Aerial roots are one of those things that I had NO idea about until I started collecting houseplants.
They can be so creepy! And grow SO fast!
I’m going to try to cover the basics of houseplant aerial roots in this article. A lot of different plants grow them for various reasons, so I’ll link additional articles that go into detail about the attributes of different aerial roots on different plants.
Consider this an aerial root whistle-stop tour.
What is an aerial root?
An aerial root is a root that…grows in the air.
It’s a type of adventitious root, which is any root that doesn’t grow from the radicle.
The radicle is the root system that forms from the germinating seed, though I suppose in houseplants it’s the root system that forms from tissue culture or a propagated node.
All aerial roots are adventitious, but not all adventitious roots are aerial roots. Kind of. The line is a bit blurry around things like moth orchids because they're epiphytes and all their roots are aerial roots.
What’s the function of aerial roots?
Different plants use their aerial roots, but there are three main reasons a plant may produce aerial roots:
Aerial roots can be used to climb
Climbing is the primary reason plants produce aerial roots. It allows them to attach to trees or rocks and grow taller without risking falling over and snapping.
A lot of aroids have a juvenile form and a mature form, so their leaves change as they mature.
Common houseplants with very different juvenile and mature forms are Monstera deliciosa, Syngonium podophyllum, Epipremnum aureum (Golden Pothos), and Monstera dubia.
The switch in their genes that tells them to change leaf shape is activated by an increase in the amount of light they’re getting and the height that they’ve climbed to.
When aerial roots are growing they’re white and fuzzy, so they can stick to tree bark or rock (but not glass – my heartleaf Philodendron tried though).
As they age, they gradually turn brown, and weld to whatever they’re climbing so strongly that you can’t easily remove them without damaging them.
Aerial roots can help with stability
Stability is important for climbing plants, so they often produce more aerial roots the higher they climb. There can be a lot of tropical storms in the native habitats of climbing plants, so they need to be secure.
However, true epiphytes, like Phalaenopsis orchids don’t have any roots in the ground – they rely entirely on their aerial roots for stability. They spread their roots as far as they can, attaching to whatever they can find, to reduce the risk of being knocked down.
That’s why orchid aerial roots grow in every direction – they want to be as secure as possible.
Aerial roots can absorb water and nutrients
The extent to which plants can absorb water and nutrients through their aerial roots depends on a couple of things:
1 – The type of plant
Epiphytic orchids don’t have any roots in the ground, so their aerial roots are very good at absorbing nutrients and water – because it’s the only way for them to get them. Sustenance is the primary function of the roots.
Stability is great, but if the orchid is knocked out of a tree, it can survive on the ground. If it can’t absorb water, it’s toast.
Most aroids, on the other, hand don’t really need their aerial roots to absorb water and nutrients – they have subterranean roots to do that for them.
That being said, there are situations when aerial roots can be called upon to take more of an active role in keeping their host alive.
2 – Whether the roots are needed to absorb nutrients and water
A lot of climbing aroids are hemi-epiphytes, which means they start off life in the ground and climb trees. In most cases, the aerial roots are used to climb, and the subterranean roots are used for water and food.
However, if something happens to the stem of the plant and the roots can no longer provide nutrients to it – for example, it’s severed or crushed – the aerial roots will become the breadwinner.
How far they're willing to go with this depends on the plant. Most climbing aroids live in very humid environments, so they can get enough moisture from the air and the bark of the tree they're climbing.
However, some aerial roots, for example, those on Monstera deliciosa, are attracted to water, so the aerial roots can grow down to the ground and become subterranean roots.
It's probably this habit of producing really long aerial roots and significantly increasing the size of their root ball over time that led to the success of Monstera deliciosa, not just as a houseplant but as a literal invasive species. Impressive stuff!
Are there different types of aerial roots?
So, the internet claims that there are four different types of aerial roots:
- Strangler roots
- Pneumataphores
- Haustorial roots
- Propagative roots
However, I propose that there are seven types of aerial roots:
- Climbing roots
- Epiphytic roots
- Panic roots
- Strangler roots
- Pneumatophores
- Haustorial roots
- Propagative roots
We’re unlikely to come across pneumatophores or haustorial roots in the houseplant world.
Pneumataphores are really only found in specific mangrove species. The plant basically uses aerial roots as snorkels so the roots can get oxygen in waterlogged soil.
Haustorial roots are parasitic roots (e.g. bird’s nest orchids) that invade another plant’s roots to steal its nutrients. I can’t think of any houseplants with haustorial roots – even ivy roots aren’t parasitic, they’re just destructive.
Ficus have strangler roots – they begin life as epiphytes living in trees and send aerial roots down to the ground, giving the effect that the host tree has been strangled (ironically, the trunk’s fine, the issue is that the Ficus is now taking all the nutrients and moisture from the soil).
I have a couple of huge Ficus, and I’ve never had an issue with them throwing their aerial roots around, so again, this isn’t an aerial root type we have to worry about.
