Adventures with Indoor Lighting:

Craig Sullivan
14 min readFeb 16, 2020

I hope this is a useful guide, not so much for being the most comprehensive but for just inspiring you to experiment and try out indoor plant lighting for yourself.

This technology is improving and iterating all the time, with miniaturisation, lower power consumption and cooler running coupled with better lighting density. In the last year (2019–2020), I’ve seen three iterations of LED tech appear and ripple into mass market products. It will only get better but already costs as little as, or less — than the same wattage incandescent bulb.

First of all, this article wouldn’t have been possible without James Wong, who has massively expanded the range of what people would even consider growing. I’m still in awe of his work and how simple and beautiful his art with plants is to my eye. Over all my years of reading and observing, travelling to gardens, looking at all styles and approaches to plants — there is only one person who ever showed me exactly what keeping plants was about — Kyuzo Murata ( https://www.magiminiland.org/KMurata.html) and his work can be summed up for me in this one picture:

Kyuzo Murata — Four Seasons of Bonsai

This is just a simple pot and arrangement and arrangement of lilies but it’s also one of the most beautiful things I have seen. Looking at his work, the penny finally dropped. That was when I understood that releasing the very habit and essence of the plant was the job of the artist — not to mold, cut, slice and snip like edward scissorhands but to step back and see the plant itself explain the nature of the sculpture you are about to assist.

James Wong has that touch in terms of seeing and bringing out the nature of plants in his work. Both Murata and Wong to me are masters.

I’ll write another piece about Murata and the concepts of Wabi and Sabi — but that’s for another day. It has taken me several years of thinking to even begin to understand my own particular connection with plants, nature, seasons and life itself but I hope to explain it in a way that gardeners and philosophers will enjoy.

James has written and shared a lot of useful info about lighting and he’s tried out a fair amount of lamp tech, starting with the Ikea kit. Let’s start at the beginning though — I’d like to give you some background, starting with the science, moving onto the kit and then giving you an options summary.

The Science Bit

This article wouldn’t have been possible without the information from these authors:

Robert Pavlis: https://www.gardenmyths.com/led-grow-lights-color-spectrum/

Kevin Espiritu: https://www.epicgardening.com/best-full-spectrum-led-grow-lights/

The Green Sunshine Company: https://thegreensunshineco.com/7-myths-led-grow-light-companies-tell-you/

I’ve been gardening for 30 years but initially struggled with houseplants, because the same approach didn’t work as well as outside. That’s because the variables of humidity, water, light and temperature are completely different indoors.

Plants don’t always want to be where you’d like them and so figuring out their needs for an indoor environment means a bit of experimentation is necessary. Don’t worry if you kill stuff — I do all the time, just in smaller quantities than I used to ;-)

You’ll end up moving plants around sometimes, just to find their ‘right place’ — where they seem to be happy. Sometimes, however, there just isn’t enough light in the ‘right place’ and this limits your options. No longer though!

With LED lights, we can expand the range of places and plants we can have inside our homes.

With indoor plant lighting (IPL) you can cover these scenarios:

You have a room with no windows or almost no light

You have low light or light for only a short part of the day

In winter, the light doesn’t seem enough for a plant that’s okay in summer

You want to grow seedlings for later planting but don’t have enough light

You want to move a plant, but worry it won’t get enough light

You’d light to make a light sculpture, box, growing rig or water feature

You want to grow micro-greens or herbs indoors

So let’s start with the science bit then:

Wavelengths

All light that we (and plants) can receive from the sun, is made of up different wavelengths or ‘colours’ of light. Those wavelengths turn out to be pretty important for growing things indoors.

If you look up at the sky, that big fireball keeping us warm is a pretty good guide to what plants need. What spectrum does the sun kick out?

As you can see, it’s a whole range of colour wavelengths. Whilst it’s true that plants can use some of the wavelengths that people can’t see, that’s not where most of the action is. Fortunately, science has worked out exactly what spectrum is absorbed by plants. Take a look at this diagram:

To absorb this light, plants have a primitive but very effective version of our eyes, which we call pigments in plants. The most commonly known one is chlorophyll and it is used to capture mainly red and blue light on the graph above. There are also other pigments including carotenes and xanthophylls which harvest light in other wavelengths and pass it on to the process of photosynthesis.

The Response Spectrum Trick

That explanation was important, because you’ll see products for sale that use red and blue LED lights, where claims are made about what plants need.

