This article stands alone in a mass of ‘this plant can survive in zero light!!’ posts that are not exactly lying, but are not looking out for the plant’s best interest.
I don’t want this post to discourage you from keeping plants in low light, I just want to tell you what the situation is.
Now, I am not a botanist or a biologist so what I’m about to say is very much in layman’s terms:
Light is as important to plants as food is to you and plays *broadly* the same role in its life.
- ALL plants need light to survive. The amount varies by species
- Most plants can tolerate low light levels for a time – again, the length of time varies by species
- You can’t replace light with anything. Watering a plant perfectly won’t help, just like a human can’t survive on water alone. They can survive for longer without food than water, but not indefinitely.
If you’re wondering where fertilising/soil fits into this, think about it like this:
Humans can survive perfectly well on a very limited diet. VERY limited. However in order to thrive and live a life free of disease we need a balanced diet that contains all the vitamins and minerals we need. soil and/or fertilising plants makes sure they have a balanced diet.
This actually isn’t that important for houseplants, 1. because soil/ water alone as a substrate usually provide ample nutrients for foliage growth and 2. there isn’t enough research done into houseplants to know what fertiliser is best for what species.
However, if you’re growing plants for their fruits (like tomatoes) they need a fertiliser to ensure they grow optimally (luckily there’s been a tonne of research done into getting tomotoes to grow well).
House plant beginner? Avoid true low light houseplants
If you don’t think any of these reasons are going to be a problem for you, fine BUT plants that live in low light conditions in the wild tend to be pretty picky when it comes to other aspects of their care:
- Houseplants that live in low light places in the wild also need high humidity. They are likely to grow on rainforest floors where the humidity rarely dips below 60%.
- They will not tolerate drying out. There are three ways this plays out
- Plants like fittonia that droop but can be revived after a drink
- Plants like maidenhair ferns – their fronds will crisp up and won’t be salvageable but the roots will be fine (for a time anyway) and new fiddleheads will grow
- Plants like calathea that will straight up perish. The smaller they are the less time this will take.
- Houseplants that live in low light places in the wild are WAY less tolerant of impure water. Common plants like fittonia have been cultivated for years so they’ve been bred to be more tolerant of tap water but if you fancy something rarer be prepared to fork out for filtered water.
- They need to stay warm. Again, there are exceptions to this rule (a lot of ferns, for example are cold-tolerant) and you’re usually ok with common varieties. Except calathea. Any drop in temperature and the spider mites move in
Plants that live in naturally low light conditions like consistency of water, humidity, light and temperature. That can be difficult to provide if you live somewhere as far north of the equator as Europe and much of North America.
Why new houseplant people should aim to maximise the light their plants are getting
Light is BY FAR the thing that will keep your plant healthy. It’s like a cheat code. I’m not exaggerating. If you’re having issues with your plant and you don’t know why, try giving it more light.
I won’t yap on about bright indirect light because it isn’t helpful. Light varies a lot depending on where you live.
What the vast majority of plants want is LONG hours of ok light. I go into this more in this article about grow lights for Monstera.
Long hours of ok light will suit most houseplants. Calathea prefer medium light, ficus brighter, but they’ll both do totally fine in ok light.
So what is ok light?
Somewhere that you could read (or do a jigsaw, or knit or something) without having to turn on a light.
The exception here is cacti and succulents, who don’t want consistency or humidity. They want the sun beating down on them all day, half an hour of HEAVY rain, zero humidity and a cold-ass night.
Each to their own.
9 signs your plant isn’t getting enough light
1. The plant isn’t growing
Plants need to light to grow. There are, of course, other reasons why your plant isn’t growing. If you have a Monstera Thai Constellation, for example, they simply don’t like to grow!
But lack of light is a likely cause.
2. Your plant can’t shake pests
This is SO underestimated. Ok, so I’m not saying that plants that get enough light are pest resistant OR that increasing light can shake an infestation BUT plants that get enough light aren’t as interesting to pests as sickly ones that are kept in a dark corner. Plants kept in lower light have thinner leaves (I assume to help with light absorption).
3. It’s producing leggy growth
If the internodal spacing is long and your plant is looking droopy, lack of light is a likely cause
4. All the new growth is small
2 things increase leaf size significantly:
- Growing the plant up something (if it’s a climber)
- Increasing the light
Pothos are frequently touted as a low light loving plants. They can survive it, sure, because those plants are survivors, but look at this regular golden pothos (devil’s ivy if you prefer) at my local garden centre:
This has nothing to do with nutrition or special growing techniques. This is light and something for it to grow up (anything – plank of wood, moss pole…attach it to a wall with hooks if you like.
5. The soil stays damp for weeks
More light does mean more watering unfortunately BUT it does mean that the soil dries out quickly and you’re less likely to get root rot. If your soil is staying damp for weeks then that’s a pretty damning sign that your plant isn’t getting enough light.
NB this doesn’t apply to plants that NEED to be damp all the time, like fittonia and maidenhair ferns.
6. The leaves are pale or yellowing but the roots are fine
Yellow leaves often has people screaming ROOT ROT (ok, not actually, but let’s imagine it does) but then you go and check the roots and they’re…fine. Could be lack of light. There are ways of keeping roots healthy in dark spots (like having a very well-draining soil) but the leaves won’t be able to flourish.
7. It’s stretching towards the window
Most plants will grow towards a light source – no matter how much light it gets. It’s the stretching that’s the issue. Look up etiolation. It’s trying to grow towards the light because it’s not getting enough, and it starts looking misshapen and sad.
8. It doesn’t flower
This only applies to flowering plants – e.g. hoya, orchids, african violets. If you have a plant that you know flowers readily indoors and it isn’t, try increasing the light.
This year I tried keeping my thanksgiving cactus on my coffee table (excellent light there) to see if it would flower without me having to shift it round my house looking for a dark spot. It did. The natural temperature drop and shorter days did all the work for me.
9.Loss of variegation
This is contested. It could be a factor. P. paraiso verde’s variaegation is apparently heat dependent. My P. pink princesse’s seems 100% random. I do think low light can cause Florida ghosts to be a bit more mintly rather than ghostly.
10. You think it might need more light
If you think your plant needs more light, it probably does. I live in the UK so the light is NEVER going to br bright enough to damage my plants long term (they can burn to a crisp, but that’s only happened when my plants have been outside and they invarisbly come back bigger and stronger).
IN CONCLUSION: those articles that claim certain plants can tolerate low light levels? Lies to sell plants. Also remember that a lot of photos for magazines are staged and have massive budgets. That £500 fiddle leaf fig will NOT survive in a dark corner
