House Plant Grow Lights – Everything You Ever Wanted to Know

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Ok, so it might not be everything YOU want to know about grow lights, but it’s definitely everything I wanted to know before, er, I knew it.

Grow lights can be a very confusing topic. There’s a lot of information about wattage and colour spectrum etc etc etc when all I wanted to know was which grow lights actually worked, how long I needed to leave them on for, and how much they’d initially cost and cost to run.

Hopefully I cover everything here, but feel free to leave me a comment asking any questions and I’ll do my best to find the answer.

Anyway, let’s crack on.

Should I use a grow light for my indoor plants?

I would get grow lights if:

  • If you live somewhere that has ok light all year round, then you may not need grow lights. But if you live in colder parts of the Northern hemisphere, they may help a lot.
  • Do you have a lot of plants? If so, and you find that they suffer from lack of light in the winter, it might actually be more cost-effective to buy grow lights than it is to replace your plants.
  • This is even more the case if you have rare/expensive plants. Or if you get anxiety when your plants die, or you have plants that have sentimental value.
  • You have a dark area in your home that you want to put a plant in. Grow lights can make this happen. Just check there’s an outlet nearby first. My house has (literally) 30 outlets downstairs and two (2) upstairs.
  • You love propagating/ want to get better at it. Whilst natural light is always best (it’s free for a start) it isn’t a guarantee (cries in UK). Light is instrumental to root growth and having a back up is useful if the sun has fucked off.

I wouldn’t get grow lights if:

  • You can’t afford it. They’re awesome to have, but not necessary. I’ve made it through a winter without grow lights and I didn’t lose any plants. You can always trim back stunted growth in the summer.
  • You don’t have many plants. Effective grow lights (especially aesthetically pleasing ones) can be pricy, and if they’re more expensive than replacing your plant, you might want to consider whether or not they’re worth it

Can any light be a grow light?

I have a whole article here on whether plants will grow under normal LED lights, and answer is yes, but not as well as they would under actual grow lights.

Lights that are designed for the purpose of allowing humans to see in the dark don’t have the same spectrum as lights designed to help plants grow.

monstera leaf

Are grow lights effective?

Yes. Even the cheap grow lights I’ve found on Amazon do a stellar job at not letting my plants die over window, even though they’re in the dark recessed corner of an east-facing window.

You don’t need to spend a lot of money on grow lights if all you want in terms of results is for your plants not to die.

If you choose your plants carefully (for example plants like calathea and peace lilies) you can even encourage growth all year round, though it’ll probably be a little small and stunted.

But for those of you with loftier goals, such as preventing Alocasia going into dormancy, or even encouraging healthy growth in winter, you can get grow lights that will 100% deliver that.

I know, because I have some. My boyfriend gave me some of his old aquarium lights and I am SUPER impressed with the results I’ve gotten from them (yes, there will be a mini review further on).

monstera leaf

Are grow lights expensive to run?

I can’t give you ‘X grow light will cost X dollars per month to run’ because there are too many variables.

But I can tell you that over the course of the past 15 years, we’ve had everything from 0 grow lights running to upwards of 10 running (as well as aquarium heaters, filters, protein skimmers, and various other fish paraphenalia) and whilst we’ve seen fluctuations in our electricity bill, never anything particularly extortionate or out of the ordinary.

Grow lights typically use LED bulbs, are are pretty efficient to run.

monstera leaf

How long should you leave grow lights on for?

In an ideal world, you’d have your plants on a 15 hour on/9 hour off cycle.

I don’t do that.

My grow lights are usually on for around eight hours a day. I would probably get better results if I left them on for longer, but I get decent growth from 8 hours of light so any more seems a bit wasteful.

In the summer I move my light-loving plants closer to the windows, or even outside. In the winter they go under the grow lights. If you have to keep your plants in fairly dark places even in summer, then you could increase the amount of time the lights are on for, to better replicate the outside world.

Even if I can provide enough light for my plants in winter, it’s naturally less humid and it’s colder in winter, and I don’t want my plants to overexert themselves.

Bear in mind that there definitely is a maximum amount of light for plants. The 15 hour ideal is based off the natural light cycle in the rainforests that most tropical plants hail from.

You can’t hack the system by leaving grow lights on for 24 hours a day, because plants need a rest. Too much light can mess up their respiratory systems.

monstera leaf

How close to grow lights do plants need to be?

I can’t find a definitive answer on this, but too close and your plants will burn (no closer than three inches, but different plants burn at different rates) and too far away and they won’t get much benefit.

My lights are attached to my plant shelf, and I keep the plants that like the most light closest, and then rotate the others whenever (weekly/whenever I dust/they look sad) I feel they need it.

One thing that is, unfortunately, not possible is putting a grow bulb in your overhead light fixture and expecting that to provided enough light to stimulate growth in your plants. I’m afraid that’s too far away.

monstera leaf

Can grow lights burn plants?

Yes, but they have to be pretty close. My Monstera peru loves to get all up in my grow lights business so consequently almost always has at least one burn. The enormous peace lily that I have growing in the aquarium does get burned leaves, but there’s a not a lot I can do about it because it grew so big so quickly it grew kind of around the aquarium light.