There is an aerial root growing on my little Ficus shivereana, but I’m not sure if it’s just a normal root that’s got lost.
A few houseplants have propagative roots, so they send out runners which then root in the ground – ferns, some Monstera, and spider plants. Sometimes they just grow that way, like crawling Philodendrons, rooting themselves as they go.
Houseplant aerial roots, such as those used for climbing, or that are found on epiphytes like orchids, don’t fit into any of the four aerial root types.
I suspect this is probably due to a general lack of research into aroids.
Instead, botanists just call them adventitious aerial roots and go and research mangroves. AND there’s no special term for the aerial roots that succulents grow when they’re panicking about lack of moisture.
Which houseplants have aerial roots?
Loads of houseplants produce aerial roots.
Some produce them routinely and we all know about them, like Monstera deliciosa, some don’t really need them in captivity so they don’t often bother growing them, like rubber plants.
Climbing aroids
Climbing Philodendrons, Rhapidophora, Monstera, Epipremnum, Syngonium, Scindapsus, climbing anthuriums, Amydrium…I’ve probably missed some.
Anyway, all of these aroids have aerial roots, but the rate at which these roots grow when kept as houseplants varies a LOT. Some just don’t like growing aerial roots (not mentioning any names, but also…P. verrucosum), some need high humidity, and some just want something to climb.
Some won’t grow an aerial root for years, then a metre-long one will grow seemingly overnight, and for no apparent reason.
(Monstera deliciosa, I’m talking about you.)
Hoya
Not Hoya are epiphytes, but a lot of the ones in the houseplant trade are.
They also don’t all grow aerial roots, but many do. Don’t worry if your Hoya doesn’t have aerial roots – they’re definitely surplus to requirement when they’re kept as houseplants.
Hoya are epiphytes and primarily use their aerial roots to secure themselves to whatever they’ve climbed.
They climb by sending out vines, whipping their vines around until they hit something they can climb, and then wrap around it.
Then leaves will grow. Aerial roots will form when the Hoya hits something solid (like a tree branch). Or also sometimes just because they want to.
Rubber plants
Rubber plants are known for their aerial roots in their natural habitat.
They were used for making ropes, and an important part of the local economy. However, they’re less likely to grow them when they’re kept as houseplants, BUT the roots are quite happy to grow out of the soil.
Orchid
Epiphytic orchids are ALL aerial roots – that’s why we tend to keep them in orchid bark, not soil.
Their roots are designed to be out in the open air because they can photosynthesise. If you struggle keeping orchids alive I highly recommend you try keeping them in no substrate and just soaking the roots weekly.
Succulents
Succulent aerial roots aren’t quite the same as the other types of roots, in that they’re not meant to be there – they grow as a response to adverse conditions. That’s why I proposed the name ‘panic roots’.
They’re usually pink or white and grow on the stem of your succulent. They’re a way of your plant getting more water, so it’s a sign that you’re not watering often enough. They can also crop up when your succulent deems its environment to be too humid.
Succulent aerial roots aren’t harmful, but they are a sign that your succulent isn’t getting what it needs.
Ivy
Ivy aerial roots need their own section because they’re so voracious.
I don’t recommend keeping ivy as an indoor plant, because they’re basically spider mite factories. If botanists discover that ivy produces spider mites I wouldn’t be at all surprised.
My views aside, if you have an indoor ivy, try to keep it away from your walls.
Their aerial roots are sticky and great at clinging to things, and they can cause damage, both by exploiting cracks in walls and causing structural damage or by sticking to your wall and ruining paint or wallpaper.
Ferns
Ferns produce propagative roots. They’re not looking for something to climb, they’re putting out a runner and if you lay the aerial root (it’s actually a stolon, or horizontal stem, but I appreciate that it looks like a root) on the ground, it’ll root and produce a pup.
Do houseplants need aerial roots?
Epiphytes like orchids obviously do. All their roots are aerial roots.
But if we’re talking about aerials in addition to subterranean (or, you know, normal) roots, then no.
Especially climbing plants like Philodendron and Monstera. We make sure they’re hydrated and fed, and even if they snap and need a new root system, they don’t need their aerial roots for that, because we can propagate them from their node.
An aerial root is helpful, but not necessary.
However, I like to encourage my plants to grow aerial roots, because if I have them growing vertically, rather than leaning all over the place, I can fit more plants in my house.
Do aerial roots grow new plants?
No, you can’t grow new plants from aerial roots.
If we’re talking propagative roots, then once the new plantlets have reached a certain size you can sever them from the mother plant and grow them on.
But if we’re talking climbing aerial roots, like those on a Monstera or Philodendron, they can’t grow new plants. If you cut them off, they’ll just die. It’s the equivalent of cutting off someone’s arm.
Cuttings with aerial roots do root more quickly, because an aerial root can switch to an underground root.
Research into this is in the early stages, but it's thought that when aerial roots hit the ground, the plant reduces the amount of raphides (these are the calcium oxalate crystals that plants use to make themselves toxic and therefore less attractive to herbivores) in the roots. This signals to the plant that the aerial root is now an underground root and it starts splitting and diving into a whole new root system.
