Polystyrene Boxes In The Garden: Yes Or No?

Tomato seedlings in polystyrene
Image by Aris Papachristou

Many gardeners like to get creative and use different things for their containers. A popular container to use in vegetable gardening is a polystyrene box. With all the new information and research being done into plastics, health, and the environment, the big question to ask is: is it safe to grow vegetables in polystyrene boxes?

The answer is probably not. While it is approved food safe for many uses, polystyrene is a potentially harmful substance that can have negative impacts on people’s health and the environment. Many countries around the world are working on banning polystyrene completely.

Polystyrene boxes do have many benefits for your plants. However, do these benefits outweigh the health and environmental risks associated with them? Lets look into this in detail.

What Is Polystyrene?

Polystyrene is a type of plastic used in a variety of products. Most people think of it as the white foam packaging that comes around appliances and electronics, but it can also be solid and is used in a number of hard plastics. To tell if a product is made of polystyrene, turn the plastic item over and look on the bottom for three arrows chasing each other in a triangle. The number inside this symbol is called the Resin Identification Code and products made from polystyrene will show a #6.

Is Styrofoam the same as polystyrene?

These two terms are commonly used interchangeably, but this is slightly inaccurate. Styrofoam is a trademarked brand of a certain type of polystyrene. So, yes, Styrofoam is polystyrene. However, all polystyrene is not Styrofoam.

In the garden, many people use large polystyrene boxes for their planters. In this article, we are going to consider polystyrene items such as Styrofoam coolers, but it is important to note that many plant pots that you buy are also made from polystyrene. However, polystyrene has been found to leach far less from hard plastics than it does from soft foam containers, but many of the points we will discuss might apply to plant pots as well.

While polystyrene box planters do have benefits to your plants, there are many health and environmental problems that should be considered before you start your garden in them.

The Health Impact

The Food and Drug Administration in the US has approved polystyrene as food safe, meaning that it can come into contact with food during manufacturing, transportation, and storage. Some types of polystyrene are even approved as a food additive. However, #6 plastic is listed as a material to avoid in most situations, and especially where food is concerned.

Styrofoam cup Photo by Caleb Lucas on Unsplash
Photo by Caleb Lucas on Unsplash

Styrene is the main ingredient used to make polystyrene, and styrene has been shown in many studies to be a carcinogen to both humans and animals. Other studies have shown that chemicals from polystyrene leach into food, and this is particularly true if the products are heated, and when liquid is present.

In the garden, a polystyrene box would be watered and exposed to the sun. It can reach very high temperatures and this can be a potential source of carcinogens in your food, especially in the middle of summer.

The Environmental Impact

Many countries around the world are looking to ban polystyrene because of the impact it has on the environment. Canada, the UK, and Australia as well as many cities around the US are all looking at banning single-use plastics and this includes polystyrene. In most places, polystyrene is not recyclable, and most of it is thrown away. A lot of it ends in landfills, but it also pollutes land and the waters. Polystyrene is a major polluter of the oceans and can cause serious danger to marine life as it breaks down into millions of small white balls.

On top of that, polystyrene can take nearly 500 years to decompose. Even if we do repurpose it in our gardens, our decision to use polystyrene will be around for centuries.

Are There Benefits To Growing In Polystyrene Boxes?

Why would I grow in polystyrene boxes? Are there any benefits for it in my garden?

Yes, polystyrene does have many advantages as a planter. They are lightweight and easy to move to give you great flexibility in your container garden. They are also readily available and very inexpensive. You can often get them secondhand for free from fish markets or grocery stores that would otherwise throw them away.

Polystyrene boxes can also benefit your plants. Since polystyrene is a key ingredient in insulation, if used as garden boxes it will insulate the soil and can keep the roots of your plants from freezing. The material is also waterproof and will effectively retain moisture and keep your plants from drying out. (Because of this, it is imperative to poke drainage holes in the bottom of the container, and raise the box off the ground to allow excess water to drain away.)

Do The Benefits Outweigh The Dangers?

Maybe you are moving in the middle of the growing season, and polystyrene offers the best mobility for your garden. Using recycled boxes that a store would otherwise throw away helps keep plastic out of the landfill and does something useful with it. Perhaps polystyrene offers the best cold protection for your plants in your area, or it will help you through a serious drought.

All of these benefits, however, must be balanced against the health and environmental concerns. Food self-sufficiency is about providing your own food without relying on the external support, but our self-sufficient garden should also not cause damage to the outside world.

Some people swear by polystyrene boxes in the garden. Others won’t have anything to do with them. Whatever you choose is up to you, and you must make the best decision for your garden and your own food.

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About the Author Harry Thompson

Involved in home renovations throughout his life, Harry is an expert in everything to do with home and garden DIY. In his spare time, he enjoys cooking and tending to his garden.