It’s since been raised up and seems happier.

In my experience, plants burned by grow lights don’t seem as badly affected by it as plants that are burned by the sun. Sure, the leaf has a black mark on it (and nothing’s gonna change that), but the rest of the plant is unaffected.

LED grow lights don’t throw out a lot of heat, and any they do have is pretty directional, so you plant would have to be pretty close to cause a burn.

The sun, on the other hand, is pretty hot (you can count on me to provide all the facts) and can burn the leaves, suck all the water out of the soil, and even heat the soil to the point where it damages the roots.

So if you leave a plant out in the garden it could die in an afternoon, but a grow light will likely only do cosmetic damage UNLESS you have a mega powerful one.

I can only vouch for the grow lights I’ve used, so if any ones used one that’s burned their plants to dust, name and shame in the comments, please.

Are purple grow lights better than white ones?

This is where it all gets a bit technical for me, so I shall provide a link here to an article that explains all about purple grow lights.

In short, it seems that manufacturers claimed that plants could only photosynthesise red and blue light, so a full white spectrum was a waste of light. Turns out that red and blue diodes are cheaper, and plants love a full spectrum.

Do purple lights work? Yeah – plants use blue and red light the most. But if you don’t like purple light, a full-spectrum white light is just as good.

Which grow lights should I get?

My favourite grow light

The Fluval COB LED lamp is my favourite grow light. It’s not too big, looks like a normal light, and my plants grow year-round. It’s so so good. My hoya freaking LOVE it, and my Pothos don’t know that it’s winter.

They’re not on in the photo on the left because my boyfriend puts everything on timers – mostly for the terrarium you can just see on the shelf below.

Pros of the Fluval COB

  • Cheap to run – we have four and there was no difference in our electricity bill.
  • They’re bright but face down (since they’re aquarium lights) so they’re not blinding
  • They’re compact, so blend into shelving units well
  • They work. Pretty much all I’m looking for in a grow light.
  • They last. They have a bulb life of 50,000 hours, which is about 17 years if you have them on for 8 hours a day.
  • The light is white without being stark – it mimics natural light super well in terms of colour.

Cons of the Fluval COB

  • They’re designed for an aquarium, so the fixture is designed to clip on to the top of the tank. We ziptied them to the back of our shelving unit, but a command strip would probably work fine
  • They’re pricier than I would buy if I were a beginner. I stumbled across these because my boyfriend was using them for the fish and he got fancier ones and I inherited them.

The results were so good that I got more (ok, he bought me more). I mean, they’re not extortionate ($59.99), but if you’re forking out that much for a light you want to know it’ll work.

My budget grow light pick

The Relassy dual-head goose-neck growlight

There are loads of these cheaper options, and they do a decent job. Don’t expect a tone of growth, but they will give your plant enough light to stay alive.

cheap amazon grow light

Pros of the relassy grow light

  • Easy to clip on to shelving
  • Cheap and cheerful
  • They come with replaceable bulbs. The ‘how long do the bulbs last’ question is answered in the cons part
  • They do the job. Nothing startling, but my plants are alive
  • The goose neck designs means you can direct the light wherever you want. Extremely useful if you’re a winter jigsaw puzzler like me (or knitter or reader). I’d repurchase for this feature alone.

Cons of the Relassy grow light

  • Leaving the lights on for more than five hours can affect the longevity of the bulb. I leave mine on for longer, and so far the bulbs have lasted. I’ll update when I need to replace but so far (over a year) they’re fine
  • They come with a plug but the actual unit has a USB adaptor. And every time you slightly knock it the lights flicker – but only the tiniest amount so at first you don’t know what’s going on. Ghosts? Murderer? Who knows?. It’s a minor inconvenience but it can be annoying.
  • The light is quite warm. It doesn’t bother me, but I know some people don’t like it.

Regular lamps as grow lights

I have a lot of dark corners in my house, and a lot of plants. This lamp with a regular bulb (sorry, I’ve no clue what the wattage is, but it’s probably from Ikea) does a decent job of keeping my Philodendron Imperial red and Thaumatophyllum selloum alive. They don’t put out much growth, but they’re, you know, not dead.

lamp and house plants

Incidentally, that philodendron is in Leca, and converted like a freaking DREAM. It really makes watering easier in winter, The selloum had to live outside in the summer (thrips love him) but he’s been allowed back in for winter.

A wild card pick for best grow light

I recently got myself an Aerogarden (and my herbs are GROWING!) and it’s been a welcome source of additional light. My smaller succulent and African violet are enjoying the extra light, and whilst it was pricy, it’s a great multi-tasker if you’re looking to grow your own food or just give hydroponics a try.

aerogarden grow light

Final thoughts on grow lights for house plants

Are grow lights necessary to keep house plants alive. No. Unless you live in a cave, your plants will probably survive the winter. However, if you have a lot of plants and the thought of them struggling is anxiety-inducing, them a grow light is great for peace of mind.

You don’t need to shell out on fancy ones if you can’t afford it (or don’t want to). I probably wouldn’t have had my boyfriend not had spare ones (#perpetuallycheap), but I’m glad I had the opportunity to try them, because they’re awesome.

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