Advantages of aerial roots
- A plant with healthy aerial roots is easier to train to grow nicely
- A healthy aerial root system can encourage the plant to grow bigger, more mature leaves
- Aerial roots provide stability, so your plant is less likely to fall over and snap
- Rooting cuttings with an aerial root is quicker
- If something does happen to your plant’s root system, like root rot, a plant with a healthy aerial root system may take less damage – so you might not get so many sad-looking leaves
Disadvantages of aerial roots
- They can look messy if they’re not tamed
- Sometimes plants devote more time and energy to growing aerial roots when you’d really prefer a few more leaves
What causes aerial roots to grow?
In the wild, aerial roots just grow. I used to assume that they started to form when the plant reached a certain age or size, which might be true in their natural habitat, but I have a baby Monstera with an aerial root that it does NOT need.
Houseplants also grow aerial roots as and when they feel they need them, but there are things you can do to stimulate their growth.
Different things work for different plants, and there is also variation between different plants of the same species. However, if you have a plant that you think should have aerial roots, and it doesn’t, it could be one of several issues.
I’m going to assume that the plant is growing and otherwise healthy. If it isn’t, you need to sort out that first.
Light
Plants produce aerial roots so that they can climb towards the light. If the plants is healthy and already propped up on a pole or stake of some sort, increasing the light it gets can kick-start aerial root growth.
Humidity
Humidity can convince even the most reticent aerial root-growers to start producing them. Be warned though – aerial roots that have been grown as a direct response to very high humidity are extremely creepy-looking.
I got a heartleaf fern to grow these freaks by keeping it in a terrarium, but a grow cabinet or something similar (like a clear plastic box) will work well.
You’d probably struggle to get these results using just a humidifier unless you’re willing to live in 85% humidity (which I don’t recommend).
You’ll also need to keep the environment warm (above 18˚C/65˚F) otherwise you risk rot.
Genetics
A lot of Philodendron cultivars don’t like to climb. They’ll grow aerial roots, but they won’t attach, or they’ll randomly let go of the moss pole, or they won’t grow them at all.
This is usually a case of when the cultivar is a hybrid and there’s a crawling and/or self-heading parent/grandparent.
Philodendron Pink Princess is an example of a climber who isn’t actually that good at climbing.
There are also just…differences. I have a Philodendron brasil that I keep as a trailing plant and it LOVES producing aerial roots. I have another plant made from cuttings of the same plant and it doesn’t really grow them.
It wants something to climb
Some plants won’t produce aerial roots until they have something to climb – this is usually the case with vining plants like Monstera adansonii and Golden pothos. They just get little brown nubs when left to trail.
Not all climbing apparatus are made the same.
- Cheap coir poles, bamboo canes, trellis
Great if you just want something to keep the plant neat, but the aerial roots won’t really grow unless the humidity is super high. Sometimes they will grow if you have awesome conditions, but its unlikely without humidifiers and grow lights and a perfect care regime.
- Moss poles
Moss poles filled with real moss are great for encouraging aerial roots, but those aerial roots will grow into a subterranean root system. You’re basically layering the plant as you grow it. It does make propagating super easy and the plants grow much bigger much faster BUT you do need to make sure to keep your moss fed and watered.
- Kratiste poles, wooden stakes
Kratiste poles seem to work in ambient humidity, and wooden stakes/planks should but you might need to tape the stem to the wood to make the plant realise that it’s there and start producing aerial roots.
The aerial roots will work as aerial roots, so they’ll keep the plant in place and help it climb. They will encourage bigger leaves but not to the extent that a moss pole would. They don’t need any maintenance though.
What to do with aerial roots
In the case of things like Hoya, they don’t usually grow big enough to be an issue – they don’t have extroverted aerial roots, it’s the vines you have to watch out for.
In fact, out of all my plants the only one that I need to keep an eye on the aerial roots on is my Monstera deliciosa.
I suspect that if you’re trying to find out what to do with aerial roots, it’s Monstera aerial roots that ail you.
This warrants its own article, so here’s a specific one on what to do with Monstera aerial roots.
Here’s a brief overview of your options:
- Leave them be. They won’t hurt anyone (except possibly the paint on your walls)
- Poke them back into the soil. That’s my move
- Give the Monstera something to climb, and use the aerial roots to attach it
- Put the aerial roots in water – this is largely pointless and a bit of a faff, but it is fun
- Cut them off – it doesn’t really need them, unless you’ve directed them back into the soil and it’s using them for support
In summary
- Most houseplants with aerial roots use them for climbing
- They probably don’t need them in a houseplant situation
- Your rubber plants definitely don’t need their aerial roots
- Your succulent with aerial roots is crying out for water
- Your phalaenopsis definitely needs its aerial roots – they’re the only roots it has
- Keep an eye on your ivy – it will destroy your paintwork, given half a chance
