Styrofoam Peanuts and Orchids:
Viable Potting Medium or Not?

Have you ever heard of using Styrofoam peanuts as a potting medium for orchids? Once you have a hand in growing an orchid or two, you might want to try different methods of potting mediums.

Pure sphagnum, if you live in a dry area, bark and perlite, charcoal and sphagnum, semi-hydroponics, leca pebbles, full water culture, Styrofoam peanuts…

Wait, what??
Styrofoam Peanuts in Orchid Potting Medium
Image Credit: "File:Paphiopedilum Rosy Dawn 5zz.jpg" by Photo by David J. Stang is licensed under CC BY-SA 4.0
Packing Styrofoam peanuts has been used for a long time as a potting medium with some orchid enthusiasts giving it positive reviews, yet others sold against it.

In this article, I’ll focus on both sides and at the end let you decide…but I will tell you my opinion first. 
Can you use Styrofoam peanuts for orchids? Yes, but it’s not advisable. The potting medium serves for three purposes: stability, retention of water (and nutrients), and drainage. Styrofoam serves none of these. In essence, Styrofoam Peanuts aren’t recommended as a potting medium for orchids.

Styrofoam Peanuts are Too Light to Stabilize the Roots

Styrofoam was designed to be used as a packing medium to avoid “wear and tear” on your shipping material. They were designed to be lightweight, to not make cost overly high on packing. It is so lightweight, that when Styrofoam is placed in water, it will float to the top.
Styrofoam is actually a name brand used in certain countries; the real name is expanded polystyrene foam. It was registered as a name brand under the company Dow Chemical.

When you chose a potting medium, it needs to be something that will provide stability to the roots and hold the orchid in place. In nature, the roots on the orchid will attach itself to the tree bark, and hold on for dear life. This stability makes the orchid capable of focusing on producing leaves and flower spikes.

If the orchid is not stable, it will not produce any new growth until it feels that it is not threatened by falling off the tree during a rainstorm, strong and violent winds, or a small monkey that runs up the tree to get some fruit. The roots need to hold the orchid in place securely.

When trying to recreate this stability in the orchid medium, the roots will attach themselves to the sides of the pots, and the tiny hairs on the velamen (a fine coating that covers the roots) will cling to the container. They also grab hold of bark, charcoal, perlite, and whatever else is in the potting medium.

That is why it is so hard to repot depending on the orchid. The roots hold on to the potting medium and to remove everything, you’d have to rip away a little part of the root.

Now take all that knowledge and try to associate it with Styrofoam peanuts. It just doesn’t work. The Styrofoam doesn’t provide good stability, because they move around freely in the pot. The surface is something that the velamen can hold onto since it‘s smooth.

Also, when watered, the Styrofoam peanuts float to the top, moving the roots around in the pot.

If you have a massive orchid, it’s more than likely to be a heavy one too. The Styrofoam will not provide the stability to stand upright, making your orchid topple over. The while vase will fall over, and the orchid will plop out on the floor.

In essence, as a way to provide stability for your orchid, Styrofoam fails tremendously.

Styrofoam Peanuts Do Not Provide Proper Drainage

You might be thinking that they do; but nope. Styrofoam peanuts are usually S-shaped or 8-shaped. This form allows water to flow freely through the medium, and exit the pot quickly.

Yet, if a Styrofoam peanut is placed sideways, that water builds up in the curvature of the foam and cannot exit.

This becomes stagnant water and is an open bar for bacteria.

So even if water does freely exit the medium, it can retain water in the same proportion. In other types of medium, the bark or sphagnum would absorb the water. Even charcoal absorbs water to some degree.

But not the Styrofoam.

Styrofoam Peanuts do Not Retain Nutrients for Orchids

The last variant that the potting medium needs to provide is retention of water and minerals—not retention like mentioned above, but retention with a slow release method.

Think of sphagnum moss for example. Sphagnum will retain water, then slowly release it when the conditions are right. This way the roots are constantly moist, but not soggy.

Styrofoam will hold water—stagnant water. It does not release anything.
Image Credit "Cymbidium Hybrid Orchid - Paloma gardens"
by brewbooks is licensed under CC BY-SA 2.0
This is not as important when watering, but what about fertilizing?

To fertilize, (most methods at least) you add the fertilizer to the water. In Styrofoam peanuts as a potting medium, the water will drain through faster than you can blink…and so will your fertilizer.

If you want more information about fertilizer, check out this article about orchid fertilization. It explains 5 unique ways to fertilize since there isn't just one way.

Other reasons that Styrofoam isn’t indicated for Orchids

As for a potting medium, Styrofoam fails in all three tests. But there are other reasons that Styrofoam isn’t the best for orchids.

