Grow Lights Part 1: A few grow lights I’ve used

In this article, I’ll show you 4 grow lights I have personally used with satisfactory results. I’ll share my thoughts on what makes them a good choice, which plants would benefit from them, but also why you might look for an alternative.

Disclaimer: this article contains affiliate links from Amazon. A portion of sales goes to support the work of House Plant Journal. I’m also pleased to present some brand partners who I’ve selected because I’ve been very happy with their products. The SANSI 70W Daylight LED Grow Light was generously provided by Sansi. The Aspect grow light is from Soltech Solutions.

But to start, let me do the “light meter” rant:

My trusted light meter - get it here:  https://amzn.to/2OTIRaL
My trusted light meter – get it here: https://amzn.to/2OTIRaL

If you’re confused about how to choose a grow light, it’s because the manufacturers are throwing lots of specifications at you AND trying to get you to understand what they mean AND trying to convince you of what’s important…the burden shouldn’t be completely on them!

Do yourself a favor and get a light meter (measuring lux or foot-candles), otherwise you won’t have any concrete way to even roughly* compare your natural light with the strength of a grow light. It would be like buying an oven and not being able to set a specific temperature – guessing won’t cut it!

*I say “roughly” because light from the sun is different from all artificial sources when you look at their spectral distribution – that’s for another blog post! For now, if you’re just growing plants for fun, being able to measure lux/fc will suffice – it’s WAY better than trying to judge with only your eyes!

The Sekonic Spectromaster C-700: seeing light like never before!

The Spectromaster C-700 is a handheld spectrometer - here I’m measuring sunlight. Notice the SHAPE of the spectral distribution: sunlight is evenly distributed across the wavelength range. I’ll do a separate blog post where I find the spectral distributions of all kinds of lights - it was really fun!
The Spectromaster C-700 is a handheld spectrometer – here I’m measuring sunlight. Notice the SHAPE of the spectral distribution: sunlight is evenly distributed across the wavelength range. I’ll do a separate blog post where I find the spectral distributions of all kinds of lights – it was really fun!

In order to really see what’s inside the light, my friends at Soltech Solutions let me borrow their Spectromaster C-700, which is normally used by the film industry to get very precise color information about any light source. I’ve been having a blast analyzing the spectral distribution all kinds of light sources – I’ll do a separate blog post on it!

While I can already hear the horticulturalists saying “you should be using a PAR meter!” – you don’t get to see the spectral character of the light with a quantum meter. So for this article, I’ll just use the Spectromaster C-700 to measure foot-candles and spectral distribution.


Adjustable Blue/Red Grow Light: https://amzn.to/2L4E8lw

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Why only blue and red LEDs? (I’m going to write a more complete blog post on light spectrum but for now, here’s a quick answer)

Research showed this:

Chlorophyll a and b absorb most efficiently in the blue and red areas of the spectrum so some grow light manufacturers decided to ONLY make LEDs in those colors. Problem: green light is still used by plants even if it's not the most efficient driver of photosynthesis for chlorophyll - plants growing under a forest canopy use LOTS of green light.  Source:  https://en.wikipedia.org/wiki/Chlorophyll
Chlorophyll a and b absorb most efficiently in the blue and red areas of the spectrum so some grow light manufacturers decided to ONLY make LEDs in those colors. Problem: green light is still used by plants even if it’s not the most efficient driver of photosynthesis for chlorophyll – plants growing under a forest canopy use LOTS of green light.Source: https://en.wikipedia.org/wiki/Chlorophyll

I’ve used this type of grow light to successfully grow ferns in my shower (full article HERE). Notice how close the grow lights are to the plants – this is pretty much how close they need to be in order to be useful – at this distance, I’ve measured 200-300 foot-candles but it probably works out to a higher PAR due to the low sensitivity of the light meter to red light (more on that HERE). Once you’re farther than say, 12 inches, the grow light would only be useful for a “low light” plant like pothos. Also notice that I have 5 LED strips (2-head + 3-head) in order to cover the amount of foliage of these two fern planters.

I turn them on when I go to bed and turn them off when I wake up. The pinkish glow is effectively a night-light!

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Thoughts: if you don’t mind the pinkish glow, then a few of your very small, low-light plants would benefit from having them on this winter like small ferns, pothos, philodendrons, zz plant – I stress *small* because the coverage of these lights is very limited. Don’t expect to light anything in a 6″ pot or larger. And if your plant requires direct sun, skip this light – it’s much too weak!

T5 LED Lights: https://amzn.to/2KYWPHh

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I have 2 of these hanging above my couch to light the plants on my grid wall. Since these lights have a pleasant white color (I got the 5000K version), they are more suitable to also light up my living room. With two lights, I measure 700-800 fc quite close to the lights (about 6-12 inches below); farther away, I’m getting 200-300 fc at the lowest part of the shelf. I’m quite happy with the coverage all around the shelf.

LED lights emit smoothly across the 400-700 nm range (the PAR range) with a spike at the blue region. Take note in the red area: 660-700 nm range, it's 20% (0.2) as strong as the blue area (1.0).
LED lights emit smoothly across the 400-700 nm range (the PAR range) with a spike at the blue region. Take note in the red area: 660-700 nm range, it’s 20% (0.2) as strong as the blue area (1.0).

