Can You Use Regular Light Bulbs As Grow Lights?

a grow light bulbGrow lights are expensive. Regular light bulbs are not.

This could be a great way to save money…if regular bulbs work for growing plants.

People often assume you need expensive grow lights to make up for the lack of natural light, but the truth is, you can actually use regular light bulbs to grow plants indoors.

But should you use regular bulbs?

In some cases, yes; in some, no.

And when it comes to LEDs, I would not recommend regular LED lights at all—see the LED section below for more.

Before we get into that, you might be asking yourself how you would know if your plants aren’t getting enough regular light and whether they need artificial light to help them out.

Believe it or not, your plants will tell you. Not literally, of course, but they will show you.

If your plants aren’t getting enough regular sunlight, they will grow tall with weak stems and the leaves will be lighter in color. New leaves will often be larger in size and the leaves on the inner part of the plant may start to turn yellow.

If your plants show these symptoms, you are going to want to get them some additional light. The most successful light bulbs contain both blue and red wavelengths of light. The blue is especially useful for foliage growth and the red is for flowering and fruiting.


Types of Light Bulbs Available

If you just need light for your regular houseplants, any lamp or light fixture will do. Which one is best for you, depends on your needs (see the next section). You do want to make sure the light you choose has the correct color temperature (explanation below in the fluorescent light section), as this drastically improves performance.

The most popular types of light bulbs to use as grow lights are incandescent or fluorescent bulbs, but you can also use LED lights, halogen lights and traditional horticultural grow lights, like high-pressure sodium bulbs (HPS) and metal-halide bulbs (MH). The first two are fine for small gardens; if you’re got a larger grow, LED or HPS/MH make the most sense.

If you are thinking of growing plants from seeds, you’d be best off with hanging tube fixtures that you can place directly over your plants. There are special kits available that include the fixture and reflectors.


Incandescent Lights

incandescent bulb over indoor gardenIncandescent lights are the standard light bulbs we all already have in our homes (here are a bunch of examples on Amazon). They are the cheapest option, but they are inefficient. They use more power to get the same output and they give off a substantial amount of heat. For these reasons, we generally do not recommend using them for your plants.

If you do use incandescent bulbs, make sure you don’t place them too close to the plants. Use the hand test. Place the back of your hand where the plant is and wait a minute. If the light becomes too hot for your hand, it is also too hot for the plant and you need to move it further away.

Incandescent bulbs are usually the first option people consider, because they are cheap and we all already have some lying around the house. But we always recommend fluorescent bulbs. They don’t cost all that much more and they are a lot more efficient: they last longer and use less power, so you actually end up saving money.


Fluorescent Lights

compact fluorescent grow light bulbFluorescent lights are the best choice because they are the most economical.

They are sold in tubes (like these, which are good for larger indoor gardens) or compact bulbs that go into a regular lamp socket. These are called CFLs and are best for a few plants or as supplemental lighting. They are the bulbs we will discuss from here on (everything we say goes for tubes as well, though).

Fluorescent lamps stay cool enough that they can be placed close to your plants and they use much less power per lumen (the amount of light they give off) than incandescent bulbs, which saves you on your power bill.

Many of us also have some at home already. That said, you want to pay attention to the color temperature of the bulb to ensure the best possible performance.

If you don’t mind spending a bit more, you can get a specialized fluorescent bulb (like these) made specifically for growing plants. These have an optimized color spectrum for plants (see the next few paragraphs to help with choosing the right color temperature) and they are also more powerful than regular fluorescent bulbs.

Regular bulbs work just fine, though, especially if your plants are already getting some natural daylight. Generic fluorescent bulbs and tubes are higher in blue wavelength light. This is great if you are growing plants that don’t bloom, like a cactus or herbs. For this purpose, use bulbs labeled as ‘daylight’ or ‘cool  white’. The color temperature on these bulbs will be between 6000K and 7000K.

If you are growing plants that flower or fruit, you will want a bulb with more reddish light. You can still just use regular bulbs, but you want to make sure they are labeled as ‘warm white’ or ‘soft white’ like these. In terms of color temperature, they will be between 2000 K and 3500 K.

Another option is to get a bulb with a color temperature right in the middle, between 4500 and 5500 K (confusingly, these are also sometimes labeled as ‘daylight’). These work for all plants, but are not quite as efficient as cooler bulbs for growth or warmer bulbs for flowering. We find a mix of cold and warm bulbs to work best.

The main problem with both incandescent and fluorescent bulbs is that they aren’t generally powerful enough to flower more than a couple of plants, unless you get a ton of them. Once you get a lot of them, they are no longer cost effective, because there are much more efficient lighting options available. If you have more than a couple of plants, you would be much better off with high-intensity discharge lights (HID) or LED lights.


LED Grow Lights

LED lights are more energy efficient and emit much lower levels of heat than other types of lighting. But can you use any led lights to grow plants?

Generally no. Because LED technology is so customizable, every bulb is different and you need bulbs that produce the exact red and blue wavelengths required by your plants. For this reason, most general LED lights are not effective for plants.

Luckily, there are horticultural LED grow lights available, which produce only the wavelengths used by plants, so you will want to look at purchasing these, as opposed to just general-use lights. They are not cheap, however. That said, there are a few quality, inexpensive LED plant lights on the market.


Halogen Lights

Halogen lights also provide full spectrum light and are quite powerful, but they are similar to incandescent bulbs in that they emit a lot of heat and are not as energy efficient as fluorescent lights, HID lights or LED lights.


HID Plant Lights

Finally, we come to traditional horticultural grow lights (if you already know you want to go with HID lighting, head here for help in choosing the right ones). These are often referred to as HID lights and are further broken down into HPS and MH lights.

HPS bulbs emit more of a red spectrum light, making them superior for flowering and fruiting, while MH bulbs emit more blue light, making them ideal for plant growth.

HID bulbs are very energy efficient, but because they are so powerful, they still use a lot of power and emit a lot of heat. They also require additional components like a ballast.

Since they give off a large amount of light that is powerful enough to flower any plant, HID lights are still the light of choice for most commercial indoor growers, although LED lights are slowly taking that crown (read more about HPS versus LED lights).

For most of us, HID and LED lights are far too powerful and expensive for our needs. But if you have a larger garden, you’ll definitely want to go with one of these options. If you decide on HID lights, we have a post helping you choose the best one for your needs.


How to Set up the Lighting

For a small garden of a few plants in a room with very little natural light, a standing lamp with three bulbs and a movable or goose-neck feature works well. Use fluorescent bulbs with the highest wattage allowable by the fixture for the best results.

You want to aim the light towards the table with the plants. If your light fixture does have a movable arm, place the fluorescent bulbs closer to the plants than an incandescent bulb. This is to avoid heat damage, if using incandescent light.

To make more efficient use of the bulbs, place a reflective surface, such as a mirror or just some reflective foil, underneath the plants, so that the light can reflect back up towards the foliage. And finally, attach and set a timer to run the lights for 14 to 16 hours a day. You can do this manually, but it is easier with a timer and even a quality one like this one doesn’t have to cost a lot.


February 9, 2017

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