Roots take in water, leaves take in sunlight. Everyone knows that. But plants also need air, and that’s less well understood. What about orchid roots—do they need air, and what would they do with it? What happens if they don’t get any?
Do orchid roots need air? They do. Orchids absorb air through both their roots and their leaves, through tiny holes called stomata. They need the carbon dioxide in air to perform photosynthesis and make sugar/food. Orchids typically have some roots that sit outside the pots, referred to as ‘aerial roots’ or air roots, for this purpose. You can safely bathe an orchid in 15 minutes to water it without it ‘drowning’, however.
The guide below first looks at what aerial roots are, the difference (if any) between normal roots and aerial roots, what they look like and so on. It will then describe what they do, and if you need to trim them.
Do Orchid Roots Need Air?
Orchids need air to grow. They use the carbon dioxide in the air to a) photosynthesize, and b) grow new plant tissue. Even the roots under the surface of the potting mix need air, which is why it’s best to pot orchids in very loose mixes like coconut bark.
Some of this air is absorbed through the leaves. But some is absorbed through the roots, too. If you’re already familiar with this idea, you may have heard the term ‘aerial root’ or air root. But what is an aerial root, and what does one do?
What Are Orchid Aerial Roots?
Orchid aerial roots, or air roots, are roots that sit above the surface of the potting mix. Rather than poke down into the mix, they grow off into the air like long tendrils. They look almost like they’re reaching for something!
What Are Orchid Air Roots (vs. Normal Roots)
Biologically speaking, there isn’t any difference between air roots and normal roots. They look the same, they can perform the same jobs, they grow from the same parts of the orchid, they’re made from the same things (and so on). Rather, it’s because of how we grow orchids in our homes that we’ve come to make this distinction.
An aerial root is a root that pokes out of the pot, or up into the air. A regular root is one that sits inside the pot itself and, if you use any, is wrapped in and around the potting mix.
What Do Orchid Aerial Roots Look Like?
Aerial roots look exactly the same as regular roots. They’re biologically the exact same, with the same internal structures, and made from the same things.
But that doesn’t mean you can’t tell which root is an aerial root and which root is a normal root. That’s because the difference between aerial roots and normal roots is that the aerial roots are above the level of the potting mix. So, the aerial roots are the ones poking out of the pot, and the normal roots are the ones inside the pot.
As for every other aspect of their appearance, they’re the same. They’re silvery gray along their length, and can range in thickness from a pipe cleaner to a thick power cable. If they’re actively growing, they have red-green tips with a pointed end. They look wibbly-wobbly, like floating tendrils, but they should feel firm and bounce back to their position if you bend them. They can become wrinkly if they’re a little too dry, but even if your orchid is well-watered, there will be slight grooves evident in their surface like the wrinkles on our skin.
Orchid Aerial Root or Flower Spike?
Aerial roots and flower spikes are easy to tell apart.
To start with, they’re different colors. As stated above, aerial roots are a silvery-gray color. They also have green-red tips if they’re actively growing. They may have points where they get narrow before suddenly flaring out again (a sign that they stopped growing, but started again later). They are wavy like tendrils, and grow in seemingly random directions.
Flower spikes, on the other hand, are the same kind of green as the stem and leaves they come from. They start out as a light green, before deepening to a deeper green, a shade or two darker than the plant. At no point are they gray or silver. When they die, they turn brown and shrivel up.
Besides that, aerial roots and flower spikes grow from different places. New aerial roots grow from the stem of the orchid—the part that’s still green, anyway. There may be some in the dried-up brown stem below, too, if your orchid is old enough. Flower spikes, by contrast, grow from the gaps between leaves. Let’s say your orchid has six leaves: well, the flower spike will grow from the gap between one of these leaves and the leaf above it. It will emerge from the center of that gap.
What Do Orchid Aerial Roots Do?
Orchid aerial roots perform two jobs. They can absorb water, and they can absorb air. The roots that are below the surface of the pot are the ones that do the ‘heavy lifting’ with regard to absorbing water, of course; so that means the aerial roots are the ones that absorb most of the air.
This gives them an important job, as orchids need to respire. They need to absorb carbon dioxide from the air both to perform photosynthesis, and to create new plant tissue.
If you water your orchid by bathing it, then this job becomes even more important. An orchid won’t instantly wilt and choke if all of its roots are under water, but it’s best if some are left in the air. The aerial roots can absorb air while the roots below absorb their water.
How Do Aerial Roots Breathe?
Roots breathe in the same way that plant leaves breathe.
Well, ‘breathing’ is maybe a misleading way of putting it. Obviously plants don’t have lungs like animals do, so they don’t breathe in and breathe out exactly like we do. But they do still take in air, use some parts of it, and get rid of any air they don’t use.
