 3) provide the right photosynthetic active radiation (PAR), which is essential for plant photosynthesis.
Mostly, however, people who don’t know this have plants in their offices or grow plants indoors during winter or for private joy. To be sure if plants grow under a heat lamp, read on. This one’s for you.
Heat lamps are electric lights that emit invisible infrared light to heat the air. Infrared light can help plants grow and bloom. However, it can also damage or even kill plants.
How heat lamps work: A heat lamp is also called an “infrared heater” because the lamp converts electricity into light and heat as well as emits infrared light. The filament in the bulb glows white-hot as it produces heat.
Heat lamps are hot (duh!): Heat lamps of 250 watts produce more heat than 100-watt incandescent lamps. The bulb has a ceramic base so that it won’t melt from the high heat. While electric lights are designed to spread light in a room, the reflector in a heat lamp focuses the light and heat on the plants.
Lights for blooming: According to research published in the American Society for Horticultural Science, plants cultivated indoors can grow well under ordinary fluorescent lights. However, they will not bloom until they are exposed to infrared lights such as incandescent light bulbs.
Lights for stem growth: Research also tells us that far-infrared light (such as this one from Amazon) helps plants to grow longer stems, while ordinary red light can result in shorter stems. While lights that are too red can result in long and thin stems, a combination of far-red and red lights resulted in the best stem growths.
LIghts that damage: A plant can be damaged by too much-infrared light. Heat can discolor or even kill plants, particularly those that lack water. So, for indoor gardening, using the correct infrared balance is important. A light meter can help you make sure that your plants are getting the correct light percentages.
Whether you’re a basement or a windowsill gardener, there’s no question that your plants need light and warmth to thrive, and heat lamps emit light and warm the air. Here are five (5) common reasons why plant growers use heat lamps.
Convenience: Heat lamps can be used to control the air temperature of indoor gardens, as well as to grow plants privately, particularly in places where some plants are not considered as legal. As well, heat lamps can be moved and adjusted for focus and distance to plants.
Lower costs: Research shows that infrared heating can reduce heating costs by 17 percent and gas consumption by 31 percent compared to conventional gas heating systems. As well, high quality crops can be grown and uniform temperatures can be maintained.
Accelerated growth: Research indicates that infrared heating can accelerate the growth of seedlings. However, we are talking about seedlings! This does not apply to grown plants. Indeed, seedlings need a warmer than usual environment to grow, and so why the heat of a heat lamp is used in this case.
Higher production yields: Heat lamps can be used as grow lights to help plants grow indoors, even in winter. Thus, infrared heating can continue crop yield production even in inclement weather by protecting plants field frost, as well as from extremely low temperatures.
Control conditions: Unlike natural sunlight and weather conditions, growing plants under well-designed artificial lighting can control elements such as humidity, temperature, and the like. At the same time, there is better control against pests, pathogens, and herbivores that can destroy plants.
On the other hand, many believe that artificial lights are not good for plants. One reason is that sunlight, along with night-day cycles and weather elements such as winds, clouds, and the like, are signals that plants use to start processes such as photosynthesis, budding, flowering, germinating, and so on. These natural cues are absent when only artificial light is used.
Here’s a summary of eight (8) other arguments against the use of artificial lighting for growing plants.
Technology and expenses required: Unlike natural sunlight, which comes free, the use of heat lamps requires the use of technology (electricity, light bulbs, switches, and the like) as well as the expenses associated with using these.
Not designed for growing plants: Like air conditioners are designed to cool air, heat lamps are designed to heat air. They’re not designed to create the natural conditions for plant growth and development and may disrupt natural processes. At the same time, lamps that heat the air affect humidity levels and this may (or may not) suit the plant’s requirements.
Limited color spectrum: Sunlight has a complete light spectrum (that we can see in rainbows). Plants sense information from light spectrums to determine the season, time of day, etc., which determines growing, flowering, fruiting, and other plant behavior. That’s why heat lamps with limited spectrum can’t help plants to grow well.
Interrupted light-dark cycles: Heat lamps do not provide the natural light-and-dark cycles that are necessary for plants to “rest” and recover from environmental stresses, as well as to take a break from growing and focus on moving and transforming nutrients. Hence, you should always turn it off at night!
Not all plants do well: Low-light plants such as peace lily, pothos, and other plants that thrive in the shade can grow under artificial lighting. However, the research found that ornamental plants grown under infrared lights look unnatural.
Lowers moisture levels: Also, the heat from the lamp turns water into gas, drying out the plant’s leaves and the air around, which is not good for plants that need high moisture, such as ferns, aloes, and calatheas. However, low-moisture plants do well, such as succulents, pothos, verbena, sage, lavender, and red valerian.
