What is an Orchid Plug?

There are probably two ways that you’ve heard the term “orchid plug” and are now wondering what that is. When searching for new orchids to grow, you will eventually come across orchids that are sold in plugs. The other way is if you were reading about repotting orchids and was told to remove the orchid plug from the center of the pot. Either way, the plug that both are referring to, is the same thing.

An orchid plug is a wrapping made of peat moss or coconut fiber mixed with sphagnum moss that is wrapped around the roots of young seedling orchid plants. The plug is specially made to protect the very thing, young roots as well as provide frequent airflow and retain moisture.

I’ve commonly heard that these plugs are called the plug of death, but that’s a bit unfair in my opinion. There is nothing deadly about the plug. If it was so deadly, then orchid growers wouldn’t use it. Yet to be fair, it must go… and in this article, you’ll learn why.

Healthy Orchid Roots
Image Credit: © 2021 Orchideria.  All Rights Reserved.


The Purpose of the Orchid plug

Since the very new phalaenopsis roots are so young and tender, they don’t respond well to climatical changes, watering gaps, inconsistent humidity, or even fertilizer overloads.

In real life, these tiny orchids would still be attached to the mother plant, having been formed either by a keiki (at the end of the Phalaenopsis flower spike) or by the seed that attached to bark and found a fungus that could take care of it. If you want to know more about keikis, this article I wrote may help.

In the pot, neither of these occur. There is no mother plant to regulate the intake of water, nor is there a fungus that provides all the nutrients this orchid seed needs to mature. The small young plant is out there on its own and fighting to learn as quickly as possible how to retain water, how much water to retain, how to distribute this around the leaves and even though it’s a plant, it still has a learning curve to adapt in this world.

Once the orchid has sufficient roots and leaves to leave the flask with agar that it had been growing in previously, the orchid is now transferred into its own little pot…Well, close enough. It is going to be sitting on a plug tray, a plastic, egg-crate-looking tray that separates each orchid from the others.

An orchid plug is placed around these tender new roots so they can be protected from the outside tray. The material allows the roots to penetrate it easily, without injuring the new orchid root tips.

The plug is specifically designed not only to absorb humongous amounts of water but also to retain that water for long periods of time. This makes orchid growing cost-effective for the growers. The roots can safely grow in this media for two to three years before the roots start to grow out of the plug and poke through the little plastic cup.

Are Orchid Plugs Bad?

If orchid plugs are this good for the Phalaenopsis orchids, then why do so many orchid growers say to remove it when repotting? So many, including me…

Think a little about the potting media that your orchid will now be going into. It probably will be a mixture of sphagnum moss and orchid bark. Maybe a little perlite and charcoal to finish off the mix. This mixture will have a specific drainage speed, it will allow airflow and gas exchange at a specific rate, it will absorb and release fertilizer all differently than the plug will.

While the plug is still quite efficient at absorbing water, the orchid bark is not.

So, the middle of your pot (which already has a high propensity of evaporating more slowly) will be extremely moist, the exterior of the orchid pot with the bark will dry out very fast. The roots that will grow outside the plug will have two specific conditions to grow in and will not adapt well to that.

The problem isn’t the plug. The problem is that the plug with another type of potting media will make the roots retain too much water. I evaluate my orchid’s watering conditions by feeling the top of the pot. If it’s dry, then I need to water.

At best, I place my finger 1 inch into the potting media and see if it’s moist there. If not, then I water. If you want to know more about watering orchids, then this article I wrote may help.

If I use the finger test and the orchid has been potted with the original plug and new potting media around it, my finger will never reach the middle of the pot. I don’t know how much water is in the plug. Probably a lot, still not evaporating as quickly as the outer rim of the potting media.

I feel that it is dry, so I water again… and again… and again.

With this constant watering, the middle roots inside the plug die off. The velamen (a root covering that protects the roots and multiplies the surface area of the root so more water can be absorbed) allows water to enter, but not exit. It’s a one-way ticket to drowning.

Many growers then blame the plug, which, unfortunately, was not to blame. It’s the different potting media mixed together that is to blame. You can keep the plug on the orchid if it hasn’t been in the pot for more than three years (hard to know exactly) or if the roots haven’t out grown the pot.

How do you grow orchid plugs?

Orchid plugs have their advantages. If you buy a flask (usually the cheapest option available with lots and lots of orchids to choose from) and want to grow them into fully mature adult plants, then you will need to transfer the orchid seedlings into plugs at some point.

Usually, the roots have had time to develop, and the leaves are healthy enough o photosynthesize on their own. The seedling is at a point where it can live independent of the agar that is in the flask, which provides nutrition.

If you have read about keikis, the same principle applies to seedlings. They still will be small tender plants that need extra humidity and watering. Some plugs are specially made that you can buy to accommodate these seedlings.

This will provide extra care and protection since the seedlings will grow at the same pace and you can water uniformly. Each plug will not be connected to the next orchid plug, which avoids fungi from spreading inside the orchid tray.