They do this with tiny holes called stomata. These are found both in the leaves, particularly on the undersides of the leaves, and in the roots. They open when the plant wants to take more air in or push more air out. The carbon dioxide in the air is used during photosynthesis to create sugar, which the plant uses to sustain itself.
What Do You Do With Aerial Roots on an Orchid?
You don’t need to do anything to an orchid’s aerial roots. You can leave them to grow naturally, which is what would be best for your orchid.
While orchids aren’t as clever as we are—otherwise we’d be the ones kept in pots—they do know one thing, and that’s how to grow. It knows when it should grow a new leaf or leaves, or when it should grow new roots, or when it should grow a new flower spike. It conserves its energy and uses it for what it knows is best.
Can Orchid Aerial Roots Be Trimmed?
Orchid aerial roots can be trimmed. You trim them like you would trim anything else on an orchid. To do so, you should:
- Identify the points you want to cut in advance. You don’t want to cut away every aerial root, as they perform an important role.
- Trim using a sharp tool. The sharper the tool, the cleaner the cut, which will help your orchid heal.
- Trim using a sterile tool. If you don’t use a sterile tool, you may introduce bacteria into the cut you make. You can buy single-use razor blades, which are sterile tools, or hold a tool over a flame to sterilize it.
- Seal the cut that you make, e.g. with cinnamon. Sealing the ‘wound’, especially with something antibacterial, will prevent infection.
The question, though, is why you would need to do this!
Do You Need to Trim Orchid Aerial Roots? (Orchid Aerial Roots Too Long)
There’s typically no need to trim an orchid’s aerial roots. They aren’t a sign of ill health; far from it. They’re a sign that your orchid is in great health. You want your orchid to grow lots and lots of roots, as they make it more effective at picking up water and nutrients. This in turn leads to bigger leaves, bigger blooms, and less chance of succumbing to ill health (like infection). If these aren’t things you want, why do you even grow orchids!?
There will, occasionally, be a reason you need to trim an orchid’s aerial roots. If one of your orchid’s roots becomes damaged or rotten somehow, you should trim it away. Rot is highly unlikely to occur on an aerial root since standing water is what makes rot happen, but if it somehow did, you’d want to trim it away. You could also trim them for aesthetic reasons, i.e. if you think the orchid looks better without them. But orchids do best when they’re allowed to grow as they like!
You can also remove aerial roots that are long since dead. These are dried and shrivelled and don’t serve any purpose.
Do You Need to Mist Orchid Aerial Roots?
Misting your orchid’s aerial roots is a good way to give your plant a little water between waterings. While misting elsewhere can cause problems like crown rot, spraying your orchid’s aerial roots is fine. Give them a light misting.
You shouldn’t leave your orchid damp or wet at all times. If you do, it will encourage fungal and bacterial infection. As such, you should wait for the outside of the aerial roots to be dry before you consider spraying them. You can also consider not misting them at all, which is what we do, and keep the humidity high in other ways. You could use a humidity tray or a humidifier (the opposite of a dehumidifier) instead.
What to Do If Orchid Aerial Roots Dying
If you notice your orchid aerial roots drying out, the first thing you should do is figure out why. The probable reason is that your orchid isn’t getting enough water. The same thing happens to regular roots: they shrivel up and die if they don’t get enough water. You may also notice a slight brown-black discoloration at the end of the root.
I would recommend leaving the root in place until it’s fully dried. You can then cut it off anywhere along its length, although since it won’t grow back, it makes sense to cut the whole thing off. The reason I think waiting is best is that when a part of an orchid dies, the orchid tries to seal it off. This makes it dry out quicker; but it also means that any cut you make to the dead part then can’t get infected, because it’s dead tissue. If you cut a root that’s still partially alive, an infection could develop. There’s also no harm in leaving the roots there, even permanently, so there’s no rush to get rid of them.
You should also start watering your plant more if its aerial roots are shrivelled and dead. A fully dead root can’t recover, but one that’s partially dried out can. It will absorb lots of water and become somewhat plump again, although it will never look like it did before. But it’s at least still functional, so is useful for the orchid to have.
All that being said, lack of water isn’t the only reason orchid roots can become shrivelled. I have an orchid that experienced a fungal infection, and one of the symptoms was that its new roots emerged with black tips rather than green (which is a weird sight to see). These roots failed to thrive, and not because I wasn’t watering the orchid enough—I watered it the same amount as I watered all the others. My guess is that the orchid was under a lot of stress, and so gave up on its new roots, not sending them enough water. They’re still there—I haven’t cut them away—and they’re black and shrivelled despite getting enough water. So you should rule out an infection or other stressors to your orchid, too.
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