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I’ve done a few articles on aerial roots, but they tended to focus on aroids, which produce aerial roots to allow them to climb up trees.
And then there’s succulents which grow aerial roots as a last ditch attempt to get a little bit of moisture before they perish.
Orchid aerial roots are more similar to aroid aerial roots, but they don’t use them to climb – they do use them to anchor onto a tree for stability though.
I’m going to mainly talk about Phalaenopsis orchids here, though I will touch on other orchids where it’s relevant.
Phalaenopsis are the most common house plant orchid – they’re the one’s that people buy in the supermarket for a tenner and just replace when the blooms are done (sob).
What are orchid aerial roots?
In the case of Phalaenopsis, all of the roots are meant to be aerial roots. They’re true epiphytes, so they don’t grow in the ground at all.
Monstera, on the other hand, are hemiepiphytes, so they begin their life in the soil, and then grow into epiphytes as they develop. Whilst they keep their roots in the ground, their aerial root system will grow grow so extensive that should the stem be severed, the plant can still survive.
Phaelaenopsis don’t grow in the ground in the wild. All of their roots are aerial roots.
Aerial roots are very adaptable. If they’re cultivated to grow in soil, then they can adapt to it very well. However, they’re best grown in substrates that are very airy, hence why we typically grow them in orchid bark.
Orchids are a MASSIVE family of plants. I think the second biggest one next to asteraceae (daisies). There are plenty of species that grow terrestrially (i.e. in the ground like regular plants) so be sure to check the species of orchid that you have.
Miltonia are also epiphytes, as are several others like Dendrobium and Cattleya – they’re all listed here.
Why do orchids produce aerial roots?
We’ve already covered that they grow aerial roots so that they have a secure anchor to the tree that they’re growing on.
They’re not parasitic, by the way. They don’t harm the plant they’re growing on. Just along for the ride.
This heading should be something more along the lines of ‘why do orchids produce aerial roots like that?’ i.e. freaking everywhere. They grow straight up out of the substrate, crawl along the desk, out of the window…wherever the damn like well please.
The answer to that is just…it makes it more likely that they’ll survive. Statistically, the further they spread their aerial roots, and the more aerial roots they grow, the more solid their foundation, and the less chance there’ll be that they’re knocked off their perch.
Whilst orchids can survive if they’re knocked to the forest floor, there’s a much higher chance that they’ll get rot, get trodden on/eaten, or just end up somewhere that doesn’t have enough light for them to grow.
How many aerial roots should my orchid have?
As many as it likes.
There’s a rumour circulating a few of the Facebook house plant groups that if your orchid is puching a lot of aerial roots out of the substrate it means that your orchid doesn’t like whatever you’ve potting medium you’ve used. Or you’re over/under watering it.
This is just a myth. Orchids just throw their roots anywhere with abandon. In fact, an orchid with a plethora of aerial roots is usually a happy fella.
Some orchids produce a lot of aerial roots from each node, especially if you keep it in a high humidity environment. This is just a survival mechanism – if the stem gets snapped, a node with a few aerial roots is a couple of steps closer to being able to successfully root itself than one that doesn’t.
The reason humidity makes orchids grow more aerial roots is…they like higher humidity.
Quantity of aerial roots also depends on the species or variety of orchid that you have.
Some grow more, some grow less, others don’t grow them at all.
As I mentioned, many species, such as Paphiopedilum only grow in the soil, and will not appreciate having roots outside of the potting medium. They’ll most likely just shrivel up and dry out, er, permanently.
As for rations of aerial roots to roots in the pot, the general rule of thumb is that at least half of the roots should be in the pot.
Obviously, NONE of them need to be in the pot. They’re epiphytes and can live in the open air.
It’s just a major ballache to get them adequately hydrated that way. It’s fine when they’re using their aerial roots to drag water out of a living tree, but that’s hardly a setup one can replicate in one’s living room.
I just soak it when the roots are all silver. Is it a ballache? Yes. But it’s also the easiest way to make sure it’s getting enough water (but not too much).
Should you mist orchid aerial roots?
One of the pretty unique things about Phalaenopsis and other epiphytic orchids is that their roots can photosynthesise. When they’re wet, they go green, which is the chlorophyll at work.
This is another reason we keep orchids in airy substrate and clear pots – it allows light into the roots so they can photosynthesise.
However, for the roots to photosynthesise, they need to be kept healthy, and this means adequate moisture.
In general, hardier orchids like Phalaenopsis are perfectly content to grow *working* aerial roots in humidity levels of 40% plus without the need for misting. If your air is drier, then misting is a great way of dampening them (not for increasing humidity though) but you can also just sit them in water for half an hour.
Don’t leave them in water for long periods of time – it can lead to bacterial growth. You can develop them by leaving them in water, but you need to make sure you’re oxygenating the water properly.
Can I cut off orchid aerial roots?
If you don’t like the look of them, you can chop them off, but experts advise against it (I got a lot of info from MissOrchidGirl, she’s the GOAT). Orchid aerial roots are quite wide in diameter, and you can easily introduce infections and bacteria into the wound.
Also, if you’re pretty new/lack confidence in caring for orchids, cutting off roots is generally inadvisable because if the roots in the substrate deteriorate for whatever reason, you’ve hacked off your backup.
What colour should my orchid aerial roots be?
The colour of orchid roots depends on the species. Phalaenopsis roots are silvery, Dendrobium roots tend to be creamier:
Fun fact: the outer casing of orchids roots is called the velamen, and it’s a spongy layer designed to protect the roots from UV damage (we think) and excessive water loss.
Some orchids also have a symbiotic relationship with fungi – they allow them to live in the velamen, and the fungi help them absorb nutrients from the air, allowing them to live in places other plants can’t.
After the roots are adequately hydrated, they go green, because they’re photosynthesising.
Can I plant orchid aerial roots?
If you have very dry air, you may want to plant your orchid’s aerial roots, rather than watching them slowly shrivel and disintegrate into dust.
You totally can; it’s the same process of planting Monstera roots but with a higher chance of failure.
Whilst Phalaenopsis roots are pretty hardy, they’re not designed to live in soil. Make sure the rest of the subterranean roots are happy before resigning the aerial roots to the same fate.
Also, be gentle. If the aerial roots are growing straight up out of the soil, you may need to soak them first to make them a little more pliable and less likely to snap.
Monstera aerial roots are adventitious – they grow from somewhere unexpected and are separate from ground roots BUT they can adapt into ground roots if planted.
Orchid roots are ALL aerial roots (in epiphytic orchids anyway) that would pretty to live in the open air. However, they can be grown in such a way that some of their aerial roots are adapted to live in a substrate such as bark, moss, water, or leca.