Temperature: A heat lamp is designed to warm up the air, so a plant may suffer from dehydration. Plants with thin leaves such as basil may even burn. When using a heat lamp, check with your hand if the distance is safe. Place your hand between the lamp and the plant, with your palm facing down towards the plant. If you feel a “burning” sensation, then it is too hot for herbs and many other indoor plants.
Increase in pathogen attacks: Research indicates that infrared heating can result in increased pathogen attacks on plants and crops.
Best Practices: Choosing a Better Lamp
For indoor gardeners and those who like having fresh herbs growing by their kitchen window, there’s no better alternative to sunlight.
Those who grow herbs under artificial lights may know that mint, bay, rosemary, and thyme can grow in indirect sunlight. Chives, horehound, and winter savory also grow well indoors. Lemon balm and tarragon also grow well, even in low light conditions.
Given the pros and cons of heat lamps, the good news is that you can have a great indoor garden even with artificial lighting. We asked experienced gardener friends and here are their tips for a better grow light experience.
Choose full-spectrum lights: While “full-spectrum” is only a marketing term for artificial lights, technology continues to evolve. Check out a set of plug-and-play, full-spectrum LED grow light bulbs for indoor plants such as this one on Amazon, or a 1000w LED full-spectrum to grow light for indoor plants such as this, also on Amazon.
Choose the right color temperature: For vegetative growth such as herbs and succulents, use a full-spectrum heat lamp with a color temperature in the blue range (5,000 – 7,000K) or in the red range (3,500 – 4,500K) for fruiting and flowering plants. You can try out a set of 3500K dimmable LED grow lights for indoor plants such as this one on Amazon, or some 45W LED red blue-white grow lamps for indoor plants such as these, also on Amazon.
Here are the most frequently-asked questions that I get about using heat lamps to grow plants indoors.
Can I put the bulb of a grow light in an ordinary lamp? Yes. If the bulb has the right wattage and socket type, it should fit into a regular lamp.
Can my plants grow under ordinary office light? Yes. The whitish-blue light of fluorescent lights in offices is fine for plants that are sold for indoor and office use.
What color of LED light is best for my indoor plants? Red, blue, green and yellow. Light with a lot of red and blue as well as a little green and yellow are best for indoor plants.
What is infrared light? Infrared light warms (or heats) anything it touches. To produce the most amount of heat, bulbs are colored to maximize infrared light.
How long should I expose my plants to a heat lamp? It depends on the type of plants. Flowering plants and vegetables need about 14 to 18 hours. Begonias, chrysanthemums, and azaleas need at least 12 hours a day.
Red Light : Plants & Light (6:45 minutes)
How many lumens (visible light) do plants need? On average, about 5000 lumens per square foot but it also depends on the air temperature, type and number of plants, how far apart they are, and the grow light you’re using. Plants that need minimum lighting need only about 2000 lumens per square foot. Flowering plants need 5000 to 10000 lumens while vegetative plants need from 2000 to 3000 lumens per square foot.
Heat lamps are designed to heat air in enclosed spaces. While heat lamps were not designed for growing plants, savvy gardeners now recommend the use of particular heat lamps and tools for better indoor gardening.
The best practices summarized here include: (1) Choose heat lamps that can provide the best growing conditions for plants grown indoors, (2) maintain the soil moisture, humidity, and air temperature that fits your plant’s needs, (3) give your plants enough rest time in the dark, (4) use lights with the right PAR (Photosynthetic Active Radiation), and (5) choose the right plants that will thrive under artificial lights.
I hope that this article helps you as much as it has helped me. If you have any experiences you’d like to share, or if you have questions about growing plants with heat lamps, please let me know. I’d love to hear from you.
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“Artificial Light At Night — The Impact On Plants And Ecology” by the European Commission’s Science for Environment Policy. (SEP)
“Artificial lighting system for plant growth and development: Chronological advancement, working principles, and comparative assessment” by S. D. Gupta, & A. Agarwal (2017) in Light Emitting Diodes For Agriculture.
“A Historical Background Of Plant Lighting: An Introduction To The Workshop” by R. M. Wheeler in Horticultural Science
“High-brightness LEDs—Energy Efficient Lighting Sources And Their Potential In Indoor Plant Cultivation” by N. Yeh & J. P. Chung in Renewable and Sustainable Energy Reviews
“Optimized design of LED plant lamp” by J. S. Chen, et al In International Symposium on Optoelectronic Technology and Application in International Society for Optics and Photonics
“Simulation of climate change with infrared heaters reduces the productivity of Lolium perenne L. in summer” by Nijs, I., , et al in Environmental and Experimental Botany