You’ll see a diagram a bit like this, showing the peak response spectrum for Chlorophyll A and B:

The problem with this, as we showed earlier, is that plants need more than just these spectrum peaks for one or two pigments. It’s a lot more complicated than that. Whilst the diagram is correct, it’s trying to trick you into thinking the lights are a perfect fit for a plant, when it’s not ideal.

This is the number one weakness of products that use RED/BLUE lights. They are good at growing seedlings and producing short compact growth (they’re pretty good for growing succulents indoors, for example) and also will drive flowering nicely. However, these lights are missing a lot of the green and yellow spectrum that plants ideally need. You can’t take these RED/BLUE lights and use them with houseplants, because they’re simply not full spectrum enough. The other problem is that the spectrum of light they do kick out does not penetrate deeply into the canopy of leaves you are lighting.

So trick #1 when selling you a light is to insist that RED/BLUE will work okay for your houseplants. No.

Let’s move onto claim number 2:

Full Spectrum Lighting

This is often just a claim. If someone is selling a blue/purple LED light or strip of these — as ‘full spectrum’ — then you should know this is a lie. You need a mixture of different LED colours to make up a ‘full spectrum’ and whilst some high end equipment does this nicely, the consumer kit that claims to be full spectrum should not have blue/red lights.

The entire industry is now moving towards offering products with true full spectrum, rather than a mix of different coloured LEDs. This isn’t about matching the ‘colour of the sun’ or ‘white light’ — it’s just that these bulbs offer a mixture, so you get lots of blue and red, some green and yellow, some infrared and near UV too. Plants need a mixture of wavelengths (some more for particular stages of growing).

I’ve got some genuine products and bulbs below that feature the latest technology. What they’ve done is to combine a blue LED with a drop of phosphor coating. When the blue LED emits light, the outer phosphor coating emits white light at a specific colour temperature that’s controlled by the blue light wavelength and composition (doping) of the phosphor layer.

Sorry for all the science but it’s useful to explain this difference. These new lights have a super long life and offer excellent growing results, so it’s worth buying the latest tech!

PAR & Lumens

You’ll often see these terms bandied around enthusiastically. PAR basically means ‘visible spectrum’ and Lumens isn’t really the right measurement for plants. If a light says it covers a full PAR range, then it’s referring to being a full spectrum light essentially.

Wattage

When you are looking at the power draw of a light, most of them are pretty close to the rating. If you have a 40W LED full spectrum light, it’s the same power draw as a 40W bulb. The cost of running this stuff is pretty low and I’ve had NO failures of any LED lights, even after 3 years of usage. That’s pretty good going and spreads my outlay over several years.

Types of Light

So now we’ve done the science bit, let’s show you examples and links to the different types of light. We’re going to cover the following:

Daylight bulbs

LED bulbs

LED mega bulbs

LED light bars

LED panels

LED strips

CF Rigs

Daylight Bulbs:

These are basically a special type of lightbulb — either a spiral tube (CFL) or an LED — that offers a light spectrum of around 6000–6500K. These are a nice cheap option, since they are just a standard light fitting and bulb.

The first type uses a spiral tube and is called a flourescent or CFL light. They look like this:

You can either get these as strip tubes or twisted into a lamp shape like the picture above. If you specify the right colour temperature (6000–6500K) and the light output is high enough (opt for a high wattage) then these will give you a cool running but good light. CFs like these are slightly less expensive than LED technology but don’t last as long.

As long as you don’t mind the cooler light these kick out, you can use them in windowless rooms, alcoves, as a topup light for a plant in a darker spot.

Have a look at these on Amazon:

https://www.amazon.co.uk/s?k=compact+fluorescent+grow+light

https://www.amazon.co.uk/Ecozone-Energy-Saving-Daylight-Equivalent-Spectrum/dp/B000F6Z4EG/ref=sr_1_12?keywords=full+spectrum+led+bulb&qid=1581861300&sr=8-12

The second variant of these bulbs uses LED technology, just in a standard fitting wrapped in a bulb shape, like this philips 6500K LED bulb:

Take a look here on Amazon:

https://www.amazon.co.uk/s?k=full+spectrum+led+bulb

These bulbs aren’t bad but the intensity of the power they kick out is usually not enough for more than 1, maybe 2 small plants. The CF bulbs run really cold, so you can get them closer to the plants and their spread of lighting is usually wider.