Some orchid roots are quite hefty and strong, and they’ll penetrate the Styrofoam peanuts rather than go around them. When you repot, they are almost impossible to get off without damaging the roots since the roots have gone clear through the Styrofoam.

Enough of the bad… How about some good reasons?

Styrofoam will not absorb salts, as other potting material will. One big problem with the bark mix and especially sphagnum moss is that it will retain excess salt and cause a chemical build-up in the potting medium. This makes the potting medium decompose faster and decay. You can tell if your orchid has a slat build up if it is sparkling white “glitter” on the top of your plant.

Since the water will enter and exit quickly—almost too quickly—there is no risk of salt build-up. One positive point for Styrofoam. 😊

Reason number 2: Adequate air space for roots. Most potting material fails at this test. Sphagnum moss is the worst. The medium is packed so tightly that the roots can’t breathe.

Orchids don’t have roots like other household plants; they have adapted to live in the nicks and crannies of trees, and from there, absorb air, water, and minerals in the environment. If your orchid is jammed into a pot and can’t breathe, it suffocates.

The Styrofoam pellets will offer adequate airflow since their shape enhances that quality.
The roots will hardly suffer from root rot, or toxic build-up from lack of gas exchange.

After all this, if you still want to try Styrofoam…

First, chose a Styrofoam that isn’t biodegradable. There are two kinds of Styrofoam on the market: one made of cornstarch which dissolves instantly when in contact with water, and the other not. Test your peanuts, but submerging them in water. If they start to deform and rumble, don’t use them.

Always choose the white Styrofoam pellets as compared to pink or green. The pink ones (especially the pink ones) have a specific dye in them that aids in anti-static but is toxic to the orchid. When watered, these will leach out the toxins and slowly kill the roots.

The green ones are variable: some have it, others don’t. Yet how to know which ones do? To avoid any chance of getting toxic dye on your orchid, just avoid all together the colored Styrofoam peanuts in your orchid’s potting media.

The green Styrofoam peanuts are not as toxic, but are made from recycled materials. This is the cause of the green color. Yet, in all honesty, what recycled material was it? It could be a thousand things.

To provide drainage, you’ll need to add stronger pebbles or even rocks to the bottom of your pot. You can add a layer of Styrofoam above them, just so the pot is stable and the roots won’t wiggle around every time you touch the pot.

To properly fertilize, you’ll need to sit your orchid in a bucket of water with the fertilizer. The roots will have to soak in this water for a few minutes to be effective, then you can drain the pot. Otherwise, the fertilizer will just be wasted.
Further Reading Suggestions:

Don't just take my word for what is written here. Continue researching other articles about Styrofoam peanuts in orchid potting media, because everyone has a different point of view and unique techniques that work for them. Here are a few other articles from other websites if you'd like to continue your research on Styrofoam and orchids:

"Styrofoam and Orchidswritten by Sue Bottom,  published by St. Augustine Orchid Society has interesting pictures and very informative explanations about Styrofoam in the potting medium. I'd definitely check out her article.

"Abbott Laboratories staff assist in the recovery of the eastern prairie fringed Orchid" written by Cathy Pollack, published on US Fish & Wildlife Services talks about using Styrofoam but for another purpose in orchid cultivation. With the help of volunteers, the Styrofoam is used for hand pollinating orchids and stabilizing them with toothpicks.

Title: "Pest Management Strategic Plan for Potted Orchid Production in Hawai‘i" written by Mike Kawate and Kelvin T. Sewake, published by National Integrated Pest Management talks about the perfect medium for an orchid, and in the list includes Styrofoam.

They state that "the medium must be pathogen-free and have a good balance of moisture-holding capacity, drainage and aeration. The tender young roots require moisture, but also need good drainage and aeration to prevent anaerobic conditions which will suffocate root tissue and promote the growth of certain bacteria, algae, and other micro-organisms. Available materials include “orchid bark” (usually fir bark, packaged in coarse, medium or fine grade), peat and perlite mixes, coconut chunks (coir), tree-fern (hapu‘u) fiber, sphagnum moss, perlite, Styrofoam, and charcoal." The link above will take you to the 143-page PDF file.
I have never personally used Styrofoam peanuts, not as a potting medium at least. Maybe as a packing medium though, and many online stores will use them to not damage the tender blossoms.

Some orchid growers though have had more luck with Styrofoam as a potting medium; each method is different. That is why you need to gather information first, test and try what works for you, and finally, choose a method that works for you.

Happy Cultivating!
Signature Amanda Matthews
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