Thoughts: the lights come with mouting brackets that you’ll need to screw into the surface where you want to mount the lights. The fixture itself is quite minimal so the effect is like a bar of pure light, which could be cool if you’re going for that look. If you put your plants no more than 3-4 feet away from these lights, you’ll get good results for “bright indirect light” type of plants. You might be able to support a few sun lovers right up close to the lights or if you put 4 lights together.

SANSI 70W Daylight LED Grow Light: https://amzn.to/34qS1lD

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This array of LED lights by SANSI measured in at over 3000 foot-candles about 1 foot away. At this intensity, you could keep succulents and cacti quite happy if you ran the grow light on for about 12 hours. Further away, even though the intensity is much less (300-500 fc at 4 feet away), your coverage area is wider – you could use this as a supplemental light by turning it on say, at 4pm and off at 9pm (5 hours), which would be an excellent boost for most tropical foliage plants.

The blue region is again the strongest color on the spectrum but the red region (660-700 nm) is up closer to 50% (0.5).
The blue region is again the strongest color on the spectrum but the red region (660-700 nm) is up closer to 50% (0.5).

Thoughts: I’m a fan of mounting options – the SANSI 70W LED comes with hardware to mount the panel in several differt ways: suspended by an adjustable wire or mounted directly into an overhead surface. The look is rather utilitarian, which would be fine in a grow space in your basement but may not look as nice in the living room. Overall, this is a very powerful grow light at a good price.

Soltech Solutions Large Aspect White (also comes in Black)

Get the Aspect HERE

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The first thing to note is the elegant design! Both the black and white versions blend in nicely to most interior themes, which means you can keep a plant alive and well anywhere indoors. The other thing that struck me was the power of this light – it’s the most powerful consumer-focused grow light I have ever measured. At one foot away from the light, I measured over 8000 fc – but you definitely should NOT use it this close to a plant (there must be good air flow around the fixture so heat can dissipate – this applies to all grow lights). Using this light at 4 feet away, I measured 500-800 fc, which would make most “bright indirect light” plants very happy. If you had a small collection of cacti and succulents, putting the large Aspect 2-3 feet away would be a great light boost during the winter months.

The color temperature of a light affects how we perceive its "warmth". Counter-intuitively, a cooler, blueish light is a higher color temperature: 6500K is a very blueish white, 5000K is close to daylight, 3000K is a warm yellowish glow. The Aspect is near 3000K, which corresponds to a higher proportion of red/orange compared to blue. If we look closely at the blue region (near 0.5) and the red region (also near 0.5), the ratio is nearly 1:1. This got me to researching red/blue color ratios for grow lights but most data pertains to lettuce growth, which suggests higher red for more leaf surface area. As a general rule, higher blue light promotes short, stocky growth while higher red light promotes longer, bigger leaf growth - assuming equal light intensity.
The color temperature of a light affects how we perceive its “warmth”. Counter-intuitively, a cooler, blueish light is a higher color temperature: 6500K is a very blueish white, 5000K is close to daylight, 3000K is a warm yellowish glow. The Aspect is near 3000K, which corresponds to a higher proportion of red/orange compared to blue. If we look closely at the blue region (near 0.5) and the red region (also near 0.5), the ratio is nearly 1:1. This got me to researching red/blue color ratios for grow lights but most data pertains to lettuce growth, which suggests higher red for more leaf surface area. As a general rule, higher blue light promotes short, stocky growth while higher red light promotes longer, bigger leaf growth – assuming equal light intensity.

Thoughts: because the Aspect turns on immediately when plugged in (i.e. there is no switch on the fixture), you should use it with a timer, which is included. Soltech Solutions also includes some mounting hardware that allows you to run the wire against the wall and over the ceiling above your plants. If you’re looking for a very powerful grow light that you can proudly display in your living room, the Aspect is an elegant solution.Soltech Solutions has a handy page with lighting guidelines for many popular houseplants – HERE

Here’s my list of common houseplants and their light requirements – WITH NUMBERS!

In Part 2, I’ll use the latest version of Apogee’s full spectrum quantum sensor (an early Christmas present to myself!) to make some super accurate measurements and we’ll discuss how this relates to DLI (Daily Light Integral).

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10 responses to “Grow Lights Part 1: A few grow lights I’ve used”

    • I said I turn on the lights over night but they are off during the day in a bathroom with no windows, so it is effectively dark for 12 hours.

  1. I just bought a Verilux light to use with my lithops and Pilea. I live in Northern CA, in an apartment with very low light. Just got your book from the library and found your blog, great info!

  2. Just wondering. I have a monstera adansonii on my landing. It’s growing, albeit slowly. But was considering changing the pendant light that is about 3 feet from it (it’s stored high up and trails down), to an LED chandelier. Would this work?!

    • You would need to measure it to know. As a very rough guideline, you would want to see 200-400 FC at the leaf location and keep the light on for about 12 hours a day.

  3. Hi there! I was considering placing LED grow light strips on the underside of some built in shelving. This would be anywhere from 3-6 inches away from the plants? Do you think that’s too close? They’re similar to the red/blue clamp on lights you have in this post?

    Thanks!

  4. Hello! Wondering. about the grow light strips. I was thinking of using them inside a glass cabinet – i’d probably need 2ft ones. Does it matter if it’s t5 or t8? I seem to only get t8 options

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