So you can buy some low cost bulbs for 3/4 quid and use these for lighting dark spots — here’s one example of a bulk buy on Amazon:
https://www.amazon.co.uk/LVWIT-Bayonet-Daylight-Equivalent-Non-Dimmable/dp/B07JM14XDF

LED Grow Bulbs:

These are just straight replacements for bayonet or screw fix lights — so you can plug them into existing lights or run your own cabling. These lights will usually have metal fins, a headshell or panels to dissipate heat — so that should be a clue to you that they can run hot. Warning!

They are never as hot as incandescent bulbs in the same place but you still need to be careful these don’t touch the plants or furnishings. If you use them in an enclosed space like an alcove, cupboard or shelf — you need to have ventilation for the heat to escape. I’m not being a killjoy here — I’ve never had any sizzled plants or furniture because I’ve been careful!

Here are some example red/blue bulbs from Amazon:

https://www.amazon.co.uk/Spectrum-Lighting-Vegetables-Greenhouse-Hydroponic/dp/B07QCRZW23/ref=sr_1_10?keywords=led+grow+bulb&qid=1581861804&sr=8-10

https://www.amazon.co.uk/Spectrum-Greenhouse-Hydroponic-Growing-85-265V/dp/B07CRG1SQP/ref=sr_1_24?keywords=led+grow+bulb&qid=1581861804&sr=8-24

Here are some full spectrum lights from Amazon:

https://www.amazon.co.uk/Spectrum-MILYN-Hydroponic-Greenhouse-Succulents/dp/B07PNG5FD2/ref=sr_1_9?keywords=led+grow+bulb&qid=1581861804&sr=8-9

https://www.amazon.co.uk/MILYN-Flowering-Hydroponic-Greenhouse-Succulents/dp/B07MM8N6BP/ref=sr_1_2?keywords=led+grow+bulb&qid=1581861804&sr=8-2

WHERE TO USE

Use where you want to repurpose a light fitting to be a plant light

PROS

Easy to fit to existing bulb sockets

CONS

Light is usually a limited angle or direction

Will only light one or two houseplants

Can’t be used at a large distance

Won’t easily scale up

LED Stalks:

These are just either single flexible stalks (with one bulb) or multi headed bulbs where you have 2–3 heads. Most of them come with clips or mounting kits for shelves or other locations and look like this:

These are an excellent purchase, particularly the full-spectrum bulbs, as they can cover a pretty large area. If you move plants around, you can adjust the lighting as you go.

Same stuff applies as for LED bulbs — these usually have fins, heatsinks or other stuff that will run hot, so be careful where you place the bulb heads.Some of the models have rubbish flexi-hoses — so that they don’t hold their position. Don’t leave a light where it could sag and then rest on something!

Try to buy these where the bulb can be replaced. All in one units might be cheaper but they’re aren’t as easy to maintain. If you’re going to own the lights for 5 years, make sure you can replace a bulb if you’re unlucky enough to get one or more heads that fail.

Here are some 1,2 and 3 stalk lights from Amazon — I’ve not included any RED/BLUE lights here, because this kit is way better:

https://www.amazon.co.uk/Spectrum-Stepless-Adjusted-Gooseneck-Replaceable/dp/B07YS9SJ8M/

https://www.amazon.co.uk/Spectrum-Gooseneck-Replaceable-Seedling-Blooming/dp/B07NYPGPP7/

https://www.amazon.co.uk/Relassy-Spectrum-Function-Dimmable-Sunlike/dp/B07J65WMQR/

Replacement bulbs are available, like these for most models above:

https://www.amazon.co.uk/Bonlux-Lights-Spectrum-Rotated-Convertible/dp/B07W9KKBRK/

https://www.amazon.co.uk/Replaceable-Sunlike-Spectrum-Seedling-Fruiting/dp/B07RP6LM6G

WHERE TO USE

Use for shelves, alcoves, windowsills and groups of plants

PROS

Useful, flexible and cheaper than multiple bulbs — covers a larger area (4–8 plants)

Can adjust lighting direction or position easily

Easy to replace broken bulbs

CONS

None really — it can look messy if you try to use lots of lighting heads.

LED Light Bars:

These are great for shelving, recessed areas or where you’ve got somewhere you can hang a light above plants. They’re usually made out of aluminium and come with hanging kits and clips. The kit I’ve bought is also moderately splash proof, which helps with the odd bit of spilled water.

