Light Meter for Plants: Your Best Options in 2021!

Purchasing a light meter for plants can be game-changing.

A light meter can provide you with a lot of valuable information that will help you increase the growth and yield of your plants.

Light meters vary in type depending on what aspect of light they can measure.

In gardening, the most commonly used light meters are ones that measure lux (or lumens) and others that measure PPFD.

light meter beside a plant

PPF and PPFD are the most relevant measurements of light for plants. They can assess the intensity of photosynthetically active radiation (PAR), the range of light that plants use. 

Lumens, lux, and foot-candles, on the other hand, can give us information about the overall intensity of light but not its quality.

That said, a PAR meter, also known as quantum flux or PPFD meter, usually costs a lot more than a lux meter because it provides more specific data about light.

It’s important to note that you might not always need a PAR meter and a lux meter can sometimes be enough.

In this article, we will discuss that topic in detail and we will examine the best light meters for plants.

A Lux Meter Can Measure Overall Light Intensity

The source of all direct sunlight is one, the sun. So, the quality of sunlight is nearly always the same.

That means you don’t need to measure the PAR output of sunlight.

Instead, you need to focus on finding the intensity of sunlight that your plants are receiving.

We can learn that by measuring lux or lumens instead of PPF or PPFD, and a lux meter can get the job done in this case.

Without a doubt, the best lux meter to use for plants is Dr.meter 1330B.

Dr.meter 1330B

Unlike many other lux meters, Dr.Meter 1330B has an amazing design that makes it very flexible.

The lux sensor is connected to the device via an elastic coiled cable that you can stretch to reach different spots around your plant.

The meter is widely used in laboratories and photography studios as well as in growing setups.

Dr.Meter 1330B is very sensitive to light and can also measure very intense lux (up to 200,000).

The device is a best seller on Amazon in the category of light meters and has a lot of positive reviews.

Dr.Meter 1330B is very affordable, so if you belive you need a lux meter, this is your best option.

How to Use a Lux Meter With Your Plants?

Use a lux meter to measure light intensity at the level of the leaves so you can obtain useful readings.

Also, remember to measure light at different hours of the day in various locations around the house or the growing area.

How to Understand Lux Readings?

To make use of your measurements, you should first learn about the light requirements of your plants in terms of lux.

Keep in mind that on a sunny day outdoors, direct sunlight measures about 110,000 lux, while it measures about 1100 lux on a cloudy day. 

Considering that, plants have different requirements for light depending on the climate in their original habitat.

To make it easier for you, gardeners have classified plants into three categories according to their light needs: low-light or partial shade plants, medium-light or partial sun plants, and high-light or full sun plants.

Very low-light plants can thrive on around 1000 lux, while medium-light plants need about 35,000 lux.

High-light plants need at least 50,000 – 60,000 lux to thrive. In fact, some full-sun plants need far much more than that.

You can check any gardening encyclopedia to learn about the light needs of a plant, and you can learn more about lux requirements for plants here!

rose plant
Roses are High-Light Plants

By referring to the above information, your lux readings will allow you to decide where to locate your plants around the house.

If you find that the light intensity around your house is not enough for your plants, invest in supplemental LED grow lights.

A PPFD Meter Can Measure the Intensity of Useful Light (PAR)

Using a light meter for plants growing under lights is a different story. And to be honest, it’s a bit more complicated too.

Testing artificial light is usually done to assess light intensity, quality, or both. 

The quality of light varies significantly from one grow light to another. Some grow lights produce more PAR or different light frequencies than others.

So, even if a lamp emits 20,000 lux, that doesn’t mean you can grow plants under it. 

You should know the amount of PAR that a lamp puts out before attempting to grow any plant under it.

In case you can get the PPF or PPFD measurements of your grow light from a credible source on the internet, you won’t need to measure them again. Accordingly, you can only use a lux meter to measure the light intensity at the level of the leaves to decide whether you should raise or lower the fixture. But, this approach isn’t the best.

If you want pull the highest yield from your plants, you will benefit from having a PPFD meter.

The best PPFD meter found on the market is Apogee MQ-500 PAR Meter. It is the most commonly used light meter by professional indoor gardeners.

Apogee MQ-500 PAR Meter

Apogee manufactures several different PPFD meters, but MQ-500 works for all light sources, including LEDs.

The company advertises MQ-500 and other PPFD meters to scientists, so you can expect their devices to be very accurate.

Apogee MQ-500 is very sensitive and responsive. You will be able see the PPFD measurements in real time as you move the meter around the growing area.

The instrument can be used in different growing environments because it is sturdy and waterproof.

Although the technology behind the device is advanced, Apogee MQ-500 is very easy to use.

Apogee MQ-500 PAR Meter is high-priced. So, at first, you may hesitate to buy it. But, this device will allow you to take indoor growing to the next level and maximize your yield.

Many indoor growers who purchased this device will tell you that having a PPFD meter is priceless, because it will eventually give you more control over your plants’ growth.

How to Use a PPFD Meter With Your Plants?

Using a PPFD meter, you can take several PPFD measurements around the plant canopy.

You should cover all the growing area with the meter, then note down the measurements in a chart like the one shown below.

PPFD light meter for plants measurments

How to Understand PAR Readings?

The PPFD measurements will allow you to choose the plants you can grow under a light fixture.

If you plan on turning on your grow light for around 14 hours a day, the most light-demanding plants will need a maximum of 700 μmol/m²/s to flourish, while medium-light ones will thrive on 300 μmol/m²/s.

Constantly measure your PPFD values at different distances between the plants and the grow light so you can decide when to raise your fixture as your plants grow taller.

The PPFD values also show the discrepancy in PAR between the center and the sides of the coverage area. This will allow you to assess the uniformity of a grow light.

If the light is uniform and intense, you can grow a combination of full sun plants all over the growing area.

However, if PPFD values of your light vary significantly around its coverage area, you might have reduced yield in the plants growing at the sides.

Summary & Conclusion

Measuring light for plants is a brilliant way to optimize indoor growing, and there are two ways to do that.

You can either measure the intensity of light in terms of lux or measure both its intensity and quality in terms of PPF and PPFD.

Therefore, to measure light you need a lux or PPFD meter.

light meter for plants

Lux meters will measure the intensity of light in terms of lux. You can use them to take readings of sunlight, or when you want to just estimate the intensity of a grow lamp.

The best lux meter on the market is Dr.meter 1330B.

To evaluate the quality of light, however, you must use a PPFD meter. The best PPFD meter is Apogee MQ-500 PAR Meter.

Apogee MQ-500 PAR Meter is expensive, but it’s very useful for professional indoor gardeners. It allows them to have a full assessment of the quality of artificial light and its intensity.

Enjoy gardening indoors and don’t forget to share your thoughts in the comments below! 

Illustration Credits:
Gardening Vectors by Vecteezy
Light Meter Vectors by Vecteezy

Blogger, Gardener | + posts

I'm Jad, a biologist, blogger, and experienced indoor gardener. I am knowledgeable in plant biology, particularly in plant cultivation and propagation. I founded HerbsWithin.com in 2019 to share my knowledge in indoor gardening with passionate home growers.

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