Removing Orchid Plugs

When it’s time to repot, you need to remove the old plug from the center of the pot. What happens in nurseries and garden centers is that to keep costs down and water evenly, the orchids are not removed from the plugs when they outgrow them. They are what’s called up-potted. I wrote an article about up-potting orchids, and you can read it here.

So, the nurseries up-pots the orchid the first time, adding new media around the old plug. It’s fast and effective. They are going to sell the orchid anyway, so why go to all the work to remove the plug? It also keeps the roots safe, so the orchid doesn’t feel it.

Then the next flowering season passes, and the orchid, unfortunately, doesn’t sell. The roots grow, expand, and now it needs to be repotted. So, what does the nursery do: they up-pot again.

By the time this orchid gets to you, the original plug has long gone sour. The pH of the middle of the plug is horrendously low, full of rotting roots and a bacterium farm. So, when you repot your orchid, you need to remove the orchid plug from the center and clean up all those dead roots.

If they are yellow but firm, don’t remove them. I wrote an article about how to remove roots and yellow roots, which you can read here.

Can I use Rock Wool Plugs for Orchids?

Rockwool is an option that many orchid growers come across. It is commonly used for boosting seedling growth in other plants, mainly hydroponic plants or in hydroponic systems.

Rockwool is purely inorganic and does not decompose over time, as sphagnum moss will. When most people think of rock wool, they relate it to insulation. The material is almost the same, but not quite.

So, when you are looking for rock wool, be sure to get the horticultural rock wool, not the home insulation stuff. Horticultural rock wool is basalt that has been melted down and made into fibers. It simulates a glass texture, so be careful to wear gloves.

The rock wool that is used in home insulation is the same material but made differently. That will decompose and become mushy—you want to always avoid that.

Rock wool will decrease in size, but this takes years. I have not used rock wool myself, is what I’m going to say now is purely my observations and notes from what I’ve read.

For the cons:
most people say that the rock wool doesn’t allow much airflow, and the orchid roots tend to rot because of this.

For the pros: the absorption of water is excellent and stimulates the root growth.

If you decide to go with rock wool instead of peat moss and coco fibers, then you’ll need to soak it first. And I mean really soak it. Days (plural).

When rock wool comes straight from the bag, it will have a higher pH level, almost near 8. With constant leaching, you can bring this pH down to 5.8, where it will remain stable. This happens because the lime has built up in the rock wool and water easily takes that away.

With the advance of technology, some companies are pretreating their rock wool. This means you can open it, soak it to provide a good root stimulant (water), and plug the roots right away. No need to bring the pH down since the factory already did that. So, no matter what brand you use, always get more information on pretreatment.

There are some precautions with rock wool since it is a glass fiber. Use gloves when handling this and if possible, wear a mask. Little glass flakes in the lungs are not a good idea.

I know it’s not pertinent to this article, but since I’m talking about rock wool, some orchids love it as a potting media itself, not only as a plug. These are the more water retentive orchids, like Phragmepediums. They go very well with LECA and rock wool cubes cut up into tiny squares.

From what I’ve read, most growers are either in the 50/50 for LECA/Rockwool or in the 75/25. These were the 2 mixes that had better results. But this is another article altogether, so I’ll just focus on the plugs for now.

Do orchid plugs need to be in plastic?

If you are going to try the seedlings and unflask them, you will need to place them in a tray or in induvial pots after they have been “plugged”. There are trays that you can buy, like the plant trays for seedlings. Just make sure these have sufficient drainage since plugs will absorb more water than normal soil (or any other media for that matter).

You don’t have to use the trays, but it’s easier to water and maintain humidity if the orchid seedlings are close together.

In all, that’s about it for orchid plugs.

Don’t Stop Learning!

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Signature Amanda Matthews


Amanda Matthews

Amanda Matthews is a theological professor, author, pastor, and a motivational speaker. She's passionate about spreading hope and teaching. Her hobbies include biking, cultivating orchids, and exploring nature trails. She now lives in Kansas, while raising her two children. To read more, go to https://orchideria.com/about-the-author

One thought on “What is an Orchid Plug?

  1. “An orchid plug is a wrapping made of peat moss or coconut fiber mixed with sphagnum moss that is wrapped around the roots of young seedling orchid plants.”
    Possibly, but most commercial nurseries use horticultural foam plugs. Plants are typically not potted into the foam, but against the pot with the foam insulating the roots on one side and the pot on the other.
    “If you buy a flask (usually the cheapest option available with lots and lots of orchids to choose from) and want to grow them into fully mature adult plants, then you will need to transfer the orchid seedlings into plugs at some point.”
    Untrue. A home grower has no need to use plugs when deflasking. They are used by commercial nurseries because they hold a specific amount of water for a specific amount of time, allowing them to water thousands of plants on a specific schedule. In the home, sufficiently large plants can go directly from flask to a mount, if desired. Or they can be potted into sphagnum, small bark, medium bark or a mix of materials, depending on climate and desired watering frequency. The size of the plants out of flask will also be a determining factor as larger seedlings can be potted individually while smaller plants benefit from being placed in a compot.

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