Is It Safe to Use Styrofoam in Planters for Herbs?

Container gardening lets gardeners grow vegetables in tiny spaces like balconies and patios. In addition, it gives gardeners the flexibility to move the containers based on the weather, such as sliding them under the overhang during a potentially damaging thunderstorm. Huge containers frequently require filler in the seams, and foam chunks or peanuts can fulfill that requirement without causing injury to people who eat the vegetables.

How Foam Helps

When using large containers, you need a large amount of dirt to fill them from top to bottom. That gets expensive fast, and you find yourself paying for dirt you don’t require. (Most vegetables just require between 8 and 6 inches of dirt, so any dirt deeper than that’s a wasted expense.) Including a few inches of foam peanuts or chunks at the bottom of the container lowers the amount of soil needed to fill out the planter. Additionally, the foam keeps dirt from washing out of the drainage holes while assisting with drainage by keeping the soil from compacting at the base of the pot.

Foam Controversy

Because foam is just a man-made material, concerns have arisen about substances leaching from foam to the soil and contaminating plants. Styrene, part of the polystyrene chemical that makes up most food-service and packing foams, brought concern from consumers after the National Toxicology Program recorded it as a possible carcinogen — or even cancer-causing representative — at the 2011 12th Report on Carcinogens. The report also says, however, that foam is safe to use around food; the risk lies with workers in industrial facilities that construct items such as boats using styrene.

How to Use Memory

The size of the container along with the vegetables you are growing dictate how much foam to add to the pot. Many vegetables require about 6 inches of dirt, so if you’ve got a pot 12 inches deep, you can fill it up with foam chunks or peanuts. With vegetables wanting 8 inches of dirt, don’t use over 3 or even 4 inches of foam at a grass 12 inches deep. After adding the foam, amount it slightly with your hand so 1 side isn’t much higher than another, allowing for even root growth. Pour dirt over the foam, and also plant the vegetables. Water and attention for those vegetables as ordinary; the foam helps with drainage in the base of the pot but does not alter soil density or even the plants’ needs in any way.

Bottom Line on Foam

Foam does not break down readily in the environment, which means it is unlikely to degrade in a vegetable gardening container so it’s safe to use as filler. Although some chemicals in the foam can leach out if it gets overheated — such as when you heat a foam cup of coffee in the fridge — it does not leach chemicals under normal temperature conditions, in accordance with Dr. Andrew Weil, a leader in the field of integrative medicine. The dirt in the container — and thus the foam below the dirt — does not become hot enough to cause a problem since it typically stays cooler than the ambient temperature.

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