These aren’t yet available in full spectrum variants, so these are the only red/blue ones that are decent:

https://www.amazon.co.uk/Function-Anywhere-Charging-Horticultural-Growing/dp/B07GB28WCH/

https://www.amazon.co.uk/dp/B00YTWMSN2/

https://www.amazon.co.uk/JCBritw-Indoor-Hydroponics-Greenhouse-Seedlings/dp/B076HNRNZ4/

WHERE TO USE

Use for shelves, alcoves, anywhere you can hang a light above the plants.

PROS

Covers a wide/long area of plants

Tough construction and DIY approach means these are easy to install

CONS

Although these cover a long run, they won’t cover a wide area with high intensity. This is because the angle of light isn’t 180 degrees, it’s more like 45 degrees either side of vertical, so it won’t do a long and very wide plant shelf, for example. You may need to mount two in parallel.

LED Panels:

Strip lights usually have a long row of LEDs so these panels just extend this to make a square or rectangular array of lights. If you want to cover an area that’s more square or round than a strip will cover, these are for you:

They’re also good for under shelving and have a good angle as light scatters quite well. I have shelves where I hang these above and they cover nearly twice their area on the shelf below.

These are usually aluminium and plastic and kick out a fair bit of warmth. You either have to suspend them (they come with clips or wires) or mount them with space for ventilation. The temperature isn’t going to burn you — don’t worry. I just don’t like things kicking out heat if the heat can’t escape.

Here are some examples from Amazon:

https://www.amazon.co.uk/Bozily-Spectrum-Foldable-Germination-Flowering/dp/B07L57Z5TP/

https://www.amazon.co.uk/gp/product/B07QVGNGM8/

WHERE TO USE

Use for shelves, alcoves, anywhere you can hang a light above the plants.

PROS

Covers plant arrangements that are either wider, rounder or need a larger area cover than strip or bulb lighting

Easy to install

CONS

None really — the growth using these has been awesome, way better than the strip lighting I had before.

LED Flexi-strip:

I include this here simply because it’s so flexible. Imagine a strip of LED lighting that is bendable and can be run underneath things, round corners or enclosing plant containers and furniture. Right now (as of Feb 2020) I can’t source any full spectrum version of this but you can get the RED/BLUE version. In a few months, the newer tech should be available.

All you need to do is cut the flexi-strip to size and then connect it to a little power adapter. All you need are scissors. The flexi strip has adhesive, so you can glue it onto surfaces after cleaning them.

Here’s some example flexi strip kits from Amazon:

https://www.amazon.co.uk/dp/B06W9LS8XP/

WHERE TO USE

Too hard to fit other tech

PROS

Easy to install, cut to size

CONS

Not high power — so it won’t cover a great distance (a few cm I think). Don’t expect this to light large amounts of plants but it’s good for supplementing existing lighting or reaching hard places. No full spectrum available (yet).

CF RIG

Most of the LED bulbs I’ve shown you here are rated around 50,000 hours. In 3 years of growing, I’ve lost two cheap bulbs. None of the LED strips, light bars or panels has had a single failure or problem.

I still have an application for old tech though. If you want to grow seeds or salad veg, you need an adjustable light rig, where you can vary the height as things grow. Established and slower growing plants are different:

Right now, I can’t get one of these with good enough full spectrum LED lights. However, they do make one of these using CF (Flourescent) lights (pictured above).

The tradeoff here is the lightbulb only lasts around 10,000 hours — not as long as the LED technology. By the time the bulbs finally go, I should be able to retrofit a new full spectrum LED as it will be available on the market by then.

Here is the rig I’m using for seeds this year:

https://www.amazon.co.uk/gp/product/B0038NDWME/

Summary

I hope the main thing you’ve discovered is that you CAN buy some decent kit, without being ripped off.

The lighting technology is improving every few months but if you are aware of what’s crap, you can have low cost and long lasting growing kit right now — that you’ll still be using years later.

I’ve been growing about 40-odd plants using a mixture of lighting strips and bulbs — the full spectrum stuff works so much better, that I’m replacing all the RED/BLUE lights as new versions become available.

Have fun bringing a little sunshine into your house. One big benefit of the full spectrum lights over the RED/BLUE is that your neighbours no longer think your window onto the street looks like it’s in the red light district ;-)

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Craig Sullivan

Conversion Optimisation, Usability, Split Testing, Lean, Agile,User Experience, Performance, Web Analytics, Conversion Optimization ,#CRO http://t.co/BSWwzHj00S