3 Myths about Gardening with Styrofoam Debunked

Piece of styrofoam lying in a field in early spring

Talk to any gardener, and they will probably share at least one tip with you about how they use Styrofoam in their garden. Whether they have a flower bed, a veggie garden or even a container garden, there is a good chance they make use of Styrofoam in one way or another. And if they don’t, they probably still have a few Styrofoam gardening tips they learned from someone else that they would be more than happy to share with you.

Styrofoam has been used in gardens in different ways for nearly as long as the material has existed. While there are some scientific facts surrounding the use of this material in gardens, there is also a good bit of fiction. Let’s examine some of the most common myths about gardening with Styrofoam to separate the truth from the old wives’ tales.

White polystyrene balls on red tablecloth

Myth #1: Styrofoam Improves Drainage in Containers

Whether you have a few flowers planted in pots or you have an entire vegetable garden in containers, you have probably heard that adding Styrofoam to the bottom of the container helps improve drainage. Gardeners have used foam packing peanuts for this purpose for decades, but does it really do any good?

The answer: Not really. In fact, if you are using a pot with little to no drainage, adding Styrofoam packing peanuts could do more harm than good. Deep plant roots can grow into the foam material, and without sufficient drainage, they can become waterlogged and rot or die.

Because the synthetic material used in traditional Styrofoam peanuts contains no nutrients, it provides no value to the growing plant. Bio-degradable packing peanuts are made from natural materials, but they will absorb water and break down, providing no benefits in terms of drainage.

Myth #2: Styrofoam Helps Keep Soil Loose and Aerated

If you have ever purchased potting soil that contained squishy white balls, you may have assumed that they were made from Styrofoam.

The answer: No. While these materials are used to prevent potting soil from retaining too much water and becoming too dense, they are not made from the foam material that they are commonly mistaken for.

The white, foam-like balls in your potting soil are there to help keep soil loose and aerated, but they are most commonly made from a naturally occurring volcanic glass known as perlite. When heated to 1,600 degrees Fahrenheit, the glass puffs up like popcorn, resulting in the Styrofoam-like appearance. While it does not absorb moisture, it holds it in tiny cavities around the outside. This makes water readily available to nearby plant roots.

Vermicompost fertilizer perlite

Unlike Styrofoam, the perlite beads decompose naturally over time. As a result, they do not pose any threat to the environment. If you put Styrofoam in your garden, it will not decompose for millions of years. It may also take on moisture and become waterlogged, resulting in soil compression. It could even float away during heavy rains and make its way into a body of water. Styrofoam accounts for a significant portion of ocean pollution, and keeping it out of your garden is one way to avoid contributing to this ever-growing problem.

Myth #3: Styrofoam Cones Keep Roses Warm During the Winter

When cold weather approaches, gardeners grow concerned about keeping their plants — especially delicate ones like roses — safe and warm. Styrofoam cones marketed as “rose cones” have become popular in recent years, but do they really do anything to keep plants warmer when the temperature outside plummets?

The answer: Yes and no. Styrofoam acts as insulator, so temperature fluctuates faster outside of the box than inside. If the outside air suddenly warms up, the air under the cone will actually be colder. However, on most days, the air inside does stay slightly warmer. The Styrofoam also helps protect the plant from wind. It’s important to note, though, that it will not keep the air inside above freezing during extremely cold weather. And in many instances, the temperature difference inside the cone is not significant enough to really make a difference in terms of plant health.

The cones are easily damaged, especially by heavy snow. Fragments can break off and find their way into the environment. For all the benefit they may provide, they aren’t really worth the potential environmental risk.

Closing Thoughts

Styrofoam is an extremely versatile material that can be used for numerous applications. From packaging peanuts that protect merchandise while in transit to insulation in homes and more, it is useful in numerous situations. Because of its negative impact on the environment, however, your garden is one place it probably does not belong.


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